Showing papers in "Journal of Chemical Technology & Biotechnology in 2013"

A brief review on hydrometallurgical technologies for recycling spent lithium‐ion batteries

Abstract: Lithium-ion battery is a mature technology that is used in various electronic devices. Nowadays, this technology is a good candidate as energy storage for electric vehicles. Therefore, much research is focused on the development of high-density power lithium-ion batteries. Government regulations force manufacturers to recycle the batteries for safety and health reasons but recycling could also be interesting from an economic viewpoint since cathodes in lithium-ion batteries contain valuable metals. The electrodes in lithium-ion batteries will evolve to provide more energy and the recycling processes will have to fit with this evolution. Leaching, bioleaching and solvent extraction are at the centre of these processes. In this paper, recent leaching and solvent extraction strategies for recovering valuable metals from spent lithium-ion batteries are reviewed and the evolution of these processes is discussed. © 2013 Society of Chemical Industry

Degradable natural polymer hydrogels for articular cartilage tissue engineering

Abstract: Articular cartilage has poor ability to heal once damaged. Tissue engineering with scaffolds of polymer hydrogels is promising for cartilage regeneration and repair. Polymer hydrogels composed of highly hydrated crosslinked networks mimic the collagen networks of the cartilage extracellular matrix and thus are employed as inserts at cartilage defects not only to temporarily relieve the pain but also to support chondrocyte proliferation and neocartilage regeneration. The biocompatibility, biofunctionality, mechanical properties, and degradation of the polymer hydrogels are the most important parameters for hydrogel-based cartilage tissue engineering. Degradable biopolymers with natural origin have been widely used as biomaterials for tissue engineering because of their outstanding biocompatibility, low immunological response, low cytotoxicity, and excellent capability to promote cell adhesion, proliferation, and regeneration of new tissues. This review covers several important natural proteins (collagen, gelatin, fibroin, and fibrin) and polysaccharides (chitosan, hyaluronan, alginate and agarose) widely used as hydrogels for articular cartilage tissue engineering. The mechanical properties, structures, modification, and structure–performance relationship of these hydrogels are discussed since the chemical structures and physical properties dictate the in vivo performance and applications of polymer hydrogels for articular cartilage regeneration and repair. © 2012 Society of Chemical Industry

Ionic liquids and deep eutectic solvents for biodiesel synthesis: a review

Abstract: During the past decade, ionic liquids (ILs) have gained tremendous attention in nearly every branch of the chemical and physical sciences as designer (task-driven) and budding ‘green’ solvent alternatives to conventional volatile organics. In particular, with a more in-depth understanding of their physicochemical properties, the active exploration of ILs as alternative solvents and/or catalysts in the chemical or enzymatic (biocatalytic) production of biodiesel has gained momentum. Most excitingly, very recent developments in the science of deep eutectic solvents (DESs) have initiated potentially more cost-effective approaches to biodiesel synthesis. At this stage, there is sufficient research completed to provide an important opportunity to stand back and assess the progress in the field, critically examining the strengths and limitations for IL and DES technology in biodiesel synthesis. No such comprehensive evaluation exists. This work, therefore, seeks to bridge this gap by systematically reviewing the reported methods for biodiesel production which make use of ILs, either as (co)solvent components or catalysts, highlighting existing problems and limitations, with an emphasis placed on the future research required to bypass the hurdles to employing ILs in commercial biodiesel production. Copyright © 2012 Society of Chemical Industry

The integration of flow reactors into synthetic organic chemistry

Abstract: The material presented in this review is based upon discussions and interactions with members of the Department of Chemistry and Biochemistry within the University of Windsor, Ontario, Canada. This article explores the changing face of chemical synthesis with regard to the impact of flow based chemical processing technologies. Highlighted works from the Innovative Technology Centre (ITC), Cambridge, UK, are used to illustrate the alternative synthetic practices available to modern research chemists. The dominant theme of the review is the synergistic effects encountered by combining the advantages of continuous processing regimes with the power of immobilized reagents and scavenger systems for multi-step organic chemistry. © 2012 Society of Chemical Industry

Recent advances in microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) for wastewater treatment, bioenergy and bioproducts

Abstract: Bioenergy is a renewable energy that plays an indispensable role in meeting today's ever increasing energy needs. Unlike biofuels, microbial fuel cells (MFCs) convert energy harvested from redox reactions directly into bioelectricity. MFCs can utilize low-grade organic carbons (fuels) in waste streams. The oxidation of the fuel molecules requires biofilm catalysis. In recent years, MFCs have also been used in the electrolysis mode to produce bioproducts in laboratory tests. MFCs research has intensified in the past decade and the maximum MFCs power density output has been increased greatly and many types of waste streams have been tested. However, new breakthroughs are needed for MFCs to be practical in wastewater treatment and power generation beyond powering small sensor devices. To reduce capital and operational costs, simple and robust membrane-less MFCs reactors are desired, but these reactors require highly efficient biofilms. Newly discovered conductive cell aggregates, improved electron transport through hyperpilation via mutation or genetic recombination and other advances in biofilm engineering present opportunities. This review is an update on the recent advances on MFCs designs and operations. © 2012 Society of Chemical Industry

Recent Development in Chemical Depolymerization of Lignin: A Review

Abstract: This article reviewed recent development of chemical depolymerization of lignins. There were five types of treatment discussed, including base-catalyzed, acid-catalyzed, metallic catalyzed, ionic liquids-assisted, and supercritical fluids-assisted lignin depolymerizations. The methods employed in this research were described, and the important results were marked. Generally, base-catalyzed and acid-catalyzed methods were straightforward, but the selectivity was low. The severe reaction conditions (high pressure, high temperature, and extreme pH) resulted in requirement of specially designed reactors, which led to high costs of facility and handling. Ionic liquids, and supercritical fluids-assisted lignin depolymerizations had high selectivity, but the high costs of ionic liquids recycling and supercritical fluid facility limited their applications on commercial scale biomass treatment. Metallic catalyzed depolymerization had great advantages because of its high selectivity to certain monomeric compounds and much milder reaction condition than base-catalyzed or acid-catalyzed depolymerizations. It would be a great contribution to lignin conversion if appropriate catalysts were synthesized.

A review: production of activated carbon from agricultural byproducts via conventional and microwave heating

Abstract: Productionofactivatedcarbon(AC)fromagriculturalbyproductsis a researchfieldthathas gainedincreased interestin recent years because of its potential for the disposal of agro-residues. At the same time, a beneficial byproduct that can be used in a number of environmental applications is produced. This paper surveys the developments in the production processes of AC fromagriculturalbyproductsinthepast7yearsfrom2005to2012viaconventionalandmicrowaveheating.Emphasisisplaced on the applied methodology and the influences of activating conditions, such as carbonization temperature, retention time, and impregnation ratio. From the review of AC production processes, agricultural wastes produced by a chemical method with microwave heating can be a source of AC with relatively higher surface area than that produced via conventional heating. c � 2013 Society of Chemical Industry Supportinginformationmaybefoundintheonlineversionofthisarticle.

Biological synthesis of copper nanoparticles using Magnolia kobus leaf extract and their antibacterial activity

Abstract: Bakground Biological methods for metal nanoparticle synthesis using plant extracts have been suggested as possible ecofriendly alternatives to chemical and physical methods. In the present study, copper nanoparticles were biologically synthesized using Magnolia kobus leaf extract as reducing agent and their antibacterial activity was evaluated against Escherichia coli. Results On treatment of aqueous solution of CuSO4·5H2O with Magnolia kobus leaf extract, stable copper nanoparticles were formed. UV–vis spectroscopy was used to monitor the quantitative formation of copper nanoparticles. The synthesized nanoparticles were characterized with inductively coupled plasma spectrometry (ICP), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM). Electron microscopy analysis of copper nanoparticles indicated that they ranged in average size from 37 to 110 nm. Antibacterial tests were carried out by counting viable E. coli cells after 24 h growth in shake flasks containing latex foams coated with copper nanoparticles. As a result, foams coated with biologically synthesized copper nanoparticles showed higher antibacterial activity compared with foams untreated and foams treated with chemically synthesized copper nanoparticles using sodium borohydride and Tween 20. The antibacterial activities were inversely proportional to the average nanoparticle sizes. Conclusion The present results show that stable copper nanoparticles can be ecofriendly synthesized using Magnolia kobus leaf extract, offering an inexpensive alternative to antibacterial silver nanoparticles. © 2013 Society of Chemical Industry

Hydrothermal catalytic production of fuels and chemicals from aquatic biomass

Abstract: One of the promising avenues for biomass processing is the use of water as a reaction medium for wet or aquatic biomass. This review focuses on the hydrothermal catalytic production of fuels and chemicals from aquatic biomass. Two different regimes for conversion of aquatic biomass in hydrothermal conditions are discussed in detail. The first is hydrothermal liquefaction, and the second is hydrothermal gasification. The goals of these processes are to produce liquid-fuel-range hydrocarbons and methane or hydrogen, respectively. The catalytic upgrading of biocrude resulting from noncatalytic liquefaction and the stability and degradation of catalysts in high temperature water are also discussed. The review concludes with a brief discussion of the outlook for and opportunities within the field of hydrothermal catalytic valorization of biomass. Copyright © 2012 Society of Chemical Industry

Magnesium ammonium phosphate formation, recovery and its application as valuable resources: a review

Abstract: To address the issues of wastewater treatment and depleting phosphorus (P) resources, the present review focuses on the very wide interest in P recovery from wastewater, with scientific research underway in countries across the globe. The study describes the growing concern for diminishing P resources and then the chemical principle of magnesium ammonium phosphate (MAP) precipitation, factors influencing MAP crystallization, and various developments achieved through bench, pilot and full scale MAP reactors. A brief description is given of MAP purification and dissolution to economically exploit MAP as a phosphate and magnesium source. Experience in re-use of recovered MAP as a sustainable agriculture fertilizer is discussed including pot and field trials. © 2012 Society of Chemical Industry

Naturally Occurring Xanthones: Chemistry and Biology

Abstract: Xanthones are one of the biggest classes of compounds in natural product chemistry. A number of xanthones have been isolated from natural sources of higher plants, fungi, ferns, and lichens. They have gradually risen to great importance because of their medicinal properties. This review focuses on the types, isolation, characterization, biological applications, and biosynthesis of naturally occurring xanthones isolated so far. Different physicochemical and instrumental methods such as liquid-solid and liquid-liquid extraction, TLC, flash chromatography, column chromatography, IR, 1H NMR and 13C NMR spectroscopy, GLC, HPLC, GC, and LCMS have been widely used for isolation and structural elucidation of xanthones. Hepatoprotective, anticarcinogenic, antileprosy, antimalarial, antioxidant, anticholinergic, mutagenicity, radioprotective, immunomodulatory, antibone resorption, antiparasitic, neuraminidase inhibitory, anticomplement, antibacterial, antifungal, algicidal, anti-HIV, cardioprotective, antitumoral, antidiabetes, antihyperlipidemic, antiatherogenic, anti-inflammatory, antiulcer, antidiabetic, hypolipidemic, analgesic, antiasthmatic, antihistaminic, antiamoebic, diuretic, antidiarrheal, larvicidal, and ovicidal activities have been reported for natural occurring xanthones. To a certain extent, this review provides necessary foundation for further research and development of new medicines.

Removal of ammonium, iron and manganese from potable water in biofiltration units: a review

Abstract: Ammonium, and trace metals such as iron and manganese are common inorganic pollutants present in waters. Several surface and groundwaters contain natural or increased concentrations of these pollutants that are observed either isolated or in pairs, or all three together. Although several processes have been established for the biological removal of one of the above-mentioned pollutants, only recently have important studies been performed on the efficient and cost-effective simultaneous biological removal of two or more substances. This paper reviews the variety of full- and pilot-scale biological filters that have been used for combined or simultaneous biological removal, as well as factors and conditions that were found to affect the process. The main results regarding research progress on combined or simultaneous biological removal are evaluated. Finally, the kinetic models and simulation approaches used are discussed. © 2013 Society of Chemical Industry

Role of lignin in a biorefinery: separation characterization and valorization

Abstract: Lignin, a major component of the cell wall of vascular plants, has long been recognized for its negative impact and treated as a by-product in a biorefinery. This highly abundant by-product of the biorefinery is undervalued and underdeveloped due to its complex nature. The development of value-added products from lignin would greatly improve the economics of the biorefinery. The inherent properties of lignin significantly affect the productivity of the biorefinery processes and its potential applications. Although the structure and biosynthetic pathway of lignin have been studied for more than a century, they have not yet been completely elucidated. In this mini-review, the primary obstacles to elucidating the structure of native lignin, including separation and characterization, are highlighted. Several classical methods for separation and various NMR techniques, especially 2D HSQC NMR, for characterization of lignin are reviewed. Some potential applications of lignin are introduced. It is believed that a knowledge of the method to separate lignin from the cell wall and structural features of the lignin polymer from lignocellulosic materials will help to maximize the exploitation of lignocelluloses for the biorefinery as well as the utilization of lignin for novel materials and chemicals. © 2012 Society of Chemical Industry

Biohydrometallurgy of secondary metal resources: a potential alternative approach for metal recovery

Abstract: Research on biohydrometallurgy of secondary metal resources is primarily focused on the leaching of valuable metals. For secondary metal resources biological processing can be an economically more effective and environmentally friendlier alternative to traditional hydrometallurgical and pyrometallurgical processes. Therefore, biohydrometallurgy is a rapidly evolving biotechnology that has already provided revolutionary solutions to old problems associated with recovery of metals by conventional pyrometallurgy and chemical metallurgy. This review evaluates various processes of recovery of metals from waste materials and commercial applications are discussed. Case studies and future technology directions are reviewed. © 2013 Society of Chemical Industry

New lignocellulose pretreatments using cellulose solvents: a review

Abstract: Non-food lignocellulosic biomass is the most abundant renewable bioresource as a collectable, transportable, and storable chemical energy that is far from fully utilized. The goal of biomass pretreatment is to improve the enzymatic digestibility of pretreated lignocellulosic biomass. Many substrate factors, such as substrate accessibility, lignin content, particle size and so on, contribute to its recalcitrance. Cellulose accessibility to hydrolytic enzymes is believed to be the most important substrate characteristic limiting enzymatic hydrolysis. Cellulose solvents effectively break linkages among cellulose, hemicellulose and lignin, and also dissolve highly-ordered hydrogen bonds in cellulose fibers accompanied with great increases in substrate accessibility. Here the history and recent advances in cellulose solvent-based biomass pretreatment are reviewed and perspectives provided for addressing remaining challenges. The use of cellulose solvents, new and existing, provides opportunities for emerging biorefineries to produce a few precursors (e.g. monosaccharides, oligosaccharides, and lignin) for the production of low-value biofuels and value-added biochemicals. c � 2012 Society of Chemical Industry

The importance of key operational variables and electrolyte monitoring to the performance of an all vanadium redox flow battery

Abstract: BACKGROUND The all vanadium redox flow battery (VRFB) has become the most common type of rfb, however, it is essential to improve our understanding of the importance of key operational variables, including electrode materials, electrolyte flow rate, current density and temperature, on the cell efficiency together with improved methods for cell monitoring. RESULTS Several carbon felts were characterized for their electrode activity. A commercially supplied electrolyte of unknown composition was analysed and was shown to contain a VO2+: V3+ ratio of 4.8:1 (total vanadium species = 1.5 mol dm−3) in 4 mol dm−3 H2SO4. A battery (100 cm2) was assembled using three-dimensional carbon felts and planar carbon feeders as the electrodes with a Nafion® 115 proton exchange membrane. Performance was examined using electrolytes of varying vanadium ion concentration at volumetric flow rating from 0.5–3 mL min1. A suitable volumetric flow rate of electrolyte through each half-cell was found to be in the range 1.5–2.0 mL min−1, corresponding to a mean linear electrolyte velocity of 1.0–10.1 cm s−1 through the carbon felt electrode. At a constant current charge and discharge current density of 100 mA cm−2 the typical voltage efficiencies were 65%. Charge-discharge curves were then simulated using a detailed physical model, which generated good quantitative agreement with experimental cell performance. CONCLUSIONS This study has quantified the effect of key process variables on cell efficiency. A mathematical model has been used successfully to describe charge-discharge performance and the use of open-circuit cell voltage has been shown to provide a simple and useful means of cell monitoring. Copyright © 2012 Society of Chemical Industry

Quantitative structural characterization and thermal properties of birch lignins after auto-catalyzed organosolv pretreatment and enzymatic hydrolysis.

Abstract: BACKGROUND: To achieve the goals of economically feasible auto-catalyzed organosolv pretreatments in bioethanol production, chemical conversion of the isolated lignin is needed. However, the structures and properties of lignin molecules produced after pretreatment have not been thoroughly investigated before its effective utilization. RESULTS: The study focused on the auto-catalyzed ethanol – water pretreatment of southwest birch, with the aim to clarify the structural transformations of birch lignin after pretreatment. Chemical structural elucidation of the isolated lignins was performed using multiple NMR methodologies ( 31 P-, 13 C- and 2D-HSQC NMR techniques). Results showed that the amount of β-O-4 linkages decreased in the order of AEOL (auto-catalyzed ethanol organosolv lignin) < EHLP (enzymatic hydrolysis lignin, pretreated) < EHLU (unpretreated). The homolytic cleavage of β-O-4 linkages resulted in an increase of free phenolic hydroxyl groups and carboxylic acids in AEOL and EHLP compared with that of EHLU. In addition, α-ethoxylation was the only modification in the auto-catalyzed ethanol organosolv pretreatment (AEOP). Moreover, the thermal stability of the lignin samples is related to its inherent and condensed structures. CONCLUSIONS: These findings would facilitate the further utilization of lignin as starting material for developing value-added products in chemical and catalytic process. c � 2013 Society of Chemical Industry

Influence of pig slurry characteristics on ammonia stripping efficiencies and quality of the recovered ammonium-sulfate solution.

Abstract: BACKGOUND Proper treatment technologies are required to address the environmental issues associated with increasing volumes of slurries. Ammonia stripping reduces the nitrogen content of the slurries and allows for its recovery in a valuable form. Herein the influence of pig slurry characteristics on ammonia stripping efficiency and the quality of the recovered ammonia solution were assessed. RESULTS Substrates characterized by low organic matter content, below 10 g COD L-1, resulted in ammonia stripping efficiencies greater than 80%. Changing slurry pH to 9.5 significantly improved the process, even though high COD contents kept the efficiencies below 70%. Ammonium sulfate solutions could be concentrated up to nitrogen contents greater than 40 g N L-1, while maintaining low organic contamination. Introducing a basic trap (pH > 12) before the acid one, allowed for the retention of more than 60% of the stripped organics with less than 3% of the stripped ammonia. CONCLUSIONS Ammonia stripping coupled with absorption proved to be a suitable technical solution for the recovery and valorization of the nitrogen contained in pig slurries. Clear enhancements in process efficiency were observed in the case of slurries with low organic matter content. The introduction of a basic trap, together with a slight increase in the operational pH level, further increased organics abatement. © 2012 Society of Chemical Industry

Tetracycline degradation and mineralization by the coupling of an electro‐Fenton pretreatment and a biological process

Abstract: BACKGROUND Studies on the degradation and mineralization of tetracycline by means of the electro-Fenton process are lacking in the available literature. Its relevance as a pre-treatment prior to a biological process for the removal of tetracycline was therefore examined. RESULTS Degradation followed pseudo-first-order kinetics and the optimal operating conditions were: 0.1 mmol L-1 catalyst (Fe2+) concentration, 300 mA applied current intensity and 25 mg L-1 tetracycline, leading to total degradation within only 5 min and a mineralization yield of 89 % after 6 h electrolysis. Biodegradability tests were realized with 100 mg L-1 tetracycline; BOD5/COD ratio increased from 0.02 to 0.56 after 6 h electrolysis, showing the relevance of the electro-Fenton pre-treatment. However, to keep a significant residual organic content, 2 to 4 h electrolysis time may be more relevant, leading to BOD5/COD ratio and mineralization yields of 0.33–0.44 and 46–72%, respectively. CONCLUSION Activated sludge cultures of pretreated and non-pretreated tetracycline solutions were carried out for 3 weeks. The overall TOC removal increased from 28% for the non-pretreated tetracycline to 68 and 86% after 2 and 4 h electrolysis, confirming the efficiency of the proposed combined process. © 2012 Society of Chemical Industry

Bioremediation of nitrate-polluted groundwater in a microbial fuel cell

Abstract: BACKGROUND Groundwater quality is threatened by nitrate accumulation in several regions around the world. Nitrate must be removed from contaminated groundwater to use it as drinking water. Microbial fuel cells (MFCs) can be used for autotrophic denitrification. Thus, the use of MFCs is a potential alternative to using traditional methods for treating nitrate-polluted groundwater. RESULTS The objective of this study was to evaluate the potential of MFC technology to treat nitrate-polluted groundwater (28.32 ± 6.15 mgN-NO3− L−1). The bioanode was fed with an acetate solution that permitted electron and proton flux to the biocathode. Initially, nitrite was observed in the effluent. After 97 days of operation, the denitrifying-MFC reduced the nitrate and nitrite concentrations in the effluent (12.14 ± 3.59 mgN-NO3− L−1 and 0.14 ± 0.13 mgN-NO2− L−1).Thus, this method improved water quality to meet World Health Organisation standards. However, nitrous oxide emissions were deduced from the electron balance, cathode coulumbic efficiency and Tafel plots. Bioelectrochemical evolution of the biocathode was related to the denitrification nature (sequential reaction steps from NO3− to N2, through NO2− and N2O as stable intermediates) and was supported by the Tafel plots. CONCLUSION The bioremediation of nitrate-polluted groundwater with a MFC biocathode is feasible. © 2012 Society of Chemical Industry

Degradation of tetracyclines in different water matrices by advanced oxidation/reduction processes based on gamma radiation

Abstract: Background This study analyzes the efficacy of a gamma radiation advanced oxidation/reduction process (AORP) to treat waters contaminated with the antibiotics tetracycline (TC), chlortetracycline (CTC), and oxytetracycline (OTC). Results Study results indicate that: (1) radiolysis of the three TCs fits a pseudo-first-order kinetic model in which the radiation-chemical yield decreases with higher absorbed dose; (2) the value of the dose constant depended on the dose rate, which ranged from 3.83 to 1.66 Gy min–1, and depended to a small extent on the medium pH between pH values of 2.0 and 10.0, since aqueous electrons and hydroxyl radicals both act in TC degradation; (3) the effectiveness of the process was slightly increased at low concentrations of H2O2; (4) the presence of Cl−, , , and humic acid influenced TCs degradation, which was higher at low concentrations of Cl−, and HA and markedly decreased at low concentrations of of and ; (5) the dose constant is lower in natural waters; (6) TOC values for ultrapure water, surface water, groundwater and wastewater showed that it is not possible to obtain complete TC mineralization at the absorbed doses; (7) the toxicity of byproducts formed during the radiolytic process was lower. Conclusions Gamma radiation, an oxidation/reduction procedure, is an effective treatment for removing TC, CTC and OTC from aqueous solutions. TC degradation takes place by both oxidation and reduction pathways, with a predominance of the latter, as demonstrated by the markedly reduced dose constant in the presence of aqueous electron scavengers.

Biolubricant synthesis from waste cooking oil via enzymatic hydrolysis followed by chemical esterification

Abstract: BACKGROUND Lubricants manufactured conventionally from non-renewable mineral oil resources are not biodegradable and are liable to cause adverse environmental impacts. Biodegradable vegetable oils present a promising lubricant feedstock alternative. Waste cooking oil (WCO), which otherwise finds no immediate potential utilization can be successfully used to synthesize bio-lubricant. A novel synthetic method was developed by using the two-step process of C. rugosa lipase-mediated hydrolysis of WCO to free fatty acids (FFA) followed by Amberlyst 15H esterification of FFA with octanol. The octyl esters produced was the desired biolubricant. RESULTS The effect of different physico-chemical parameters like temperature, catalyst loading, agitation speed, molar ratio of octanol:FFA and the presence of different desiccants on the esterification reaction was examined. The optimum conditions to get maximum yield of biolubricant in minimum time were, octanol:FFA molar ratio = 3:1, temperature = 80 °C, catalyst = 2 g and desiccant (preferably silica gel powder) = 50% weight of FFA. Fourier transform infrared spectroscopy confirmed that the product formed was ester. CONCLUSION Biolubricant (octyl esters) was prepared efficiently from WCO by the two-step process developed. This novel approach represents a viable means of producing lubricants from wastes which are renewable in nature and can be an alternative to non-renewable mineral oil feedstocks. Copyright © 2012 Society of Chemical Industry

Attached growth systems for wastewater treatment in small and rural communities: a review

Abstract: This paper reviews the application of attached growth processes for municipal wastewater treatment. Attached growth processes are classified as aerobic (either aerated or non-aerated), anaerobic and hybrid (anaerobic/anoxic and aerobic). The main advantage of attached growth systems is that they maintain a high concentration of microorganisms resulting in high removal rates at relatively small hydraulic retention times. The basic design and operational characteristics of various systems are presented in terms of packing materials, organic loading rates, treatment temperature, as well as achieved removal rates. © 2012 Society of Chemical Industry

Hollow-fiber membrane bioelectrochemical reactor for domestic wastewater treatment

Abstract: Background Microbial fuel cells (MFCs) are potentially advantageous as an energy-efficient approach to wastewater treatment; however, the quality of the MFC effluent has not been well addressed. In this study, a membrane bioelectrochemical reactor (MBER) was developed through integrating hollow-fiber ultrafiltration membranes into a tubular MFC to improve the effluent quality. Results This MBER was operated with an acetate solution or domestic wastewater (primary effluent) for more than 200 days. The MBER removed 43–58% of total chemical oxygen demand (COD) from the acetate solution and achieved 30–36% coulombic efficiency. When treating the wastewater, the MBER was able to maintain almost 90% COD removal and an effluent turbidity <1 NTU. A strategy of periodic backwash and membrane relaxation led to a slow increase in the transmembrane pressure (TMP) from zero to 15 kPa in more than 40 days at hydraulic retention time (HRT) 36 h. However, both lower HRTs and high organic loading rates rapidly increased the transmembrane pressure. Conclusion A proof of concept of an MBER was presented and shown to be effective in contaminant removal. Preliminary energy analysis suggests that the MBER could theoretically produce sufficient energy from the acetate solution to support the pumping system. These results demonstrate the feasibility of the MBER concept and the challenges for further development of the MBER system. © 2012 Society of Chemical Industry

Insight into microbial hemicellulases other than xylanases: a review.

Abstract: Hemicellulases responsible for depolymerization of hemicellulose, including α-glucuronidase, α-arabinofuranosidase, arabinase, endo-mannanase, β-mannosidase, acetyl xylan esterase and feruloyl xylan esterase, were reviewed. They usually exist as multimers with a modified (β/α)8 Tim barrel fold. In a few cases they possess a substrate binding domain which helps them bind to the substrates bringing efficient hydrolysis. Post-translational modifications are the major reasons leading to enzyme multiplicities to adapt the heterogeneous nature of hemicellulose. Glycosylation is one of the most important post translational modifications and contributes multiple functions to the protein such as stability, multiplicity and in a few cases enzyme activity. Advances in recombinant DNA technology have made it feasible to clone, improve and functionally express them in various hosts. Hemicellulases are traditionally applied in food, feed, detergent and paper industries, but their applications in hydrolysis of hemicellulose to release sugars is expected to increase, driven by the rapid development of lignocellulose biorefineries. Screening more powerful hemicellulases from nature, mining their coding genes from various sources and engineering them genetically are recommended for broadening their applications. © 2012 Society of Chemical Industry

Performance of the Biocompatible Surfactant Tween 80, for the Formation of Microemulsions Suitable for New Pharmaceutical Processing

Abstract: The aim of this work was to investigate the phase behaviour and the structure of the n-hexane/water emulsions based on a nonionic, nontoxic and biocompatible surfactant, Tween 80. This system is of interest for new pharmaceutical techniques based on supercritical fluids to form nano- and encapsulated particles. However, it showed a lack of stability denoted by large areas of macroemulsion. For this reason, the effect of additives (alcohols and brine) and external variables (temperature) were explored. The replacement of water by brine caused negligible impact due to the nonionic character of Tween 80. On the contrary, the presence of an alcohol (ethanol or 1-butanol) enhanced the solubility of the surfactant in the oil phase and decreased the mixture viscosity, resulting in improved surface activity. Similar results were obtained by raising the temperature until the cloud point was reached (60°C). With these modifications, microemulsions at relatively low concentrations of surfactant (around 30%) and within a broad interval of compositions could be obtained, widening their possible use in pharmaceuticals manufacturing (such as controlled drug delivery, enzymatic reactions, or excipient processing). The understanding of the surfactant performance could be further used to substitute the n-hexane by a greener solvent, such as supercritical CO2.

Effect of immobilization protocol on optimal conditions of ethyl butyrate synthesis catalyzed by lipase B from Candida antarctica

Abstract: Background In this work two immobilized preparations of lipase (EC 3.1.1.3) B from Candida antarctica (CALB) were compared as biocatalysts in the synthesis of ethyl butyrate, a short-chain esters with fruity notes. Commercial Novozym 435 and CALB immobilized on styrene-divinylbenzene beads (MCI-CALB) were tested for esterification reactions. Central composite design and response surface methodology were used to optimize the reaction temperature, substrate molar ratio, enzyme content, and the added water. Results The two enzymatic preparations presented different optimal conditions concerning ethyl butyrate production, with higher yields of conversion around 85% in 1.5 h being achieved. However, MCI-CALB presented productivities 1.6 times higher than Novozym 435. The main difference between the biocatalysts was in relation to operational stability during batch reuse experiments, in which MCI-CALB retained 80% of its initial activity after eight batches, while Novozym 435 retained only 20% under the same conditions. Conclusion It was verified that variations in the protocols for enzyme immobilization causes different optimal conditions for the esterification reaction. These are very interesting results because reaction times were short, producing high conversion yields and productivities considering the mass of biocatalyst used. © 2012 Society of Chemical Industry

Novel applications of dividing-wall column technology to biofuel production processes.

Abstract: Biofuels enjoy nowadays increased public and scientific attention, driven by key factors such as volatile oil price, the need for increased energy security, and concerns over greenhouse gas emissions from fossil fuels. However, in order to make biofuels a competitive alternative, the cost of production has to be significantly reduced by using enhanced process technologies. Distillation is heavily involved in the production processes of biofuels—taking the blame for the high energy requirements that have a negative impact on the operating costs. Dividing-wall column (DWC) is one of the best examples of proven industrial process intensification technology in distillation, as it allows significantly lower investment and operating costs while also reducing the number of equipment units and the carbon footprint. This work presents an overview of novel applications using the DWC technology in the production of the most important biofuels, by employing multi-component separations, azeotropic, extractive or reactive distillation in a DWC: enhanced methanol recovery and glycerol separation in biodiesel production, synthesis of fatty acid methyl esters and dimethyl ether (DME) by reactive distillation, integrated DME purification and methanol or CO2 recovery in the dimethyl ether process, as well as bioethanol concentration and dehydration. The industrially relevant case studies presented here show that significant energy savings are possible (ranging from ∼20 to 60%) while simplifying the processes by using less equipment that requires a lower plant footprint. Remarkably, in most cases there is also the possibility of revamping existing plants producing biofuels, and thus reusing the already available equipment. © 2013 Society of Chemical Industry

Numerical and experimental analyses of planar asymmetric split‐and‐recombine micromixer with dislocation sub‐channels

Abstract: BACKGROUND A passive planar micromixer with dislocation sub-channels, based on the principle of planar asymmetric split and recombination, has been proposed for its effective mixing. Both numerical simulations and experiments were used to design and investigate the effect of parameters and flowing feature on mixing with Reynolds numbers ranging from 1 to 100. The mixing index, which is used as the measurement criteria, is dependent upon Reynolds number and geometrical parameters. RESULTS Through the results of numerical and experimental simulation, it is evident that the arrangement of dislocation sub-channel structure will result in better fluid mixing owing to the combination of the unbalanced inertial collisions, the multidirectional vortices and the collision-induced flow in mixing cavities between every two-looped structure. The effect of transverse Dean Vortices in the vertical plane and expansion vortices in the horizontal plane is beneficial for the increased interfacial area between two species and promoting mixing. The increased width ratio, w3/w4, provided by the dislocation structures, results in better mixing performance, but also causes a higher pressure drop. Experimental results allow better validation of the mixing efficiency of this micromixer. CONCLUSION The best mixing performance was achieved with width ratio of the dislocation sub-channels at w3/w4 = 1.0 and Reynolds numbers less than 80. To consider the mixing effect and the packaging requirements of the experiment, the mixing index of the micromixer with a dislocation sub-channel can reach 86%. © 2013 Society of Chemical Industry

Potential of newly isolated bacterial strains for simultaneous removal of hexavalent chromium and reactive black‐5 azo dye from tannery effluent

Abstract: BACKGROUND Effluents discharged from tannery industry contain significant amount of chromium and synthetic dyes. Both chromium and dyes can be transformed individually into less toxic forms, but very little is known about their simultaneous treatment. The present study was aimed at isolating bacteria capable of removing toxic hexavalent chromium (CrVI) and reactive black-5 azo dye simultaneously in liquid mineral salt medium (MSM). RESULTS About 150 bacterial isolates were collected from tannery wastewater and sludge through enrichment of the MSM with CrVI (2 mg L−1) and reactive black-5 dye (100 mg L−1) under static (batch) condition. Bacterial strains KI (Pseudomonas putida ) and SL14 (Serratia proteamaculans) were able to reduce simultaneously 93% CrVI and 100% color of reactive black-5 azo dye in 24 h at pH 7.2 and 35 °C in a batch culture. Individually, 100% reduction of CrVI and reactive black-5 dye was achieved in 12 h by strain KI and SL14. CONCLUSION These bacterial strains are one of the most efficient bacteria capable of reducing toxic CrVI and synthetic reactive dye simultaneously and could be used for developing bioreactors to treat tannery effluent prior to its discharge into the environment. © 2012 Society of Chemical Industry