Showing papers by "Volker Hessel published in 2023"

Process Technology and Sustainability Assessment of Wastewater Treatment

Abstract: Removal of heavy metals in wastewater treatment is crucial to protect the environment, wildlife, and human health. Various techniques have been developed focusing on removal of heavy metal ions, pharmaceuticals, and other contaminants from different wastewater sources. The main methods include adsorption, filtration, ion exchange, electrochemical, reverse osmosis, precipitation, flotation/coagulation/flocculation, and photocatalytic-based treatments. This paper comprehensively assesses the sustainability of those common technologies used for wastewater process treatment. The sustainability profile depends mostly on the exact approach followed for each technology, including its energy consumption, type of radiation (where appropriate), auxiliary materials used (e.g., catalysts, adsorbents), and further specific experimental process settings. Thus, while sustainability inevitably provides a multifaceted answer, the review finally aims for sustainability benchmarking of all technologies, by compressing the manifold outcomes toward a compact information set, such as a table and radar plot.

Sensor to Electronics Applications of Graphene Oxide through AZO Grafting

Abstract: Graphene is a two-dimensional (2D) material with a single atomic crystal structure of carbon that has the potential to create next-generation devices for photonic, optoelectronic, thermoelectric, sensing, wearable electronics, etc., owing to its excellent electron mobility, large surface-to-volume ratio, adjustable optics, and high mechanical strength. In contrast, owing to their light-induced conformations, fast response, photochemical stability, and surface-relief structures, azobenzene (AZO) polymers have been used as temperature sensors and photo-switchable molecules and are recognized as excellent candidates for a new generation of light-controllable molecular electronics. They can withstand trans-cis isomerization by conducting light irradiation or heating but have poor photon lifetime and energy density and are prone to agglomeration even at mild doping levels, reducing their optical sensitivity. Graphene derivatives, including graphene oxide (GO) and reduced graphene oxide (RGO), are an excellent platform that, combined with AZO-based polymers, could generate a new type of hybrid structure with interesting properties of ordered molecules. AZO derivatives may modify the energy density, optical responsiveness, and photon storage capacity, potentially preventing aggregation and strengthening the AZO complexes. They are potential candidates for sensors, photocatalysts, photodetectors, photocurrent switching, and other optical applications. This review aimed to provide an overview of the recent progress in graphene-related 2D materials (Gr2MS) and AZO polymer AZO-GO/RGO hybrid structures and their synthesis and applications. The review concludes with remarks based on the findings of this study.

Microfluidic Spontaneous Emulsification for Generation of O/W Nanoemulsions - Opportunity for In-Space Manufacturing.

Abstract: The use of microfluidics for oil-in-water (O/W) nanoemulsification via spontaneous self-assembly is demonstrated. As this is known to be a longish process, both single- and multi-contact microfluidic reactors were tested, the latter providing a longsome, constant microfluidic treatment to maintain advanced phase and interfacial mass transfer. Microfluidic devices provided strong advantages above conventional systems for spontaneous emulsification, with droplet sizes of 62 nm at desired surfactant-to-oil ratios (SOR) and a decrease of 90% in process time. Multi-contact microfluidics have better performance than their single-contact counterparts, while critical aspects, e.g., process robustness, are also discussed. Ternary phase diagram analysis of the three components (oil, water, surfactant) allowed to decide for the right mixing ratio and sequence of mixing steps for the nanoemulsions. Microfluidic spontaneous emulsification met objective functions of the intended application to provide fortified beverages to astronauts in space exploration. In that viewpoint, an advantage was to achieve stable nanoemulsions at a level of concentrations much higher as compared to application (human intake), allowing a dilution factor to the final product of up to 100. This decreases notably the process time and allows for process flexibility, e.g., to dilute or tailor Earth-prepared nanoemulsion concentrate payloads in space. This article is protected by copyright. All rights reserved.

Microfluidic steam-based synthesis of luminescent carbon quantum dots as sensing probes for nitrite detection

Abstract: Abstract In this work, an efficient and green approach has been presented to prepare carbon quantum dots (CQDs) from watermelon juice through a microfluidic steam-based method, with a view to enabling continuous production at scale, i.e., to save time, costs, or energy as compared to conventional production using an autoclave. The evolution of the product formation through multifarious intermediates generated in different stages of the reaction process was characterized. Computational fluid dynamics simulations reveal the pressure and velocity profiles in the microchannel to exert process control. These determine the quality of the obtained CQDs by influencing the particle size transformations and manifold chemicals along the microchannel axis. The optimal reaction conditions and reaction mechanism for the synthesis of CQDs were investigated. Additionally, the synthesized CQDs demonstrated good fluorescence properties as well as a specific response to NO 2 − {\text{NO}}_{2}^{-} in both fluorescence and spectrophotometric modes, providing great potential for their application in environmental monitoring.

Growth response of Bacillus coagulans on TiO2 nanoparticles by RNA-Seq analysis of the customary probiotic strain

Abstract: The phosphoenolpyruvate sugar phosphotransferase systems in bacteria are complex enzyme systems carrying out various important functions like detection, phosphorylation and transport of several sugar substrates including mono and disaccharides, amino sugars, etc. This key enzyme complex prevents the efflux of sugar substrates by phosphorylation and prepares them for energy production and metabolism. In this study, a high throughput RNA sequencing method was used to compare the gene expression in Bacillus coagulans treated with nano titanium dioxide (TiO2) rutile. Out of 3,175 genes, 499 were differentially expressed. Gene Ontology analysis revealed 239 significant genes. In the biological process category, we found the phosphoenolpyruvate-dependent sugar phosphotransferase systems are the dominant ones and are involved in the uptake of specific carbohydrate sources. In our previous study, we showed increased growth of bacteria in presence of nano TiO2 anatase with a sharp rise in ATP concentrations. We know that, among metal oxide-based nanoparticles, TiO2 is placed at the topmost position in the agri-food sector based on its use and their reactivity with human beneficial gut flora, commonly known as probiotics, becoming a major concern. Hence, the interaction of TiO2 rutile nanoparticles on Bacillus coagulans was studied thoroughly at the transcriptomics level; with depth.

The Kinetics of the Redox Reaction of Platinum(IV) Ions with Ascorbic Acid in the Presence of Oxygen

Abstract: In this work, the kinetics of the redox reaction between platinum(IV) chloride complex ions and ascorbic acid is studied. The reduction process of Pt(IV) to Pt(II) ions was carried out at different reagent concentrations and environmental conditions, i.e., pH (2.2–5.1), temperature (20–40 °C), ionic strength (I = 0.00–0.40 M) and concentrations of chloride ions (0.00–0.40 M). The kinetic traces during the reduction process were registered using stopped-flow spectrophotometry. Based on the kinetic traces, the rate constants were determined, and the kinetic equations were proposed. It was shown that in the mild acidic medium (pH = 2.5), the reduction process of Pt(IV) to Pt(II) ions is more complex in the presence of oxygen dissolved in the aqueous solutions. For these processes, the values of the enthalpy and entropy of activation were determined. Moreover, the mechanism of the reduction of Pt(IV) to Pt(II) ions was proposed. The presented results give an overview of the process of the synthesis of platinum nanoparticles in the solution containing oxygen, in which the reduction process of Pt(IV) to Pt(II) ions is the first step.

Plasma Regeneration of Spent Pd/Al2O3 Catalysts and Their Electrochemical Performance

Abstract: A dielectric barrier discharge (DBD) plasma was applied to reactivate palladium on alumina (Pd/Al2O3) waste catalysts at extreme conditions, addressing a common problem of reusing the spent catalysts instead of discarding them. Experimental studies of the effect of gas composition in the plasma process reveal different extent of coke elimination and different electrochemical performance of the reactivated Pd/Al2O3 catalysts, ranked as Ar-treated > N2-treated > O2-treated > untreated spent catalyst at fixed gas flow rate and regeneration time. The effect of the regeneration time and gas flow rate on the electrochemical performance of the reactivated Pd/Al2O3 catalysts was systematically studied. The results show that for Ar and N2 process gas, the electrochemical performance of the plasma-treated spent catalyst is improved with the increase of the gas flow rate and the treatment time. However, if O2 is used, then the electrochemical performance of the spent catalyst decreases with the increase of the gas flow rate and the treatment time. The XPS results show that higher oxidation degrees of Pd reduces the electrochemical performance. This study demonstrates a new strategy for reusing the otherwise waste catalyst in a simple and environment-benign solvent-free manner.

Evolution paths from gray to turquoise hydrogen via catalytic steam methane reforming: Current challenges and future developments

Abstract: Fossil fuel depletion, global warming, climate change, and steep hikes in the price of fuel are driving scientists to investigate commercial and environmentally friendly energy carriers like hydrogen. Steam methane reforming (SMR), a current commercial route for H2 production, has been considered the best remedy to fulfill the requirements. Despite the remarkable quantity of H2 produced by the SMR, this technology still faces major challenges such as catalyst deactivation due to the sintering of metal nanoparticles, coking, and generation of a large quantity of CO2. Firstly, the effects of catalyst types, kinetic models, and operating conditions on high-yield H2 production, the evolution path from gray to blue, via the conventional SMR are comprehensively reviewed. Secondly, exploiting intensified techniques such as membrane technology, sorption, fluidization, and chemical looping for SMR to blue H2 are discussed in detail. Further, a novel and sustainable path for the SMR process, hybridizing the use of novel materials and emerging technologies to produce turquoise H2, is proposed. Finally, the critical points for steam reforming process technology that can help leverage environmental, social, and governance (ESG) profiling have been discussed.

Synthesis of CaCO 3 /Cu 2 O/GO Nanocomposite Catalysts for Hydrogen Production from NaBH 4 Methanolysis

Abstract: : The synthesis of CaCO 3 /Cu 2 O/GO nanocomposites was developed by sol-gel auto-combustion method. The analysis of structure was completed on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and environmental scanning electron microscopy (ESEM). The XRD spectra of the nanocomposites matched the crystal structure of CaCO 3 /Cu 2 O. The average crystal size was 20 nm for Cu 2 O and 25 nm for CaCO 3 nanoparticles. FTIR data showed the absorption bands of Cu 2 O and GO. Raman spectroscopy data confirmed the formation of GO sheets. ESEM micrographs displayed spherical nanoparticles dispersed in GO sheets. X-ray photoelectron spectroscopy showed the peaks of Cu 2p, O 1s, C 1s, Cu 3s, and Ca 2p. The spectra of optical absorption revealed an absorption band of around 450 nm. The calcium content increase led to a decrease in the optical energy gap from 2.14 to 1.5 eV. The production of hydrogen from NaBH 4 across the methanolysis reaction was accelerated by the CaCO 3 /Cu 2 O/GO nanocomposites. Therefore, these nanocomposites are superior in catalytic hydrogen production systems.

The Mechanism of Phase Transfer Synthesis of Silver Nanoparticles Using a Fatty Amine as Extractant/Phase Transfer Agent

Abstract: The paper presents the research results on synthesizing silver nanoparticles in aqueous solutions and their extraction into the organic phase. Studies have shown that it is best to perform the extraction process using n-hexane > cyclohexane > toluene > chloroform > ethyl acetate. The results show a correlation between the dielectric constant of the organic phase and its ability to extract nanoparticles. The lower the dielectric constant is, the higher the extractability. The hydrodynamic radius of the silver nanoparticles changes after transfer to the organic phase, depending greatly on the organic phase used. The extraction mechanism is complex and multi-step. As the first step, the Ag nanoparticles are transferred to the phase boundary. As the second step, the octadecylamine (ODA) molecules adsorb on the silver nanoparticles (AgNPs) surface. The change in particle shape was also noted. This suggests that the interfacial processes are more complex than previously reported. Below the initial concentration of ODA 2 × 10−4 M, the formation of a third phase has been observed. In a one-stage experiment, the concentration of silver nanoparticles after transferring to the organic phase was increased 500 times in about 10 s. The role of the concentration of ODA, therefore, is not only a measure of the extraction efficiency and productivity but functions as an enabler to maintain favorable biphasic processing, which underlines the role of the solvent again.

Internalisation of environmental costs of decentralised nitrogen fertilisers production

Abstract: Ammonia (NH3) production is an energy-intensive process that is concentrated in a few countries at large-scale plants, mainly using the Haber-Bosch (HB) process. Local plants next to farmers can reduce environmental impacts, as well as reduce storage, shortage risks, and price volatility of fertilisers. Since local NH3 production is not cost-effective, we analyse how internalisation of environmental impacts into economic analyses could help to promote novel technologies for NH3 synthesis when supplied with renewable energy.Mini-HB plants working at high pressure and temperature, as well as novel alternatives based on plasma reactors working at ambient conditions and using electricity from renewable sources, have been recently proposed for decentralised NH3 production. To evaluate the environmental performances of these alternative and traditional NH3 pathways, a life cycle assessment was performed to quantify the reduced emissions in each production process and the impacts of by-product utilisation, such as steam, oxygen, or carbon black. Different scales of storage and transportation, fuelled by traditional energy sources, were modelled to quantify the impacts of the simplified NH3 supply chains. A review of monetary valuation coefficients was performed to internalise the life cycle environmental impacts into the techno-economic analyses of NH3 production in Australia.Most of the estimated environmental costs were due to the carbon emissions of conventional plants and thermal plasma plants because of the use of fossil-based electricity. However, the high external costs associated with the photochemical oxidant formation and particulate matter affected the thermal plasma and non-thermal plasma (NTP) plants, costing in total 9,500 and 4,200 $/t NH3, respectively, due to the impacts of solar panels manufacturing. In contrast, electrolyser-HB plants obtained rates of 114 $/t NH3 because of the high energy efficiency and oxygen sales. In the future scenario for NTP-based plants, this alternative could also be competitive with rates of 222 $/t NH3. Additionally, the estimated total external costs for the conventional NH3 industry in Australia amounted to about US$5 billion per year.Electrolyser-HB plants could be cost-effective in the short term due to the energy efficiency of HB processes. However, the HB process has reached its efficiency limits, while the NTP process still has room for improvement, as well as its production costs are lower at smaller scales. In addition, if monetised environmental costs are analysed for a whole industry, public administrations could be prompted to invest the expected savings in the promotion of these novel technologies.The online version contains supplementary material available at 10.1007/s11367-023-02187-5.

Purification of Halon 1301 using industrial-scale heat-pump-assisted batch distillation: simulation and experiment

Abstract: In this study, the purification of Halon 1301 from an industrial waste gas mixture using an existing heat-pump-assisted batch distillation system was investigated. A cold water circuit and a hot water circuit are added to the conventional vapor compression heat pump for easy operation. To design and optimize the separation, where several design variables and constraints must be verified and satisfied, a modification of the design methodology proposed by Long et al. [1] was used. Following design using Aspen Hysys software in the simulation of the shortcut column and heat pump system and Aspen Batch Modeler in the simulation of batch distillation, experimental operation of the existing heat-pump-assisted batch distillation system was performed to purify Halon 1301. The experimental performance matched well with that in the simulation. The purification of Halon 1301 with purity of 99.9% was accomplished after 22 h under the designed and optimized operating conditions. The results show that the reboiler duty and operating costs of the existing industrial system can be saved by as much as 100.0% and 36.5%, respectively, compared with a conventional batch distillation column. In addition, the total CO 2 emission was reduced by as much as 43.7% compared with that of the conventional process. Moreover, the proposed design is convenient and gives reliable performance. This study demonstrated that the use of an advanced distillation configuration in industrial applications is practically viable and economical.