Sivaraman Prabhakar

Bio: Sivaraman Prabhakar is an academic researcher from SRM University. The author has contributed to research in topics: Reverse osmosis & Desalination. The author has an hindex of 13, co-authored 53 publications receiving 486 citations. Previous affiliations of Sivaraman Prabhakar include Bhabha Atomic Research Centre.

Extraction of uranium from the concentrated brine rejected by integrated nuclear desalination plants

Abstract: This work was carried out under the specific collaboration agreement between the Bhabha Atomic Research Centre (BARC) from India and the Commissariat a l'Energie Atomique (CEA) from France. This paper summarises first results of review and research on the possible extraction of uranium from the concentrated brine rejected by integrated nuclear desalination systems, which both partners are currently developing in the two organisations. Three innovative and efficient methods of uranium extraction have been proposed: 1) Resin grafted with calixarene: this method has the advantage of very high selectivity. Its performances, especially for large-scale extraction, still need further RD 2) Magnetic separations: yet another method with high selectivity, easy separation and affording high degree of material recovery. The method, however, is in developmental stage; 3) Canal system with Braid adsorbents: high selectivity. Appears to be feasible in conjunction with existing technology. It would nonetheless require large amounts of adsorbents and adequate infrastructure.

Removal and recovery of heavy metals through size enhanced ultrafiltration using chitosan derivatives and optimization with response surface modeling.

Abstract: N‑N‑N‑triethylammonium chitosan (TEAC) and carboxymethyl chitosan (CMCh), the two water-soluble chitosan derivatives were utilized for the removal and recovery of heavy metals by size enhanced ultrafiltration (SEUF). The strong positive quaternary ammonium [–N+(C2H5)3] cation in TEAC interacts with Cr(VI), which exists as a strong chromate anion thereby enabling the efficient removal of chromate through ultrafiltration. CMCh consists of COOH and NH2 moieties, which facilitate interactions with heavy metals such as Cu(II) and Ni(II). FTIR, SEM, and EDAX were used to characterize the chitosan derivatives before and after the removal of metals. The experiments were designed with the central composite design (CCD) of response surface methodology (RSM). The metal ion removal experiments were conducted as per the statistical design to determine the optimum process conditions; initial pH of the feed solution, polymer to metal loading ratio (P/M), and initial concentration of the feed solution. The optimization study was conducted to maximize the heavy metal rejection and binding capacity of the chitosan derivatives. The analysis of variance (ANOVA) was performed to validate the developed regression models.

Valorization of food waste as adsorbents for toxic dye removal from contaminated waters: A review.

Abstract: Industrial contaminants such as dyes and intermediates are released into water bodies, making the water unfit for human use. At the same time large amounts of food wastes accumulate near the work places, residential complexes etc. polluting the air due to putrefaction. The need of the hour lies in finding innovative solutions for dye removal from wastewater streams. In this context, the article emphasizes adoption or conversion of food waste materials, an ecological nuisance, as adsorbents for the removal of dyes from wastewaters. Adsorption, being a well-established technique, the review critically examines the specific potential of food waste constituents as dye adsorbents. The efficacy of food waste-based adsorbents is examined, besides addressing the possible adsorption mechanisms and the factors affecting phenomenon such as pH, temperature, contact time, adsorbent dosage, particle size, and ionic strength. Integration of information and communication technology approaches with adsorption isotherms and kinetic models are emphasized to bring out their role in improving overall modeling performance. Additionally, the reusability of adsorbents has been highlighted for effective substrate utilization. The review makes an attempt to stress the valorization of food waste materials to remove dyes from contaminated waters thereby ensuring long-term sustainability.

Conversion of food waste to energy: A focus on sustainability and life cycle assessment

Abstract: Rapid industrialization and population growth have resulted in the wastage of significant quantity of food globally throughout the value chain right from harvesting to storage, processing and consumption. Normally, these waste materials are allowed to decay in the natural process or burnt to recover a part of the energy in the thermal form, leading to environmental pollution and loss of value. There is an imperative need to realize that food waste is a bundle of energy, which requires carefully planned recovery without damaging the environment. Conversion of food waste to bio-based liquid or gaseous fuels appears to be an attractive option to meet the escalating demand for fuel and at the same time slowing down the fast-depleting fossil fuel resources. In this context, it is felt appropriate to review the current status of the available technologies which are used in the disposal of food waste in order to identify the variables for process intensification to convert them to fuel keeping in mind the environmental concerns and logistics of utilization. The technologies including incineration, landfill, composting, anaerobic digestion, pyrolysis and biochemical methods have been assessed alongside the recent developing technologies such as hydrothermal carbonization and supercritical water gasification. The critical evaluations of these technologies have been made based on the concepts of life cycle analysis, multi-objective optimization and circular bio-economics which help in assessing the environmental impact. Finally, safety aspects and the way forward are highlighted for future work. This article could form a promising path towards a holistic assessment of efficient food waste to energy conversion for a sustainable development.

Extraction and detection methods of microplastics in food and marine systems: A critical review

Abstract: The ubiquitous presence of microplastics as contaminants in the ecosystem has become a matter of environmental concern gaining considerable attention in the research community as well as public arena. Lack of efficient collection and improper management of plastic have resulted in the enormous amounts of plastic wastes landing into the marine systems with oceans being the ultimate sink. Due to non-biodegradability, these plastics break down into smaller fragments over a period of time leading to consumption by aquatic species, threatening marine life. In the recent years, a wide range of food products has also been contaminated with microplastics directly affecting human health. This review focuses on the separation and identification technologies for extraction and detection of microplastics in food and marine ecosystems. Efficient technologies like floatation, membrane separation, chemical treatment, enzymatic treatment, and other miscellaneous techniques have been discussed considering their merits and demerits. Additionally, identification technologies like optical detection, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, thermo-analytical methods, and hyperspectral imaging have been emphasized for the detection of microplastic particles. The emerging techniques like enzymatic digestion combined with hyperspectral imaging could be a possible way for obtaining higher separation efficiency and characterization with minimal harm to food sample. This article narrows the gap for choosing a standard separation technology for microplastic detection in food matrices keeping in mind the composition, particle size, shape, data visualization techniques and cost.

Reverse osmosis desalination: Water sources, technology, and today's challenges

Abstract: Reverse osmosis membrane technology has developed over the past 40 years to a 44% share in world desalting production capacity, and an 80% share in the total number of desalination plants installed worldwide. The use of membrane desalination has increased as materials have improved and costs have decreased. Today, reverse osmosis membranes are the leading technology for new desalination installations, and they are applied to a variety of salt water resources using tailored pretreatment and membrane system design. Two distinct branches of reverse osmosis desalination have emerged: seawater reverse osmosis and brackish water reverse osmosis. Differences between the two water sources, including foulants, salinity, waste brine (concentrate) disposal options, and plant location, have created significant differences in process development, implementation, and key technical problems. Pretreatment options are similar for both types of reverse osmosis and depend on the specific components of the water source. Both brackish water and seawater reverse osmosis (RO) will continue to be used worldwide; new technology in energy recovery and renewable energy, as well as innovative plant design, will allow greater use of desalination for inland and rural communities, while providing more affordable water for large coastal cities. A wide variety of research and general information on RO desalination is available; however, a direct comparison of seawater and brackish water RO systems is necessary to highlight similarities and differences in process development. This article brings to light key parameters of an RO process and process modifications due to feed water characteristics.

Polymer-matrix nanocomposite membranes for water treatment

Abstract: One of the grand challenges to sustain the modern society is to secure adequate water resources of desirable quality for various designated uses. To address this challenge, membrane water treatment is expected to play an increasingly important role in areas such as drinking water treatment, brackish and seawater desalination, and wastewater treatment and reuse. Existing membranes for water treatment, typically polymeric in nature, are still restricted by several challenges including the trade-off relationship between permeability and selectivity (also called Robeson upper boundary in membrane gas separation), and low resistance to fouling. Nanocomposite membranes, a new class of membranes fabricated by combining polymeric materials with nanomaterials, are emerging as a promising solution to these challenges. The advanced nanocomposite membranes could be designed to meet specific water treatment applications by tuning their structure and physicochemical properties (e.g. hydrophilicity, porosity, charge density, and thermal and mechanical stability) and introducing unique functionalities (e.g. antibacterial, photocatalytic or adsorptive capabilities). This review is to summarize the recent scientific and technological advances in the development of nanocomposite membranes for water treatment. The nanocomposite membranes were classified into (1) conventional nanocomposite, (2) thin-film nanocomposite (TFN), (3) thin-film composite (TFC) with nanocomposite substrate, and (4) surface located nanocomposite, based on the membrane structure and location of nanomaterial. Challenges and future research directions in developing high performance nanocomposite membranes were also discussed.

Carbon nanotube membranes for water purification: A bright future in water desalination

Abstract: Water pollutants have huge impacts on the entire living systems including terrestrial, aquatic, and aerial flora and fauna. In addition to conventional priority, and newly emerging micro/nano-pollutants, increasing global warming and consequent climate changes are posing major threats to the fresh water availability. Global warming and climate change are constantly increasing the salinity level of both land and sea water, dwindling the availability of existing fresh water for household, agriculture and industry. This has made it urgent to invent an appropriate water treatment technology that not only removes macro-, micro- and nano-pollutants but also desalinates water to a significant extent. Tip-functionalized nonpolar interior home of carbon nanotubes (CNTs) provides strong invitation to polar water molecules and rejects salts and pollutants. Low energy consumption, antifouling and self-cleaning functions have made CNT membranes extraordinary over the conventional ones. We comprehensively reviewed here molecular modeling and experimental aspects of CNT-membrane fabrication and functionalization for the desalination of both sea and brackish water. We present here the current problems and future challenges in water treatments. The article is potentially important for the hydrologists, membrane technologists, environmentalists and industrialists working in the field of water purification technologies to eradicate fresh water crisis in near future.

Application of carbon nanotube technology for removal of contaminants in drinking water: a review.

Abstract: Carbon nanotube (CNT) adsorption technology has the potential to support point of use (POU) based treatment approach for removal of bacterial pathogens, natural organic matter (NOM), and cyanobacterial toxins from water systems. Unlike many microporous adsorbents, CNTs possess fibrous shape with high aspect ratio, large accessible external surface area, and well developed mesopores, all contribute to the superior removal capacities of these macromolecular biomolecules and microorganisms. This article provides a comprehensive review on application of CNTs as adsorbent media to concentrate and remove pathogens, NOM, and cyanobacterial (microcystin derivatives) toxins from water systems. The paper also surveys on consideration of CNT based adsorption filters for removal of these contaminants from cost, operational and safety standpoint. Based on the studied literature it appears that POU based CNT technology looks promising, that can possibly avoid difficulties of treating biological contaminants in conventional water treatment plants, and thereby remove the burden of maintaining the biostability of treated water in the distribution systems.