Abstract Over 80% of wastewater worldwide is released into the environment without proper treatment. Whilst environmental pollution continues to intensify due to the increase in the number of polluting industries, conventional techniques employed to clean the environment are poorly effective and are expensive. MXenes are a new class of 2D materials that have received a lot of attention for an extensive range of applications due to their tuneable interlayer spacing and tailorable surface chemistry. Several MXene‐based nanomaterials with remarkable properties have been proposed, synthesized, and used in environmental remediation applications. In this work, a comprehensive review of the state‐of‐the‐art research progress on the promising potential of surface functionalized MXenes as photocatalysts, adsorbents, and membranes for wastewater treatment is presented. The sources, composition, and effects of wastewater on human health and the environment are displayed. Furthermore, the synthesis, surface functionalization, and characterization techniques of merit used in the study of MXenes are discussed, detailing the effects of a range of factors (e.g., PH, temperature, precursor, etc.) on the synthesis, surface functionalization, and performance of the resulting MXenes. Finally, the limits of MXenes and MXene‐based materials as well as their potential future research directions, especially for wastewater treatment applications are highlighted.
Abstract The biosorption of Pb(II) ions from aqueous solution has been studied using both the intact and thermolyzed cells of Pseudomonas aeruginosa. Further, the role of the major cell wall components, namely DNA, protein, polysaccharide, and lipid, in Pb(II) binding has been assessed using an enzymatic treatment method. The Pb(II) bioremediation capability of P. aeruginosa cells has been investigated by varying the parameters of pH, time of interaction, amount of biomass, and concentration of Pb(II). The complete bioremoval of Pb(II) using intact cells has been achieved for an initial Pb(II) concentration of 12.4 mg L−1 at pH 6.2 and temperature 29 ± 1 °C. The biosorption isotherm follows Langmuirian behavior with a Gibbs free energy of −30.7 kJ mol−1, indicative of chemisorption. The biosorption kinetics is consistent with a pseudo-second-order model. The possible Pb(II) binding mechanisms of P. aeruginosa cells are discussed based on characterization using zeta potential measurements, Fourier transform infra-red spectroscopy, and energy dispersive X-ray spectroscopy. The results confirm that among the major cell wall components studied, polysaccharide shows the highest contribution towards Pb(II) binding, followed by DNA, lipid, and protein. Similar studies using thermolyzed cells show higher Pb(II) uptake compared to the intact cells both before and after enzymatic treatment.
Industrialization, urbanization and technological developments have improved the standard of living for humans on the one hand, but they also have resulted in the generation of wastes containing toxic heavy metals that are detrimental to the ecosystem on the other hand. Therefore, the treatment of waste water containing toxic heavy metals before discharging into the environment has become imperative. Though, the conventional waste water treatment methods like adsorption, electrochemical process, ion-exchange, precipitation, solvent extraction, etc. have served the purpose of removing toxic heavy metals, they have certain limitations such as formation of secondary sludge, inefficiency in removing lower metal concentration, high cost, to name a few. Thus, it becomes of interest to explore alternative cost effective methods capable of removing lower concentrations of heavy metals from waste water.
The method of bioremediation which uses microorganisms for toxic heavy metal removal has gained significance. Various combinations of microorganisms and heavy metals have been researched to assess the abilities of the selected microorganisms in removing the considered metals. Majority of the research studies have focused on the biosorption of metals by the whole cells. However, there is a paucity of research on the role played by the individual cell wall components in metal removal. In addition to remediation, the detection of heavy metals in waste waters is also of equal importance.
In the present research study, the significance of bacteria of Pseudomonas species namely P. putida, P. aeruginosa and P. fluorescens for lead remediation have been assessed. Further, detailed studies have been carried out to elucidate the mechanisms of lead removal through the assessment of the roles played by the individual cell wall components. The lead removal capacities of the individual EPS components purified from the Pseudomonas sp. have been determined. Various strategies have been adopted to enhance the lead removal capacities of the three Pseudomonas sp. by thermolysis. For the biosorption studies, the parameters namely pH, time of contact, biomass loading and lead concentration have been optimized to obtain the maximum lead binding. Apart from lead removal, biologically modified carbon paste electrodes (CPEs) have been developed using the Pseudomonas sp. cells and their EPS components.
The major objectives of this research work are enumerated as follows:
1. Study of the bioremediation of lead from aqueous solutions using cells of P. putida, P. aeruginosa and P. fluorescens.
2. Understanding the role of bacterial cell wall and its components in lead uptake.
3. Effect of thermolysis of the chosen bacterial cells on lead uptake
4. Determination of the lead uptake capacity of extracellular polymeric substances (EPS) of the selected Pseudomonas sp. namely, proteins, polysaccharides, biosurfactants and DNA.
5. Enrichment of lead binding proteins from total bacterial protein and examination of the lead binding capacity…
The number of possible application of microbial xylanase in the pulp and paper industry is gradually increasing and several are approaching commercial use. Xylanase are hydrolytic enzymes, which randomly cleave the β-1-4 backbone of the complex plant cell wall polysaccharide xylan.
Graphite is an integral part of lithium-ion batteries (LIBs). However, due to limited resources and high production cost of the highly purified (battery grade) graphite are becoming a challenge to meet the ever-increasing demands for energy storage devices. One viable approach is to recycle the spent graphite anodes from end-of-life LIBs. Importantly, recycling of spent lithium-ion batteries (LIBs) is off utmost importance to address the global challenge of electronic waste management. Herein, we present an environment friendly technique of graphite recycling from the spent LIB by water leaching, followed by atmospheric plasma jet printing. The major advantage of this method is that it does not require any binders or conductive diluents. Plasma printed recycled graphite showed significantly enhanced specific capacity of 402 mAh g -1 at 500 mA g -1 at the end of the 1000 th charge-discharge cycles, in comparison to with water-washed recycled graphite (112 mAh g -1 ) and an 23.35 times faster diffusivity of Li + . A detailed experimental investigation revealed the plasma activation of the graphitic structure resulted in the improved reversible Li + storage. This work provides a new perspective on the recycling strategy of graphite anodes using the in-situ plasma functionalization strategy, a significant step towards the sustainable future of LIBs.
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