Water-soluble polymers are materials rapidly growing in volume and in number of materials and applications. Examples include synthetic plastics such as polyacrylamide, polyacrylic acid, polyethylene glycol, polyethylene oxide and polyvinyl alcohol, with applications ranging from cosmetics and paints to water purification, pharmaceutics and food packaging. Despite their abundance, their environmental concerns (e.g., bioaccumulation, toxicity, and persistence) are still not sufficiently assessed, especially since water soluble plastics are often not biodegradable, due to their chemical structure. This review aims to overview the most important water-soluble and biodegradable polymers, their applications, and their environmental impact. Degradation products from water-insoluble polymers designed for biodegradation can also be water soluble. Most water-soluble plastics are not immediately harmful for humans and the environment, but the degradation products are sometimes more hazardous, e.g. for polyacrylamide. An increased use of water-soluble plastics could also introduce unanticipated environmental hazards. Therefore, excessive use of water-soluble plastics in applications where they can enter the environment should be discouraged. Often the plastics can be omitted or replaced by natural polymers with lower risks. It is recommended to include non-biodegradable water-soluble plastics in regulations for microplastics, to make risk assessments for different water-soluble plastics and to develop labels for flushable materials.

Industrialization is an inevitable part of the progress of civilization. Amid several positive aspects of industrialization, it has a major derogative effect i.e. environmental pollution. Industrial waste water is a major contributor to environmental pollution and hence it needs to be treated to remove harmful contaminants before discharging to the environment. Membrane technology has emerged as one of the most appropriate technologies to treat industrial waste water and in the arena of membranes, nanofiltration membrane is the most advanced one. These are loose RO membranes for which pore size varies between 0.5–5 nm and operating pressure ranges between 5–15 bars. For these charged porous membranes the rejection is governed by both Donnan exclusion and sieving mechanism. These membranes have wide applications in treating effluents from textile, dye, leather, food, pulp and paper and metal industries. NF technology is equally applicable to remove hardness and heavy metals from ground and contaminated water.

Selective separation using efficient high-performance nanofiltration membranes has the potential for widespread application in multiple fields, including dye desalination, industrial wastewater treatment, and resource recovery from different feed streams. This study focused on the design of selective and self-cleaning nanofiltration membranes by incorporating iron aminoclay nanoparticles in a piperazine-based polyamide active layer supported on an ultrafiltration PAN substrate. Fe-AC nanoparticles and thin film nanocomposites (TFNC) were characterized for their morphology, surface chemistry, roughness, and surface area. In terms of wettability/hydrophilicity, TFNC membranes with Fe-AC incorporated had the lowest contact angle of 33.5 degrees, while that of the pristine TFNC0 membrane was 60.5 degrees. They also had a higher surface negative zeta potential and smoother surface morphology. The TFNC membranes also exhibited higher water fluxes and enhanced selectivity towards molecular separation compared to the control membranes. The water flux of the optimized AC polyamide membrane, TFNC3, was 19.70 +/- 0.5 LMH (L. m- 2.h-1), while that of the pristine TFNC0 membrane was 4.85 +/- 0.6 LMH at 4 bar. 98.0-99.0 % rejection of model organic moieties was achieved at a constant flux (Congo red, Eriochrome Black T, methylene blue, Rhodamine 6G, and Crystal violet). When simulated wastewater was purified, the Fe-AC TFNC showed 98.0 % rejection of dyes and 20.0 % rejection of inorganic salts. In long-term filtration studies (>210 h) using simulated wastewater spiked with multiple foulants, >98.0 % rejection of organic matter and foulants was recorded with a stable long-term flux profile. A leaching study confirmed that the membranes were structurally stable, even after the self-cleaning process and at elevated temperatures, without any significant reduction in flux or rejection. Comparing the fouling performance between TFNC3 membranes and commercial reverse osmosis (RO) membranes, the FDR and Flux Recovery Ratio (FRR) values of commercial RO membranes were 58.0 % and 73.0 %, while those of TFNC3 were 47.0 % and 97.0 %, respectively. The results show that the membranes have lower fouling values and higher FRR values when iron clay is present. These results demonstrate the potential of the membranes for effective pre-treatment of various industrial wastewaters and selective separation.

In this study, a biopolymer-based forward osmosis (FO) membrane was used in combination with an easily recoverable and reusable draw solution (DS) for a simultaneous recovery of high-quality water and value-added products from industrial wastewater. Simultaneous wastewater dewatering resulted in a highly concentrated sludge that was reused as the electrode material. In this study, 86.92% dewatering was achieved using an easily recyclable mixture of ethylenediaminetetraacetic acid disodium (EDTA-2Na) with Triton X-100 micelles as the DS and a chitosan membrane with FO. The compatible membrane and the DS showed a flux of 5e6 L m-2 h-1 and a 0.008 +/- 0.002 mol m-2 h-1 reverse solute flux with a retention of >99.0% for all organic pollutants from the chosen real-world wastewater. The recovered DS after the third use showed a >83.57% and >78.84% constant flux retention for deionizedand tannery wastewater as feed. In long-term tests with simulated wastewaters containing various contaminants, they showed >99.0% retention of organics and modern foulants and long-term stability (96 h). At the end of the FO process, sludge with different concentrations of organic wastes was recovered. The recovered solid sludge was carbonized (800 0C) and used as the electrode material in a supercapacitor with a specific capacitance of 165 F/g at a current density of 0.5 A/g.

Environmental and human health are seriously threatened by organic dye pollution. Many efforts have been made to find effective and safe methods of eliminating these contaminants. To mitigate these effects, the hydrothermal method was used to effectively generate a ternary kind of Dy2WO6-ZnO embedded in graphene oxide (DWZG) nanocomposites, which were used to degrade the pollutant. Powder X-ray diffraction (XRD) investigation confirms the crystalline character of the as-prepared DWZG nanocomposite. The Dy2WO6-ZnO composition on the graphene oxide (GO) layer is shaped like a combination of algae (Dy2WO6) and clusters (ZnO), as shown by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) investigation revealed the composition of elements and oxidation state of C, Dy, O, W and Zn elements. Methylene blue (MB) was chosen as the organic dye target for photocatalytic degradation using the produced nanocomposites. MB is degraded with a photocatalytic efficiency of 98.2% in about 30 min using a DWZG catalyst. Based on the result of the research entitled "Reactive Oxidative Species," the primary reactive species involved in the MB degradation are photo-generated (OH)-O-& BULL; and O-2(& BULL;-) radicals. The recycle test was also successful in evaluating the catalysts' long-term viability as well as their reusability.

The use of novel flocculants in combination with a sequencing batch reactor (SBR) for the treatment of landfill leachate and municipal wastewater has been shown to be an effective method for reducing polluted effluents. Co-treatment of landfill leachate with a mixture of municipal wastewater was performed at 5%, 10%, 15% and 20% in SBR and effluent was treated by coagulation-flocculation. SBR with 6 d hydraulic retention time (HRT) and 30 d solids retention time (SRT) removed 58 to 70% COD, 86 to 93% ammonia, 76 to 83% nitrate and 69 to 95% phosphate. Coagulation-flocculation with different dosages of alum and ferric chloride with polyacrylamide grafted gum ghatti (GGI-g-PAM) as a novel flocculant was used for chemical oxygen demand (COD), turbidity, total suspended solids (TSS) and color removal. Maximum COD removal was at 20% leachate, which was 74% with alum at 2800 mg/L and 77% with ferric chloride at 470 mg/L. Alum and ferric chloride with GGI-g-PAM flocculant removed 96% and 82% of turbidity and 80% and 82% TSS, respectively. At 20% leachate, combined treatment with SBR and coagulation-flocculation resulted in the total removal of 89% COD, 83% ammonia, 82% nitrate 98% turbidity and 93% TSS with alum. The combined treatment with ferric chloride resulted in a removal of 90% COD, 86% ammonia, 83% nitrate, 98% turbidity and 94% TSS. Except for nitrate combined treatment with both the coagulants at 20% landfill leachate to municipal wastewater ratio removed COD, ammonia, phosphate and TSS to a level that met international standards for discharges to inland surface water. As such, the use of new flocculants with SBR can help reduce water pollution from landfill leachate and municipal wastewater. In addition to coagulation-flocculation, other physico-chemical processes can also be studied as post-treatment options for the co-treatment of wastewater mixture.

In the present study, HAp-ZnO nanorod nanocomposites were successfully prepared using a customized hydrothermal reactor and studied for their compatibility against MG-63 osteoblast-like cells. The crystallinity, morphology, presence of chemical elements, and surface area properties were studied by XRD (X-ray diffraction), FE-SEM (field emission scanning electron microscopy), TEM (transmission electron microscopy), EDS (energy dispersive spectrum) and N-2 adsorption/desorption isotherm techniques, respectively. Further, the mechanical strength and thermal analysis were carried out using the nanoindentation method and thermogravimetric/differential scanning calorimeter (TG/DSC) methods, respectively. Moreover, in vitro biocompatibility studies for the prepared samples were carried out against human osteosarcoma cell lines (MG-63). The crystalline nature of the samples without any impurity phases was notified from XRD results. The formation of composites with the morphology of nanorods and the presence of desired elements in the intended ratio were verified using FE-SEM and EDS spectra, respectively. The TG/DSC results revealed the improved thermal stability of the HAp matrix, promoted by the reinforcement of the ZnO nanorods. The nanoindentation study ensured a significant enhancement in the mechanical stability of the prepared composite material. Finally, it demonstrated that the HAp matrix's mechanical strength and thermal stability were improved by the reinforcement of ZnO, and the cytotoxicity evaluation affirmed the biocompatible nature of the biomimetic hydroxyapatite in the composite.

Environmental problems caused by plastic pollution are among the most pressing issues of our time. In recent years, metagenomics has become a powerful tool for understanding the microbial communities responsible for plastic biodegradation. In this review, recent developments and trends in metagenomics are discussed, and a comprehensive overview of the metagenomic methodology, analysis, and comparison of plastic-degrading bacteria is provided. In addition, the environmental consequences of plastic degradation are discussed, such as the impact on soil, water, and air quality, as well as the potential health risks posed by ingesting and inhaling microplastics. Possible solutions to the plastic degradation problem, such as using biodegradable materials and implementing recycling programs, are also explained. This review highlights the potential impact of metagenomics on the development of sustainable solutions to plastic pollution.

Photocatalysts workable under direct sunlight are the safe and cost-effective option for water purification. The nanocomposites of strontium oxide and zinc oxide (SZ NCs) were synthesized using coprecipitation method. The respective precursors of SZ NCs were subjected to alkaline hydrolysis and subsequently thermally treated to yield SZ NCs. The SZ NCs with different ZnO composition was synthesized by varying the concentration of ZnO precursor from 0.2 to 1 M. The structural properties of SZ NCs evaluated using X-Ray diffraction (XRD), Thermogravimetric analysis (TGA), and Differential thermal analysis DTA). The optical properties of SZ NCs studied using ultraviolet–visible (UV–Vis) spectroscopic study. The trend observed in the intensity of XRD peaks indicated the occurrence of Zn doping in the crystalline lattice of SrO and the formation of SrO–ZnO composite. Upon incorporation of 1 M of ZnO precursor, the grain size of the SrO was decreased from 49.3 to 27.6 nm. The weight loss in the thermal analysis indicates the removal of carbonates from the sample upon heating and shows the formation of an oxide structure. UV–Vis spectra confirmed that the presence of SrO enhanced the sunlight absorption of SZ NCs. The increase in the composition of ZnO precursors increased the bandgap of SrO (2.09 eV) to the level of ZnO (3.14 eV). SZ NCs exhibited heterostructure morphology, where the nanosized domains with varying shapes (layered and rod-like) were observed. Under direct sunlight conditions, SZ NCs prepared using 1 M/0.6 M of SrO/ZnO precursors exhibited 15–20 % higher photocatalytic efficiency than neat SrO and ZnO. In precise, 1 mg of this SZ NC was degraded 98 % of malachite green dye dissolved in water (10 ppm) under direct sunlight. Additionally, the thermal stability results showed that 18 % decomposition was obtained due to the degradation impurities in SrO/ZnO catalysts and the XRD results revealed that no structural change is obtained in SrO/ZnO photocatalysts after stability test. The SZ NCs can be effectively used as safe and economic sunlight photocatalysts for water purification in remote areas without the electricity.

Diatoms are the most abundant photosynthetic microalgae found in all aquatic habitats. In the extant study, the spent biomass (after lipid extraction) of the centric marine diatom Thalassiosira lundiana CSIRCSMCRI 001 was subjected to acid digestion for the extraction of micro composite inorganic biosilica. Then, the resulting three-dimensional mesoporous biosilica material (diatomite) was used as a filler in polysulfone (PSF) membrane preparation by phase inversion. The fabricated PSF/diatomite composite membranes were characterized by SEM-EDX, TGA, and ATR-IR, and their performances were evaluated. The number of pores and pore size were increased on the membrane surface with increased diatomite in the composite membranes as compared to the control. The diatomite composite membranes had high hydrophilicity and thermal stability, lower surface roughness, and excellent water permeability. Membranes with high % diatomite, i.e., PSF/Dia(0.5), had a maximum water flux of 806.8 LMH (Liter/m(2)/h) at 20 psi operating pressure. High-diatomite content membranes also exhibited the highest rejection of BSA protein (98.5%) and rhodamine 6G (94.8%). Similarly, in biomedical rejection tests, the PSF/Dia(0.5) membrane exhibited a maximum rejection of ampicillin (75.84%) and neomycin (85.88%) at 20 Psi pressure. In conclusion, the mesoporous inorganic biosilica material was extracted from spent biomass of diatom and successfully used in filtration techniques. The results of this study could enhance the application of natural biogenic porous silica materials in wastewater treatment for water recycling.