An overview on the key advantages and limitations of batch and dynamic modes of biosorption of metal ions

Water purification using adsorption is a crucial process for maintaining human life and preserving the environment. Batch and dynamic adsorption modes are two types of water purification processes that are commonly used in various countries due to their simplicity and feasibility on an industrial scale. However, it is important to understand the advantages and limitations of these two adsorption modes in industrial applications. Also, the possibility of using batch mode in industrial scale was scrutinized, along with the necessity of using dynamic mode in such applications. In addition, the reasons for the necessity of performing batch adsorption studies before starting the treatment on an industrial scale were mentioned and discussed. In fact, this review article attempts to throw light on these subjects by comparing the biosorption efficiency of some metals on utilized biosorbents, using both batch and fixed-bed (column) adsorption modes. The comparison is based on the effectiveness of the two processes and the mechanisms involved in the treatment. Parameters such as biosorption capacity, percentage removal, and isotherm models for both batch and column (fixed bed) studies are compared. The article also explains thermodynamic and kinetic models for batch adsorption and discusses breakthrough evaluations in adsorptive column systems. The review highlights the benefits of using convenient batch-wise biosorption in lab-scale studies and the key advantages of column biosorption in industrial applications.

Multifaceted Anticancer Potential of Gnidia glauca (Fresen.) Gilg Leaf Alkaloids: Impact on Multiple Cellular Targets

Gnidia glauca (Fresen.) Gilg has demonstrated significant anticancer potential through multiple mechanisms, including apoptosis induction, as shown by the TUNEL assay against MCF-7 cells, modulation of tubulin polymerization, preservation of mitochondrial function indicated by the JC-1 assay, and inhibition of DNA polymerase α and β activities. Rationale for the present study is to investigate the potential anticancer properties of G. glauca leaf alkaloid extract. Fresh and healthy G. glauca leaves were cleaned, shade-dried, and the powder was defatted, extracted with 10% acetic acid in ethanol, and subjected for alkaloid extraction. The partially purified G. glauca leaf alkaloid extract was evaluated for its effects on tubulin polymerization, DNA polymerase activity, mitochondrial membrane potential, and apoptosis studies using human breast cancer (MCF-7) cells by flow cytometry. The extract was found to affect microtubule assembly in a concentration-dependent manner (15.125-250 μg/mL), indicating presence of alkaloids that function as spindle poison agents. Leaf alkaloid extract of G. glauca was also found to affect the mitochondrial membrane potential with IC50 value 144.51 μg/mL, and inhibited DNA polymerase α and β activities dose dependently, thus potentially interfering with DNA replication and repair processes. Leaf alkaloid extract also showed the potential to induce DNA damage of 53.6%, albeit somewhat less than the standard drug camptothecin (64.94%) as confirmed by the TUNEL assay. Additionally, the GgLAE (IC50 144.51 μg/mL) showed significant inhibition of MCF-7 cells proliferation after 24 h, revealing phase arrests in sub G0/G1, S, and G2/M. These findings suggest that G. glauca leaf alkaloid extract contains alkaloids that possess anticancer properties with multiple targets, making the plant a natural source for a promising phytochemical drug candidates for further evaluation in pre-clinical and clinical studies. Further investigations are warranted to determine the efficacy, safety, identification and characterization of the alkaloids, and evaluate and determine their potential applications in cancer therapy.

Health risks assessment and source admeasurement of potentially dangerous heavy metals (Cu, Fe, and Ni) in rapidly growing urban settlement

Environmental contamination is a global challenge that impacts every aspect of ecosystem. The contaminants from anthropogenic or industrial trash continually recirculate into the environment, agricultural land, plants, livestock, and ultimately into humans by way of the food chain. After an increase in human and farmland animal deaths from illnesses due to contaminated drinking water, toxic metal water poisoning has remained a global concern. Diverse environmental and enforcement organisations have attempted to regulate the activities that serve as precursors to these heavy metals which have been proven ineffective. These unnecessary metals have severely hampered most biological processes. The presence of hazardous metals, which are harmful at extremely high levels and have a negative effect on the health of living bodies generally degrades the nutritional value of water. In order to evaluate the heavy metals (Cu, Ni, and Fe) toxicity of groundwater in pri-urban areas, the current study was conducted that have been considered as advance solution to tackle climate change which influence coastal ecosystem. Additionally, the impacts of soil and plant (spinach and brassica) contamination from groundwater were evaluated. The heavy metals were examined in the soil and groundwater samples (Pb, Fe and Ni). While Fe concentrations in water samples were found to be high as 1.978 mg/L as compared to Ni and Cu values low. According to WHO guidelines, the mean value of Fe exceeds the limit value. Similarly, Cu had a higher mean value (0.7 mg/L) in soil samples than other metals (Ni and Fe). In comparison to Ni and Cu, the Fe concentrations in spinach and brassica plants samples are greater, at 17.2 mg/L and 3.22 mg/L, respectively. The possible effects of metal poisoning of groundwater and plants on human health have been assessed using the Hazard Quotient (HQ), Evaluated Daily Intake (EDI), and Incremental Life Time Cancer Risk formulas (ILTCR). When drinking Ni-contaminated water, humans are more at risk of developing cancer (0.0031) than Fe and Cu. Metal concentrations in water and brassica showed substantially more scattered behaviour on the plot and no meaningful relationship, although PCA and masked matrix correlation showed a fair association between Ni and Cu in brassica (r2: 0.46) and Fe and Ni in spinach (r2: 0.31). According to the study's findings, it is anticipated that special management and groundwater monitoring will be needed in the examined area to reduce the health risks related to drinking water that has been contaminated with metals.

Photocatalytic Degradation Studies of Organic Dyes over Novel Cu/Ni Loaded Reduced Graphene Oxide Hybrid Nanocomposite: Adsorption, Kinetics and Thermodynamic Studies

Nowadays, for environmental remediation, photocatalytic process involving graphene-based semiconductors is considered a very promising oxidation process for water treatment. In the present study, nanocomposite (Cu/Ni/rGO) has been synthesized by Dypsis lutescens leaf extract. Characterization of the sample was carried out by UV-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Different parameters like contact time, nanocatalyst amount, dye concentration, effect of temperature. and pH factor were optimized to examine the maximum removal efficiency for dyes rhodamine B and alizarine R with and without visible light source. In both cases, i.e., with or without light, maximum removal was observed at 20 mg of nanocatalyst for 5 ppm concentration of both dyes at 45 °C temperature and pH 10 for rhodamine B and pH 4 for alizarine R, respectively with a 20 min contact time. Maximum removal of dyes 93% rhodamine B and 91% alizarine R were observed under a tungsten lamp as compared to without a tungsten lamp, i.e., 78% of RhB and 75% of AR from mixture solution of these dyes. To assess the rate of reaction, spontaneity, and nature of reaction thermodynamics, kinetics and adsorption isotherms were studied. Thermodynamic values indicated that both dyes depicted endothermic and spontaneous degradation processes. Isotherm data fitted best to a Freundlich isotherm, while results of kinetic studies of both dyes followed the pseudo 2nd order kinetic equation. In the end, scavenging radical studies concluded that hydroxyl radicals were the main active specie involved in the photocatalytic degradation process, and regeneration experiments resulted that Cu/Ni/rGO nanocomposites were re-utilized for about four times.

Effectiveness of Opuntia ficus indica (cactus) fruit juice for sludge conditioning

The possibility of using Opuntia ficus indica fruit juice (OFIFJ) as a bioflocculant for conditioning the synthetic kaolin sludge and sewage sludge (region Oran, Algeria, and Pau, France) was studied. Turbidity of the supernatant, dryness of the sludge cake, and total time of filtration (TTF) were examined parameters. Using vacuum filtration, lime was also tested as a chemical conditioner and gives good results on Lescar (France) sewage sludge in terms of cake's dryness, filtrate quality, turbidity (13.54%), and total time of filtration (TTF = 85.29%), comparing to the industrial polymer (Sedifloc 408C; turbidity; 8.33% and TTF: 2.94%). For the sewage sludge of Oran (Algeria), the results obtained with OFIFJ were compared to those obtained with the cladodes juice of the same plant OFIC, and also with a cationic polymer (Superfloc 8396). For an optimum dosage, it showed that OFIFJ has a flocculation activity as same as the cladodes juice OFIC for sludge conditioning and gives better results in terms of turbidity (dosage of 22.4 g/kg DM: 3.7 NTU for OFIC, dosage of 8.36: 3.63 NTU for OFIFJ. Dryness was enhanced from 14.91 to 22.93% (OFIC 16 g/kg DM) and to 24.48% (OFIF 20.9 g/kg DM) but for TTF, we found the opposite. In fact, this plant showed to be an available, biodegradable, and non-toxic flocculant. For kaolin synthetic sludge (30%), the optimum dosages of those conditioners were found to be 0.066 g kg-1 for OFIC, comparing between vacuum filtration and filtration compression; turbidity was enhanced for both techniques, contrary to dryness. Concerning the Oran city sewage sludge, both turbidity and dryness were optimized. Same thing for the France sewage sludge, all the studied parameters were enhanced with the two studied bioflocculants.

Impact assessment of COVID-19 global pandemic on water, environment, and humans

One of the most significant threats to global health since the Second World War is the COVID-19 pandemic. Due to COVID-19 widespread social, environmental, economic, and health concerns. Other unfavourable factors also emerged, including increased trash brought on by high consumption of packaged foods, takeout meals, packaging from online shopping, and the one-time use of plastic products. Due to labour shortages and residents staying at home during mandatory lockdowns, city municipal administrations' collection and recycling capacities have decreased, frequently damaging the environment (air, water, and soil) and ecological and human systems. The COVID-19 challenges are more pronounced in unofficial settlements of developing nations, particularly for developing nations of the world, as their fundamental necessities, such as air quality, water quality, trash collection, sanitation, and home security, are either non-existent or difficult to obtain. According to reports, during the pandemic's peak days (20 August 2021 (741 K cases), 8 million tonnes of plastic garbage were created globally, and 25 thousand tonnes of this waste found its way into the ocean. This thorough analysis attempts to assess the indirect effects of COVID-19 on the environment, human systems, and water quality that pose dangers to people and potential remedies. Strong national initiatives could facilitate international efforts to attain environmental sustainability goals. Significant policies should be formulated like good quality air, pollution reduction, waste management, better sanitation system, and personal hygiene. This review paper also elaborated that further investigations are needed to investigate the magnitude of impact and other related factors for enhancement of human understanding of ecosystem to manage the water, environment and human encounter problems during epidemics/pandemics in near future.

Hydrothermally synthesized Ag-TiO2 nanofibers (NFs) for photocatalytic dye degradation and antibacterial activity

This work successfully utilised eco-friendly green synthesis to produce Ag-TiO₂ nanofibers (NFs). As pollution and energy limitations have become global issues, there is an ongoing need to develop more effective catalysts through straightforward and environmentally friendly methods. The Ag-TiO₂ nanofibers (NFs) XRD pattern exhibits an anatase TiO₂ and FCC crystal structure of Ag nanoparticles. The SEM investigation revealed a nanofiber-like surface morphology. The Ag-TiO₂ nanofibers (NFs) exhibits an optical band gap energy is 2.5 eV. Methylene blue (MB), malachite green (MG), Congo red (CR), and crystal violet (CV) dye aqueous solutions were used to evaluate the photocatalytic performance of the synthesized Ag-modified TiO₂ nanofibers (NFs) under direct sunlight irradiation. The effects of catalyst size on the efficient breakdown of MB dye were also investigated. The optimum catalyst concentration was found to be at 0.02 mg/mL. At 120 min of direct sunlight, the highest photosynthetic degradation efficiency (DE percentage) of 94% was achieved for MB dye. Ag-TiO₂ nanofibers (NFs) have been demonstrated to have exceptional antibacterial activity against Gram-positive bacteria such as Staphylococcus aureus and Gram-negative bacteria E-Coli. Because of these great qualities, it seems likely that the Ag-TiO₂ nanofibers (NFs) made could be a great photocatalyst for getting dye pollutants out of wastewater.

Biomolecule Protective and Photocatalytic Potential of Cellulose Supported MoS2/GO Nanocomposite

In the current study, cellulose/MoS2/GO nanocomposite has been synthesized by a hydrothermal method. Reports published regarding efficiency of Mo and graphene oxide-based nanocomposites for environmental remediation motivated to synthesize cellulose supported MoS2/GO nanocomposite. Formation of nanocomposite was initially confirmed by UV-visible and FTIR spectroscopic techniques. Particle size and morphology of the nanocomposite were assessed by scanning electron microscopy (SEM), and it was found having particle size ranging from 50 to 80 nm and heterogeneous structure. The XRD analysis also confirmed the structure of the nanocomposite having cellulose, MoS2, and GO. The synthesized nanocomposite was further tested for biomolecule protective potential employing different radical scavenging assays. Results of radical DPPH● (50%) and ABTS ●+ (51%) scavenging studies indicate that nanocomposites can be used as a biomolecule protective agent. In addition, nanocomposite was also evaluated for photocatalytic potential, and the results showed excellent photocatalytic properties for the degradation of 4-nitrophenol up to 75% and methylene blue and methyl orange up to 85% and 70%, respectively. So, this study confirmed that cellulose supported/stabilized MoS2/GO nanocomposite can be synthesized by an ecofriendly, cost-effective, and easy hydrothermal method having promising biomolecule protective and photocatalytic potential.

Facile synthesis and comparative study of the enhanced photocatalytic degradation of two selected dyes by TiO2-g-C3N4 composite

Photocatalysis is considered a useful technique employed for the dye degradation through solar light, visible or UV light irradiation. In this study, TiO₂, g-C₃N₄, and TiO₂-g-C₃N₄ nanocomposites were successfully synthesized and studied for their ability to degrade Rhodamine B (RhB) and Reactive Orange 16 (RO-16), when exposed to visible light. The analytical techniques including XRD, TEM, SEM, DRS, BET, XPS, and fluorescence spectroscopy were used to explore the characteristics of all the prepared semiconductors. The photocatalytic performance of synthesized materials has been tested against both the selected dyes, and various experimental parameters were studied. The experimental results demonstrate that, in comparison to other fabricated composites, the TiO₂-g-C₃N₄ composite with the optimal weight ratio of g-C₃N₄ (15 wt%) to TiO₂ has shown outstanding degrading efficiency against RhB (89.62%) and RO-16 (97.20%). The degradation experiments were carried out at optimal conditions such as a catalyst load of 0.07 g, a dye concentration of 50 ppm, and a temperature of 50 ℃ at neutral pH in 90 min. In comparison to pure TiO₂ and g-C₃N₄, the TiO₂-g-C₃N₄, a semiconductor, has shown higher degradation efficiency due to its large surface area and decreased electron-hole recombination. The scavenger study gave an idea about the primary active species (^-OH radicals), responsible for dye degradation. The reusability of TiO₂-g-C₃N₄ was also examined in order to assess the composite sustainability.

Recyclable Cu-Ag bimetallic nanocatalyst for radical scavenging, dyes removal and antimicrobial applications

An ecofriendly and cost effective green method has been used for the synthesis of recyclable, high functional nanoparticles. Bimetallic nanoparticles (BmNPs), Cu-Ag, have been synthesized using beetroot extract as reducing and capping agent. Formation of BmNPs was initially confirmed by UV-visible analysis, having distinct peaks of Ag at 429 nm and Cu at 628 nm. FTIR analysis also confirmed the association of bioactive phytochemicals with Cu-Ag nanoparticles. Crystallinity and morphology of BmNPs was determined through X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS) and energy dispersion X-ray spectroscopy (EDAX). The size of spherical shape Cu-Ag BmNPs was found to be 75.58 nm and EDAX studies confirmed the percent elemental composition of Cu and Ag in synthesized nanocatalyst. Results of different analysis provided supported evidences regarding the formation of BmNPs. Catalytic potential of BmNPs was tested for the degradation of rhodamine B (Rh-B), methylene blue (MB) and methyl orange (MO) dyes. Cu-Ag BmNPs exhibited outstanding catalytic activity for the degradation of selected organic dyes and percent degradation was recorded more than 90% for each dye. In addition, antiradical property of BmNPs was tested employing DPPH^● and ABTS^●+ assays and it was found to be promising. Synthesized BmNPs also exhibited strong antimicrobial activity against Salmonella typhimurium and Bacillus subtilis. Recyclability of nanoparticles was also evaluated and recovery from dye degradation reaction mixture was successfully achieved. The recovered nanoparticles exhibited same catalytic potential for the degradation of Rh-B. The objective of the current study was to synthesize BmNPs Cu-Ag employing a cost effective green method having promising catalytic, antiradical and antimicrobial potential. Further, BmNPs were reused after recovery from catalytic reactions, proving that BmNPs can be recycled having the same efficiency as that of a freshly prepared Cu-Ag BmNPs.

Excellent photocatalytic and antibacterial activities of bio-activated carbon decorated magnesium oxide nanoparticles

Green production of nanomaterials are restrict toxic substances and motivated the noxious free environment. Photocatalysis and antibacterial resistance are more promising and efficient fields for their chemical reductants and clean environment. Herein, we adopted a green and simple method for the biosynthesis of MgO NPs using Manilkara zapota as a bio source. Recently, the green synthesis of magnesium oxide nanoparticles has been a keen interest amongst researchers and scientists due to its simplicity eco-friendliness, non-toxic, inexpensive and potential to perform as an antibacterial agent. Activated carbon/Magnesium oxide (AC/MgO) photocatalyst was blended through a simple solution evaporation method. The surface electron microscopy (SEM) study reviles that AC/MgO had smooth and aggregated particles. The Fourier transform infrared (FT-IR) and x-ray diffraction (XRD) study confirms the structural formation and incorporation of nanoparticles into the AC matrix. Results confirmed the flourishing integration of MgO NPs over the activated carbon matrix. The electron movement and valency of AC/MgO photocatalyst reduced the bandgap and their findings were characterized by ultra visible diffuse reflectance spectroscopy (UV-DRS) and x-ray photoelectron spectroscopy (XPS). The blended AC/MgO photocatalyst was analyzed for photodegradation of Rhodamine- B (Rh-B) dye using a UV-visible spectrophotometer. The degradation study projects that the AC/MgO photocatalyst degrades (Rh-B) dye with 99% efficiency under simulated solar irradiation. This efficient degradation of (Rh-B) dye by AC/MgO photocatalyst is ascribed to the synergetic AC as catalytic support and adsorbent and MgO as photocatalyst. Finally, the photocatalytic material shows a better bactericidal effect in both gram-positive bacteria Escherichia coli-745 and gram-negative bacteria Staphylococcus aureus-9779. The AC/MgO photocatalyst is effectively used in bacteriocidal and photocatalytic removal of dyes and can be used for further development of water reuse and bio-medical fields. In addition, this research shows a viable method for synthesizing a cheap and effective AC/MgO for the photocatalytic destruction of organic pollutants.

Various advanced wastewater treatment methods to remove microplastics and prevent transmission of SARS-CoV-2 to airborne microplastics

Microplastics (MPs) and SARS-CoV-2 interact due to their widespread presence in our environment and affect the virus' behaviour indoors and outdoors. Therefore, it is necessary to study the interaction between MPs and SARS-CoV-2. The environmental damage caused by MPs is increasing globally. Emerging pollutants may adversely affect organisms, especially sewage, posing a threat to human health, animal health, and the ecological system. A significant concern with MPs in the air is that they are a vital component of MPs in the other environmental compartments, such as water and soil, which may affect human health through ingesting or inhaling. This work introduces the fundamental knowledge of various methods in advanced water treatment, including membrane bioreactors, advanced oxidation processes, adsorption, etc., are highly effective in removing MPs; they can still serve as an entrance route due to their constantly being discharged into aquatic environments. Following that, an analysis of each process for MPs' removal and mitigation or prevention of SARS-CoV-2 contamination is discussed. Next, an airborne microplastic has been reported in urban areas, raising health concerns since aerosols are considered a possible route of SARS-CoV-2 disease transmission and bind to airborne MP surfaces. The MPs can be removed from wastewater through conventional treatment processes with physical processes such as screening, grit chambers, and pre-sedimentation.

SARS-CoV-2 removal by mix matrix membrane: A novel application of artificial neural network based simulation in MATLAB for evaluating wastewater reuse risks

The COVID-19 outbreak led to the discovery of SARS-CoV-2 in sewage; thus, wastewater treatment plants (WWTPs) could have the virus in their effluent. However, whether SARS-CoV-2 is eradicated by sewage treatment is virtually unknown. Specifically, the objectives of this study include (i) determining whether a mixed matrixed membrane (MMM) is able to remove SARS-CoV-2 (polycarbonate (PC)-hydrous manganese oxide (HMO) and PC-silver nanoparticles (Ag-NP)), (ii) comparing filtration performance among different secondary treatment processes, and (iii) evaluating whether artificial neural networks (ANNs) can be employed as performance indicators to reduce SARS-CoV-2 in the treatment of sewage. At Shariati Hospital in Mashhad, Iran, secondary treatment effluent during the outbreak of COVID-19 was collected from a WWTP. There were two PC-Ag-NP and PC-HMO processes at the WWTP targeted. RT-qPCR was employed to detect the presence of SARS-CoV-2 in sewage fractions. For the purposes of determining SARS-CoV-2 prevalence rates in the treated effluent, 10 L of effluent specimens were collected in middle-risk and low-risk treatment MMMs. For PC-HMO, the log reduction value (LRV) for SARS-CoV-2 was 1.3-1 log10 for moderate risk and 0.96-1 log10 for low risk, whereas for PC-Ag-NP, the LRV was 0.99-1.3 log10 for moderate risk and 0.94-0.98 log10 for low risk. MMMs demonstrated the most robust absorption performance during the sampling period, with the least significant LRV recorded in PC-Ag-NP and PC-HMO at 0.94 log10 and 0.96 log10, respectively.

Fabrication of graphene-oxide and zeolite loaded polyvinylidene fluoride reverse osmosis membrane for saltwater remediation

Incorporation of inorganic and organic materials in polymer has contributed well towards the development of advanced reverse-osmosis membranes; with greater permeation, and salt rejection potential. We are reporting, Zeolite/GO/PVDF based thin-film composite membranes that were successfully synthesized by solution casting process, an eco-friendly, low-cost, and biocompatible technique. PVDF membranes modified with different ratios of GO/Zeo (0.03, 0.05 and 0.07) were characterized by FTIR, SEM, XRD, TGA, and DSC. Membranes were then tested for its potential for water permeation and salt rejection abilities. As prepared membranes owe better pore-distribution, a moderate degree of crystallinity and high absorption capability that is highly needed for micro-filtration phenomena used for desalination of saline water. The modified membranes exhibited enhanced water permeability up to 28.9 L/m²h as compared to pure PVDF membrane having water permeability flux of 15.6 L/m²h. Salt-rejection ability was found increasing for the membranes (up to 98%) modified with different concentration of GO/Zeo, as compare to pure PVDF membrane (82%). During water permeation and salt rejection studies, no deleterious impact was noted for modified PVDF membranes. This development will entail an efficient approach to furnish high-level performance reverse-osmosis membranes, with greater osmotic-pressure bearing capacity and higher stability.

Critical role of Hyssop plant in the possible transmission of SARS-CoV-2 in contaminated human Feces and its implications for the prevention of the virus spread in sewage

The significant issue affecting wastewater treatment is human faeces containing SARS-CoV-2. SARS-CoV-2, as a novel coronavirus, has expanded globally. While the current focus on the COVID-19 epidemic is rightly on preventing direct transmission, the risk of secondary transmission via wastewater should not be overlooked. Many researchers have demonstrated various methods and tools for preventing and declining this virus in wastewater treatment, especially for SARS-CoV-2 in human faeces. This research reports two people tested for 30 d, with written consent, at Mosa-Ebne-Jafar Hospital of Quchan, Iran, from September 1st to October 9th, 2021. The two people's conditions are the same. The Hyssop plant was used, which boosts the immune system's effectiveness and limonene, rosemary, caffeic acids and flavonoids, all biologically active compounds in this plant, cause improved breathing problems, colds, and especially for SARS-CoV-2. As a result, utilising the Hyssop plant can help in reducing SARS-CoV-2 in faeces. This plant's antioxidant properties effectively reduce SARS-CoV-2 in faeces by 30%; nevertheless, depending on the patient's condition. This plant is also beneficial for respiratory and digestive health.

Integration of renewable energy in wastewater treatment during COVID-19 pandemic: Challenges, opportunities, and progressive research trends

SARS-CoV-2 has aroused drastic effects on the global economy and public health. In response to this, personal protective equipment, hand hygiene, and social distancing have been considered the most important ways to prevent the direct spread of the virus. SARS-CoV-2 would be possible survive in wastewater for a few days, leading to secondary transmission via contact with water and wastewater. Thus, the most economical and practical approaches for decentralized wastewater treatment are renewable energies such as the solar energy disinfestation process. However, as freshwater requirements increase and fossil fuels become unsustainable, renewable energy becomes more attractive for desalination applications. Solar photovoltaic, membrane-based, and electricity desalination technologies are becoming increasingly popular due to their lower energy requirements. Several aquatic environments could be benefitted from solar energy wastewater disinfection. Besides, utilizing solar energy during the day can inactivate SARS-CoV-2 to nearly 90%. However, conventional membrane-based desalination practices have also been integrated, including reverse osmosis (RO) and electrodialysis (ED). Several exciting membrane processes have been developed recently, including membrane distillation (MD), pressure-reduced osmosis (PRO), and reverse electrodialysis (RED). Such operations can produce clean and sustainable electricity from brine and impaired water, generally considered hazardous to the environment. As a result, neither PRO nor RED can produce electricity without mixing a high salinity solution (such as seawater or brine and wastewater, respectively) with a low salinity solution. Herein, we critically review the progress in applying renewable energy such as solar energy and geothermal energy for generating electricity from wastewater treatment and uniquely discuss the effects of these two types of renewable energy on SARS-CoV-2 in air and wastewater treatment. We also highlight the significant process made on the membrane processes utilizing renewable energy and research gaps from the standpoint of producing clean and sustainable energy. The significant points of this review are: (1) among various types of renewable energy, solar energy and geothermal energy have been predominantly studied for wastewater treatment, (2) effects of these two types of renewable energy on SARS-CoV-2 in air and wastewater treatment are critically analyzed, and (3) the knowledge gaps and anticipated future research outlook have been consequently proposed thereof.

Persistent organic pollutants in water resources: Fate, occurrence, characterization and risk analysis

Persistent organic pollutants (POPs) are organic chemicals that can persist in the environment for a longer period due to their non-biodegradability. The pervasive and bio-accumulative behavior of POPs makes them highly toxic to the environmental species including plants, animals, and humans. The present review specifies the POP along with their fate, persistence, occurrence, and risk analysis towards humans. The different biological POPs degradation methods, especially the microbial degradation using bacteria, fungi, algae, and actinomycetes, and their mechanisms were described. Moreover, the source, transport of POPs to the environmental sources, and the toxic nature of POPs were discussed in detail. Agricultural and industrial activities are distinguished as the primary source of these toxic compounds, which are delivered to air, soil, and water, affecting on the social and economic advancement of society at a worldwide scale. This review also demonstrated the microbial degradation of POPs and outlines the potential for an eco-accommodating and cost-effective approach for the biological remediation of POPs using microbes. The direction for future research in eliminating POPs from the environmental sources through various microbial processes was emphasized.

Contamination, exposure, and health risk assessment of Hg in Pakistan: A review

Mercury is a highly toxic and highly mobile heavy metal. It has been regarded as more toxic than other nonessential and toxic nonradioactive heavy metals. Moreover, it has a high tendency of bioaccumulation and biomagnification in the ecosystem. This study aimed to assess the environmental and health risks related to Hg. Seventy studies related to Hg in environmental media, aquatic biota, and food stuffs across Pakistan were reviewed, and their concentrations were used for ecological and human health risk assessments. High concentrations of Hg were reported in the environment, with maximum concentrations of 72 mg L^-1, 144 mg kg^-1, 887 mg kg^-1, and 49,807 ng m^-3 in surface water, surface soil, surface sediments, and urban atmosphere, respectively. The possible non-carcinogenic health risk (hazard quotient) of Hg was assessed in soil, water, and fish. High risks were calculated for seafood and vegetable consumption, while low risks were estimated for soils and groundwater ingestion and exposure. Overall, children showed higher risks than adults. Last, the risk quotient analysis (RQ) revealed significant risks for aquatic species. RQs showed that multiple species, especially those with smaller resilience, could face long-term detrimental impacts. High, medium, and low risks were calculated from 66.66, 16.17, and 16.17% of the reported Hg concentrations.

Mercury sources and physicochemical characteristics in ice, snow, and meltwater of the Laohugou Glacier Basin, China

In this work, samples of surface snow, surface ice, snow pit and meltwater from the Laohugou Glacier No. 12 on the northern edge of Tibetan Plateau (TP) were collected during the summer of 2015. The average concentration of Hg in surface snow/ice was 22.41 ng L^-1, while the percentage of dissolved mercury (Hg_D) was observed to be around 26%. An altitudinal magnification of Hg was not observed for surface snow; however, in contrast, a significant positive magnification of Hg with altitude was observed in the surface ice. A higher concentration of Hg corresponded with the dust layer of the snow pit. It was observed that about 42% of Hg was lost from the surface snow when the glacier was exposed to sunlight within the first 24 h indicating some Hg was emitted back to the atmosphere while some were percolated downwards. The result from the principal component analysis (PCA) showed that the sources of Hg in Laohugou Glacier No. 12 were from crustal and biomass burning. Finally, it was estimated that total export of Hg from the outlet river of Laohugou glacier No. 12 in the year 2015 was about 1439.46 g yr^-1 with yield of 22.77 μg m² yr^-1. This study provides valuable insights for understanding the behavior of Hg in the glacier of the northern Tibetan Plateau.

An overview on non-spherical semiconductors for heterogeneous photocatalytic degradation of organic water contaminants

Because of their carcinogenicity and mutagenicity, the elimination of organic contaminants from surface and subsurface water is a subject of environmental significance. Conventional water decontamination approaches such as membrane separation, ultrafiltration, adsorption, reverse osmosis, coagulation, etc., have relatively higher operating costs and can generate highly toxic secondary contaminants. On the other hand, heterogeneous photocatalysis, an advanced oxidation process (AOP), is considered a clean and cost-effective process for organic pollutants degradation. Owing to their distinctive structure and physicochemical properties non-spherical semiconductors have gained considerable limelight in the photocatalytic degradation of organic contaminants. The current review briefly introduces a wide range of organic water contaminants. Recent advances in non-spherical semiconductor assembly and their photocatalytic degradation applications are highlighted. The underlying mechanism, fundamentals of photocatalytic reactions, and the factors affecting the degradation performance are also alluded including the current challenges and future research perspectives.

Ionic liquid-based antimicrobial materials for water treatment, air filtration, food packaging and anticorrosion coatings

Efforts to widen the scope of ionic liquids applications across diverse research areas have flourished in the last two decades with developments in understanding and tailoring their physical, chemical, and biological properties. The promising applications of ionic liquids-based materials as antimicrobial systems is due to their ability and flexibility to be tailored in varying sizes, morphologies, and surface charges. Ionic liquids are also considered as greener materials. Common methods for the preparation of ionic liquid-based materials include crosslinking, loading, grafting, and combination of ionic liquids with other polymeric materials. Recent research focuses on the tuning of the biological properties to design novel ionic liquids-based antimicrobial materials. Here, the properties, synthesis and applications of ionic liquids and ionic liquids-based materials are reviewed with focus on antimicrobial activities applied to water treatment, air filtration, food packaging, and anticorrosion.

Cytotoxic aquatic pollutants and their removal by nanocomposite-based sorbents

Water is an extremely essential compound for human life and, hence, accessing drinking water is very important all over the world. Nowadays, due to the urbanization and industrialization, several noxious pollutants are discharged into water. Water pollution by various cytotoxic contaminants, e.g. heavy metal ions, drugs, pesticides, dyes, residues a drastic public health issue for human beings; hence, this topic has been receiving much attention for the specific approaches and technologies to remove hazardous contaminants from water and wastewater. In the current review, the cytotoxicity of different sorts of aquatic pollutants for mammalian is presented. In addition, we will overview the recent advances in various nanocomposite-based adsorbents and different approaches of pollutants removal from water/wastewater with several examples to provide a backdrop for future research.

Superior performance of FeVO4@CeO2 uniform core-shell nanostructures in heterogeneous Fenton-sonophotocatalytic degradation of 4-nitrophenol

Porous FeVO₄ nanorods decorated on CeO₂ nanocubes (FeVO₄@CeO₂) were successfully prepared via a facile hydrothermal route and tested in the degradation of 4-nitrophenol (4-NP) for enhanced heterogeneous oxidation using ultrasonic (US), ultraviolet (UV), and binary irradiation US/UV, respectively. The nanostructure of the core-shell FeVO₄@CeO₂ was characterised using XRD, SEM, EDS elemental mapping, TEM, HRTEM, SAED, FTIR, Raman, BET, point of zero charge (PZC), XPS analysis and UV-vis DRS. The effect of various parameters, for examples, nanostructured core-shell amounts, hydrogen peroxide concentration, initial concentration, pH and irradiation time, on 4-NP degradation were investigated for the optimisation of the catalytic performance. The durability and stability of the core-shell nanostructured materials were also investigated and the obtained results revealed that the catalysts can endure the harsh sonophotocatalytic conditions even after six cycles. Mineralisation experiments were investigated using the optimised parameters. The core-shell nanostructured FeVO₄@CeO₂ has higher PZC than pure FeVO₄ and CeO₂, leading to excellent sonophotocatalytic activity even at high pH and stability for the degradation of 4-NP after six cycles. A possible mechanism over the FeVO₄@CeO₂ was proposed based on the special three-way Fenton-like mechanism and the dissociation of H₂O₂ with the experiments of active species trapping and calculated band gap energy.

Sulfur extraction from liquid fuels using trihexyl(tetradecyl)phosphonium tetrafluoroborate: as promising solvent

Sulfur extraction from fuel is essential to be done for environmental and industrial point of view. Extractive desulfurization (EDS) is one of the most promising techniques in order to achieve legislative sulfur content requirements. Among numerous extractants and solvents, ionic liquids (ILs) are more capable due to their desirable green solvent properties. This work demonstrated that trihexyl(tetradecyl)phosphonium tetrafluoroborate ([THTDP]BF₄) was synthesized, characterized, and employed as extraction solvent for extraction of dibenzothiophene (DBT), thiophene, benzothiophene, and other alkyl-substituted derivatives of sulfur from liquid fuel. Molecular confirmation and purity of synthesized ([THTDP]BF₄) were analyzed with FTIR, Raman, NMR, EPR, UV, TG/DSC, and XRD analyses. Also, physical properties of ([THTDP]BF₄) were carried out. The effects of extraction time, temperature, sulfur compounds, ultra-sonication, and ([THTDP]BF₄) recycling/regeneration on DBT removal from liquid fuel were also examined. DBT removal in n-dodecane was 92.6% using EDS with mass ratio (1:1) in 30 min at 30 °C under the mild reaction conditions. ([THTDP]BF₄) could be reused up to ten cycles for sulfur extraction and regenerated for few more cycles with good DBT removal ability. Also, the sulfur extraction from real fuels and multistage extraction performance were tested. The experimental data and results provided in this article discover the remarkable understandings of tetrafluoroborate-based phosphonium ionic liquids as promising solvent for EDS.

Response surface methodology approach for optimization of methyl orange adsorptive removal by magnetic chitosan nanocomposite

In this work, the adsorption process of methyl orange (MO) removal by a magnetic chitosan with an Al2O3/Fe3O4 core was optimized using the experimental design method in order to maximize the removal efficiency. Response surface methodology (RSM) based on central composite design (CCD) was performed to find the relationship between the effective adsorption parameters on the MO removal efficiency as the response. The statistical parameters of the derived model were acquired: R2 = 0.9799 and F value = 47.07. Finally, non-linear optimization was carried out and values of 6.5, 0.70 g l–1, 30 ppm, and 60 min were obtained as the optimum values for pH, adsorbent dosage, initial concentration, and contact time, respectively, while the predicted MO removal efficiency was found to be 96.8 ± 2.2% (with a 95% confidence level). This was in agreement with the experimental response of 96.5 ± 1.4%.

Protocol for development of various plants leaves extract in single-pot synthesis of metal nanoparticles

This article is aimed to extend a simple protocol for preparation of various plant leaves extract and their application to green synthesis of the metallic nanoparticles. Five plant leaves extract showed mild reduction and stabilization ability for silver and gold nanoparticles (AgNPs and AuNPs) at room temperature. The particle size range varied from 25 to 42 nm and 21 to 47 nm for AgNPs and AuNPs, respectively. Plant leaves extract-mediated nanoparticles were characterized to confirm the shape, size, crystallinity, and content using different spectroscopic investigations. Differences in stability of nanoparticles at different pH were also measured by zeta potential.

Remediation of hexachlorobenzene in soil by enhanced electrokinetic Fenton process

The feasibility of enhanced electrokinetic Fenton process for the remediation of Hexachlorobenzene (HCB) in low permeability soil was investigated. Kaolin was artificially contaminated with HCB and treated by electrokinetic and electrokinetic Fenton processes. beta -Cyclodextrin was used to enhance the solubility of HCB in pore fluid. Three tests were carried out, of which two were electrokinetic experiments to observe the suitability of beta -cyclodextrin as a flushing solution for these processes. The third experiment was the electrokinetic Fenton test using beta -cyclodextrin as an enhancing agent. Results show that the removal efficiency depends on the choice of a suitable flushing solution and physical parameters like pH, electric current and electro-osmotic flow.