Contamination Of Water Resources Research Articles

Predicting and modelling availability of fluoride in soil from sorption properties

AbstractUsage of alkaline and saline groundwater with elevated concentrations of fluoride (F−) for irrigation of pastures requires an assessment of the mobility of F− within the plant‐water‐soil continuum. Factors influencing F− sorption and desorption in 95 Australian soils were examined. Pronounced differences in F− sorption were observed across the soils, but these differences could not be explained by differences in soil pH, electrical conductivity or organic carbon. Rather, sorption was correlated with the content of Fe/Al hydrous oxides and kaolinite in soil. Sorption of F− onto soils increased the solution pH and the ratio of (F− adsorbed) to (OH− desorbed) was consistently below 1, thereby indicating that adsorption of F− results in the release of water and hydroxyl groups from, or co‐adsorption of protons to, the sorbent surface. Maximum sorption occurred at pH values of approximately 5–6, whilst sulphate slightly increased (<5%) F− sorption. Desorption was slightly decreased (~3%–7%) in presence of sulphate anions. Hence, it is unlikely that irrigation of soil with alkaline and saline groundwater, in combination with soil applications of gypsum and sulphur to limit pH fluctuations, would increase mobility of F− in soil. Finally, the irrigation of soil columns with 1200–1500 mm of alkaline and saline groundwater containing 0.18 mM F−, as would commonly occur in irrigation systems using coal seam gas associated water in Australia, resulted in a F− concentration of 0.05 mM at 10 cm depth and the measured values were in excellent agreement with modelled F− movement based on sorption parameters. Thus, sorption parameters can be used to identify soils which minimize movement of F− because of their strong F− sorption. Based on these results, safe limits for irrigation of soil can be established which avoid F− toxicity risks to plants, animals and contamination of water resources.

Anthropogenic nitrate contamination of water resources in Ethiopia: an overview

Abstract Nitrate is one of the water contaminants that mainly results from anthropogenic activities. The major causes of nitrate contamination of water resources are anthropogenic activities such as animal or human waste, septic or sewage systems, fertilizer application, concentrated animal farming, industrial waste, and landfill leachates. These man-made activities are the primary sources of nitrate contamination in water resources. Nitrate contamination of water is a global issue that has been increasing over time. According to previous research, exposure to nitrate in water above the World Health Organization (WHO) guideline limit (50 mg of NO3/L) has been found to induce major health effects such as methemoglobinemia in humans, with the severity depending on the amount consumed. This problem has become a major threat to humans and the environment. Thus, this article presented an overview of nitrate contamination of water resources in Ethiopia, emphasizing anthropogenic activities to indicate the current nitrate water contamination status for the necessary remedial actions.

Sugar-Based Phase-Selective Supramolecular Self-Assembly System for Dye Removal and Selective Detection of Cu2+ Ions.

Simple, effective, and eco-friendly sugar-based phase-selective gelators were synthesized at a low cost. They showed high gelling ability toward a wide range of solvents at lower concentrations (minimum gelation concentration ∼0.3%). Preliminary tests reveal that these low molecular weight organogelators can immediately and phase-selectively gel benzene, toluene, petrol, and kerosene in water at room temperature. We also identified G13 in toluene as the good gelator, and the corresponding organogel proficiently removes water-soluble dyes from their concentrated aqueous solutions. This efficient removal of toxic organic solvents and dyes from water suggests promising applications in removing organic substances from contaminated water resources. The thermoreversible gel exhibits effective rechargeability up to five cycles of burning and gelation, which imply the flame stability of the gel. Interestingly, these compounds had a high detection ability toward Cu2+ ions with a state change from gel to the solution. The physical justification for gelation mechanisms and the molecular interaction with metal ions were further confirmed by computational studies.

Heavy Metal Removal with NanoTiO2/Chitosan Modified Poly(Vinylidene Chloride)

Background: Heavy metal contamination of water resources has been identified as one of the most serious environmental issues. Chemical modification of hydrophobic polymer matrices is another approach for changing their surface properties for water treatment. The addition of nanoparticles to polymers alters surface characteristics such as adsorption capacity, adhesion, catalytic ability, and wettability to heavy metals in wastewater. Objective: Evaluation of the nanomodified polyvinyl chloride (PVC) polymer as a heavy metal adsorbent from wastewater. Methods: In the field of emission discharges from industries and domestic wastes that contain unknown inorganic pollutants by PVC using grafting chitosan/TiO2 nanocomposites. The characterization of different thin films was performed using TEM, XRD, and FTIR. The metal concentrations were measured by using inductively coupled plasma (ICP-OES). Results: Nanomodification of PVC was evaluated by infrared spectroscopy. The presence of chlorine in the PVC structure before and after the nanomodification is confirmed by the presence of a peak at 690 cm-1 attributed to the axial deformation of the C-Cl bond. The nanomodified PVC showed an ion exchange capacity of 1.27 mmol-1 , and efficiently removed the heavy metals from aqueous solutions. The heavy metal removal effectiveness (R) was improved by increasing the concentration of TiO2 nanoparticles. The amount adsorbed per gram of adsorbent (Qe) was computed and revealed that the amount of adsorption increased for nanomodified PVC thin film as compared to 100% PVC thin film. The nanomodified PVC thin film showed high stability for 4 cycles of use. This improvement has been attributed to the nanomodified PVC polymer's large surface area (ranging from 0.3 to 282 m2 /g). Conclusion: The modification of PVC with nanoparticles increases the cost of PVC thin film by 15%. However, it offers efficiency 3 times than the original PVC.

Influence of Doping-Ion-Type on the Characteristics of Al2O3-Based Nanocomposites and Their Capabilities of Removing Indigo Carmine from Water

Globally, the continuous contamination of natural water resources is a severe issue, and looking for a solution for such a massive problem should be the researcher’s concern. Herein, Al2O3, Al2O3-CuO, Al2O3-NiO, and Al2O3-CoO were prepared via a simple and fast route, utilizing glucose as a capping material. All synthesis conditions were uniform to make the fabricated nanomaterials’ characteristics exclusively influenced by only the ion type. The SEM analysis showed that the particles of the synthesized Al2O3, Al2O3-CuO, Al2O3-NiO, and Al2O3-CoO were all less than 25 nm. The Al2O3-NiO showed the smallest particle size (11 to 14 nm) and the best BET surface area of 125.6 m2 g−1. All sorbents were tested for removing organic pollutants, as exemplified by indigo carmine (IGC) dye. The Al2O3-NiO possessed the highest adsorption capacity among the other sorbents for which it had been selected for further investigations. The IGC sorption reached equilibrium within 2.0 h, and the kinetic study revealed that the IGC removal by Al2O3-NiO nanocomposite fitted the FOM and the LFM. The sorbent showed an experimental adsorption capacity (qt) of 456.3 mg g−1 from a 200 mg L−1 IGC solution and followed the Langmuir model. The thermodynamic findings indicated an endothermic, spontaneous, and physisorption nature. The seawater and groundwater samples contaminated with 5.0 mg L−1 IGC concentrations were fully remediated using the Al2O3-NiO nanocomposite. The reuse study showed 93.3% average efficiency during four successive cycles. Consequently, prepared Al2O3-NiO nanocomposite is recommended for the treatment of contaminated water.

Effects of aquatic heavy metal intoxication on the level of hematocrit and hemoglobin in fishes: A review

Environmental pollution caused due to the presence of heavy metals has become a great concern as it has an adverse effect on almost all types of ecosystem. In this sense, these pollutants have a tendency to pollute the aquatic ecosystem, thus badly affecting the health of aquatic organisms. As a result, toxicological studies believe them to be the most harmful pollutants in the aquatic environment. Among all the aquatic organisms, fish—being a chief organism in this system—become the easiest victim of these pollutants. Heavy metals enter fish bodies through the alimentary system by consumption of polluted food, or through the gills, and skin. They are finally delivered by the bloodstream to the organs and tissues where they accumulate after absorption. Ultimately, in this way heavy metals make their way into humans through the food chain. The fluctuations in the hematological values may serve as an initial indicator of the toxicant’s impact on fish health. It has been observed that when pollutants impact the quality of the aquatic medium, the first consequence is apparent in the form of physiological changes in fish, which are reflected in one or more hematological parameters, such as hemoglobin, hematocrit, red blood cell count, white blood cell count, etc. As a result of these alterations, fish become weak, anemic, and more susceptible to diseases. Over the past several decades, a vast number of studies have been reported on the qualitative and quantitative variations in hematological parameters due to the presence of heavy metal intoxication. Heavy metal contamination of water resources not only degrades the water quality but also negatively impacts the quality of food in the form of fish proteins. Therefore, this article sheds light on the effects of heavy metals on hemoglobin and hematocrit of fish hematology and calls for more attention to the protection and preservation of aquatic ecosystems, particularly those contaminated with heavy metals.

Peroxydisulfate activation by enhanced catalytic activity of CoFe2O4 anchored on activated carbon: A new sulfate radical-based oxidation study on the Cefixime degradation

This work focused mainly on anchoring cobalt ferrite (CF) nanoparticles onto the surfaces of activated carbon (AC) for preparation of recoverable AC@CF composite as a heterogeneous peroxydisulfate (PDS) activator towards cefixime (CEF) degradation. Catalytic-mediated PDS activation potential of CF nanoparticles was significantly enhanced after anchoring onto the AC surfaces, indicating the efficient role of AC in inhibition of CF agglomeration. AC@CF/PDS system could achieve the complete degradation of CEF (with the reaction rate constant of 0.11 min−1) and 63.7% mineralization within only 40 min in the presence of 0.4 g/L catalyst and 3.0 mM PDS at pH 7.0. Comparative tests verified a strong synergistic effect (with synergy factor value of 2.75) between AC@CF and PDS towards CEF decontamination. The possible mechanisms of PDS activation, the generation of reactive species and the degradation pathway were proposed and discussed in details. AC@CF showed an excellent recyclability and stability in terms of CEF and TOC elimination and the removal efficiencies of 82.4 and 46.7% were attained in the fifth cycle, respectively. The quantity of leached metal ions from the catalyst surface to the reaction solution in each studied cycle was approximately < 2 % mass of used AC@CF. Based on the reactive species capture tests, the importance of their contribution in degradation process was in order of: SO4•– > HO• > O2•−. This work provides the key role of AC in improving the CF catalytic activity for activating PDS and efficient degradation of antibiotics from contaminated-water resources with high performance and safe application.

Thermal degradation of emerging contaminants in municipal biosolids: The case of pharmaceuticals and personal care products

The presence of emerging contaminants in water and wastewater resources is of ongoing concern for public health and safety. Pharmaceutical compounds are designed to be biologically active and therefore may have effects on nontarget organisms in terrestrial and aquatic environments, even at trace concentrations. The presence of pharmaceutical and personal care products (PPCPs) in wastewater treatment plants is reported in various countries worldwide, mostly in the levels of nanograms to micrograms per litre. The present study investigates the thermal degradation of municipal sewage sludge containing PPCPs at various heating rates. The examined characteristics of the samples include thermal decomposition behavior, volatile release characteristics, and pyrolytic product composition. Thermal characterization of the PPCPs was conducted using differential scanning calorimetry. The gaseous products and typical functional groups of the released volatiles detected by Fourier-transform infrared spectroscopy mainly contained CO2, CO, small-chain hydrocarbons, and oxygen- and nitrogen-containing functional groups together with other species. In addition, the potential of bioenergy production was investigated as a spin-off opportunity during thermal degradation of biosolids. Study results showed that PPCP concentrations can be lowered significantly by thermal treatment of municipal biosolids. Antifungal/antibacterial agents together with opioids, in particular triclosan and tramadol, showed less resistance to thermal degradation while antibiotics could be more recalcitrant to heat treatment. The thermodynamic results provide an important reference for future reactor design and the thermochemical treatment of biosolids as well as their conversion to value-added products.

Phytoremediation of heavy metals in soil and water: An eco-friendly, sustainable and multidisciplinary approach.

Rapid industrialization, increased waste production and surge in agricultural activities, mining, contaminated irrigation water and industrial effluents contribute to the contamination of water resources due to heavy metal (HM) accumulation. Humans employ HM-contaminated resources to produce food, which eventually accumulates in the food chain. Decontamination of these valuable resources, as well as avoidance of additional contamination has long been needed to avoid detrimental health impacts. Phytoremediation is a realistic and promising strategy for heavy metal removal from polluted areas, based on the employment of hyper-accumulator plant species that are extremely tolerant to HMs present in the environment/soil. Green plants are used to remove, decompose, or detoxify hazardous metals in this technique. For soil decontamination, five types of phytoremediation methods have been used viz. phytostabilization, phytodegradation, rhizofiltration, phytoextraction and phytovolatilization. Traditional phytoremediation methods, on the other hand, have significant limits in terms of large-scale application, thus biotechnological efforts to modify plants for HM phytoremediation ways are being explored to improve the efficacy of plants as HM decontamination candidates. It is relatively a new technology that is widely regarded as economic, efficient and unique besides being environment friendly. New metal hyperaccumulators with high efficiency are being explored and employed for their use in phytoremediation and phytomining. Therefore, this review comprehensively discusses different strategies and biotechnological approaches for the removal of various HM containments from the environment, with emphasis on the advancements and implications of phytoremediation, along with their applications in cleaning up various toxic pollutants. Moreover, sources, effects of HMs and factors affecting phytoremediation of HMs metals have also been discussed.

Preparation of dual Z-scheme PDIP/WO3@CN-Br heterojunction photocatalyst and its excellent degradation efficiency of tetracycline under visible light

The novel all-solid PDIP/WO3@Br-doped g-C3N4 (PDIP/WO3@CN-Br) composite with a dual Z-scheme heterojunction structure was designed to remove tetracycline contaminants in water resources. The obvious improvement on the degradation efficiency for tetracycline not only originates from the more active sites provided by this system, but also results from the extended carrier life of the special heterojunction structure. Moreover, the introduction of the cocatalyst Br changes the microstructure of bulk g-C3N4 to accelerate the separation of electrons and holes, thus improving the photocatalytic performance. Upon these advantageous merits, the apparent rate constant of tetracycline degradation by the PDIP/WO3@CN-Br photocatalyst was 3.83 times higher than that of pure PDIP. Additionally, two typical degradation pathways for tetracycline were hypothesized by LC-MS and 3DEEMs tests, which systematacially demonstrated this pollutant has transformed into small molecule substances. Satisfactorily, in the simulation experiments of different water environments, this PDIP/WO3@CN-Br system showed excellent stability and practical application value. Our study provides a promising approach to design a novel dual Z-scheme heterojunction photocatalysts with full utilization of solar energy and enhance charge separation.

A partial least squares-path model of environmental degradation in the Paraopeba River, for rainy seasons after the rupture of B1 tailings dam, Brumadinho, Brazil

The present study aimed to investigate the rupture of B1 tailings dam of Córrego do Feijão mine, which drastically affected the region of Brumadinho (Minas Gerais, Brazil). The contamination of water resources reached 155.3 km from the dam site. In the river channel, high concentrations of Mn, Al, As and Fe were detected and correlated to the spillage of the tailings in the river. The presence of the tailings also affected the chlorophyll-a content in the water, as well as the reflectance of riparian forests. With the increase of metal(oid) concentrations above permitted levels, water management authorities suspended the use of Paraopeba River as resource in the impacted areas, namely the drinking water supply to the Metropolitan region of Belo Horizonte. This study aimed to evaluate possible links between tailings distribution, river water quality, and environmental degradation, which worked as latent variables in partial least squares regression models. The latent variables were represented by numerous physical and chemical parameters of water and sediment, measured four times in 22 locations during the rainy season of 2019, in addition to stream flow and to NDVI evaluated in satellite images processed daily. The modeling results suggested a relationship between river flow turbulence and increased arsenic release from sand fractions, as well as desorption of Mn from metal oxides, both representing causes of water quality reduction. They also revealed increasing iron concentrations affecting the forest NDVI (greening), which was interpreted as environmental degradation. The increase of chlorophyll-a concentrations (related with turbidity decreases), as well as the increase of river flows (responsible for dilution effects), seemed to work out as attenuators of degradation. Although applied to a specific site, our modeling approach can be transposed to equivalent dam failures and climate contexts, helping water resource management authorities to decide upon appropriate recovery solutions.

Remediation of Microcystis aeruginosa blooming water using a reusable polyethylenimine–polyvinyl chloride composite adsorbent

This study aimed to apply an adsorption-based technique to directly suppress harmful algal blooms (HABs) in freshwater without causing secondary pollution. Considering the negative surface charge of the representative harmful cyanobacteria Microcystis aeruginosa of HABs in the aqueous phase, a stable and aminated sorbent polyethylenimine–polyvinyl chloride composite fiber (PEI–PVC) was applied to remove M. aeruginosa cells from the aqueous solution. The PEI–PVC fiber could directly and efficiently remove approximately 90 % of harmful cyanobacterial cells in artificial media and approximately 80 % of HABs in real environmental water without any cell lysis or destruction. During the HAB treatment process using PEI–PVC, the amount of microcystins (MCs) in the test sample was continuously decreased by simultaneous adsorption on the PEI–PVC. The PEI–PVC fiber used in this study was regenerable through desorption using an alkaline solution, and the regenerated adsorbent showed a similar cell removal efficiency to that of the original adsorbent. In addition, under light exposure, the PEI–PVC fiber did not elute any toxic chlorine into the solution, whereas pristine PVC fiber increased the chlorine concentration in the aqueous solution through photodegradation. Consequently, the adsorption-based method using PEI–PVC fiber could be a feasible and stable method for counteracting HAB contamination of water resources.

Adsorption of arsenic in aqueous solution onto iron impregnated bagasse fly ash.

The present study examined the adsorption of As(III) and As(V) (arsenics) from aqueous solutions using FeCl3 impregnated bagasse fly ash (BFA-Fe). Batch adsorption studies were carried out to evaluate the effect of various parameters like initial pH (pH 0 ), adsorbent dose (m), contact time (t), initial concentration (C 0 ) and temperature (T) on the removal of As(III) and As(V) from aqueous solutions. The maximum removal of As(III) and As(V) was found ~ 95% and ~ 97% at lower concentration (< 20μg/dm3) and ~ 86% and ~ 87% at higher concentration (500μg/dm3), respectively, using 3g/dm3 of BFA dosage at 303K. The adsorption of arsenics on BFA-Fe was very rapid. Pseudo-second-order kinetic model well represented the adsorption kinetics of both As(III) and As(V). Error analyses functions for adsorption of As(III) and As(V) onto BFA-Fe. Based on these error analyses, R-P isotherm was found to be fitted. Thermodynamic parameters, i.e., ΔG°, ΔH°, and ΔS°, were also calculated. At 25.0 to 45.0°C, the values of ΔG° lie in the range of -43.85, -45.34, -48.82, -51.31, -53.8, and -44.75, -48.3, -51.84, -55.39, -58.93, -55.57 for As (III), and As (V) respectively, indicating that adsorption is spontaneous and exothermic in nature. Regeneration study was carried out by different solvent and thermal methods. Our results revealed that BFA-Fe can be reused directly for making fire-briquettes to explore its energy value. From this study, As containment is most effective removal from aqueous solution and mimic to any contaminated water resources.

DFT insight into Cd2+, Hg2+, Pb2+, Sn2+, As3+, Sb3+, and Cr3+ heavy metal ions adsorption onto surface of bowl-like B30 nanosheet

Contamination of water resources by heavymetal ions, is a drastic environmental concern. In this study, the interaction of Cd2+, Hg2+, Pb2+, Sn2+, As3+, Sb3+, and Cr3+ metal ions onto surface of the bowl-like B30 nanosheet was scrutinized based on density functional theory (DFT) calculations. Adsorption energy (Eads) values revealed that the As3+ interacted better with bowl-like B30 nanosheet in comparison to other metal ions, having adsorption energy values of −299.57 and −628.56 kcal mol−1in the gas phase and aqueous media, respectively. However, Hg2+, Pb2+, and Sn2+ metal ions physically adsorbed onto bowl-like B30 nanosheet in the gas phase because of their much less value of adsorption energy. The sign of adsorptionGibbs free energy change(ΔGads) and adsorption enthalpy change (ΔHads) values for all complexes was found to be negative in the gas phase and aqueous media, which indicated that the adsorption process is spontaneous and exothermic. Frontier molecular orbital (FMO) analysis exhibited a decrease in the HOMO-LUMO energy gap of studied complexes, boosting the electrical conductivity of these complexes. Natural bond orbital (NBO) analysis and charge decomposition analysis (CDA) revealed donor–acceptor charge transfer interactions in the complexes. The UV–vis results depicted that λmax was red-shifted during interactions of meal ions with bowl-like B30 nanosheet. Finally,quantum theoryof atoms in molecules (QTAIM) exhibited that the interaction between As3+ metal ion and the nanosheet is covalent in nature, while the other metal ions have predominantly electrostatic with partially covalent and non-covalent characters. The theoretical results of the study represented the feasibility of applying bowl-like B30 nanosheet to remove heavy metal ions, especially As3+ and providing information for experimental researchers to treat wastewaters.

Application of Correlation Matrix and Analysis of Variance (Anova) in Profiling Surface Water in Nembe Creek of Niger Delta, Nigeria

Water resource contamination is a major concern in several regions, especially in the Niger Delta, in which the oil exploration activities pose serious risks to human health, water resource and the environment. This present study evaluates the properties of surface water in Nembe Creek. Surface water samples were collected from three (3) control stations and twenty-four (24) sampling stations around the creek during the wet and dry seasons. The samples were subjected to analysis following the standard operating procedures of ASTM and APHA analytical methods. The relationship between the parameters and variations of surface water quality of Nembe creek were determined by using descriptive statistics, Analysis of variance (ANOVA) and Pearson correlation analysis. The results indicated pH had a mean value of 6.67± 0.33 (wet season) and 7.21 ± 0.3 (dry season), Electrical Conductivity ranged 200 – 3950 µS/cm (wet season) and 17900 – 25800 µS/cm (dry season), DO ranged between 4.3 – 5.8 (wet season) and 3.9 – 5.6 (dry season), Nitrate had values of 0.007- 0.068 mg/L (wet season) and 0 – 0.007 mg/L (dry season), Sulphate values range 130.58- 158.76 mg/L (wet season) and 215.12 – 657.35 mg/L (dry season). Iron range 3.23 – 5.6 mg/L (wet season) and 0.26 – 7.87 mg/L (dry season), Zinc ranged 0.02 – 0.47 mg/L (wet season) and 0.13 – 2.22 mg/L (dry season). Across all sampling stations and control areas during the wet season, the values for Total Petroleum Hydrocarbon (TPH), total hydrocarbon Content (THC) and Petroleum Aromatic Hydrocarbon (PAH) were below the detection limit; however, the values varied during the dry season. The Pearson Correlation matrix revealed positive, negative and significant correlations between the pairs of parameters at 95% confidence level. Amongst the sampling and control stations, some parameters had no significant difference (p &gt; 0.05), however some differences were statistically significant (p &lt; 0.05). In conclusion, Nembe Creek is marginally more polluted during the dry season than during the wet season. Most parameters on the Person's Correlation matrix were connected with each other based on the metrics. However, some parameters such as metals, do not significantly correlate with one another, indicating that the sources of contamination may have originated from various places. It is possible that the source may not predominantly originate from oil exploration activities but may involve other natural, geological and anthropogenic activities.

An Overview of Nanofiltration and Nanoadsorption Technologies to Emerging Pollutants Treatment

The presence of emerging contaminants in water resources has been a global concern due to their environmental impact and effects on human and animal health. These compounds include pharmaceuticals and personal care products, pesticides, fire retardants, hormones, and plasticizers, among others. These contaminants are not completely removed during water and wastewater conventional treatment. Thus, alternative processes are necessary to face this issue. In this context, nanotechnology represents a promising strategy for the remediation of emerging contaminants. Nanostructured materials have highlighted properties, such as adsorption capacity and porosity, chemical stability, reactivity, mobility, and antimicrobial activity. The diversity of nanomaterials and the possibility of combining them contribute to their application in contaminant mitigation. Furthermore, they can be used in different removal techniques such as adsorption, and membrane filtration. Thus, this review article provides an overview and advances in the production and application of nanofiltration membranes and adsorbent nanomaterials for the treatment of effluents containing emerging pollutants.

Nanomaterials photocatalytic activities for waste water treatment: a review.

Water is necessary for the survival of life on Earth. A wide range of pollutants has contaminated water resources in the last few decades. The presence of contaminants incredibly different dyes in waste, potable, and surface water is hazardous to environmental and human health. Different types of dyes are the principal contaminants in water that need sudden attention because of their widespread domestic and industrial use. The toxic effects of these dyes and their ability to resist traditional water treatment procedures have inspired the researcher to develop an eco-friendly method that could effectively and efficiently degrade these toxic contaminants. Here, in this review, we explored the effective and economical methods of metal-based nanomaterials photocatalytic degradation for successfully removing dyes from wastewater. This study provides a tool for protecting the environment and human health. In addition, the insights into the transformation of solar energy for photocatalytic reduction of toxic metal ions and photocatalytic degradation of dyes contaminated wastewater will open a gate for water treatment research. The mechanism of photocatalytic degradation and the parameters that affect the photocatalytic activities of various photocatalysts have also been reported.

Removal of Cr (III) from wastewater by using raw and chemically modified sawdust and corn husk

Abstract The contamination of water resources by heavy metals (HMs), mainly introduced by anthropogenic resources, has been considered as a serious environmental issue in the recent era. Therefore, the conventional methods for heavy metal removal have various drawbacks in terms of cost, toxicity, and efficiency. The novel study investigated the biosorption intensity of raw and chemically modified sawdust (SD) and corn husk (CH) to eliminate chromium (III) from the aqueous solutions. SD and CH were used as biosorbents and were treated chemically with sulfuric acid (H2SO4), sodium hydroxide (NaOH), and detergent powder. The biosorption potential was estimated based on percentage removal efficiency (% RE) of chromium (III) and the adsorption intensity (qmax). The characterization of surface morphology and functional groups of biosorbents was studied by SEM and FTIR. Moreover, the adsorption isotherm models (Langmuir and Freundlich), kinetic models (pseudo-first-order kinetics and pseudo-second-order kinetics), and thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also assessed to predict the biosorption process. The results of % RE revealed that detergent-treated SD (DTSD) and detergent-treated CH (DTCH) showed highest % RE of 9.27 ± 0.15 (%) and 99.16 ± 0.08 (%) for elimination of chromium (III), respectively. Similarly, base-treated SD (BTSD) and base-treated CH (BTCH) exhibited 95.53 ± 0.18 (%) and 92.43 ± 0.22 (%) of % RE compared with 77.87 ± 1.64 (%) and 81.96 ± 0.34 (%) removal efficiency of acid-treated SD (ATSD) and acid-treated CH (ATCH), respectively. The raw SD (RSD) and raw CH (RCH) showed lower % RE of 23.68 ± 1.52 (%) and 35.52 ± 4.74 (%) for Cr (III) removal. Further, the porosity on the biosorbent's surface and attached functional groups increased after chemical treatment and this variation resulted in increased removal efficiency after chemical treatments. The Langmuir isotherm model and the Freundlich isotherm model were employed to predict the biosorption process, and both these models are best-fitted. The pseudo-second-order kinetic model was promising representative of the biosorption data. The process was endothermic and the parameters indicated that Cr (III) biosorbtion was thermodynamically favorable. Therefore, the obtained results highlighted that detergent-treatment enhanced the % RE, and DTSD and DTCH are highly efficient biosorbents for eliminating Cr (III) from aqueous solutions. Thus, detergent-treated biosorbents are proved to be a promising sustainable, eco-friendly, and cost-effective way to treat HMs from aqueous solutions as they utilize natural agriculture waste products and also handle issues related to excessive solid waste management.

Nitrate contamination in water resources, human health risks and its remediation through adsorption: a focused review.

The level of nitrate in water has been increasing considerably all around the world due to vast application of inorganic nitrogen fertiliser and animal manure. Because of nitrate's high solubility in water, human beings are getting exposed to it mainly through various routes including water, food etc. Various regulations have been set for nitrate (45-50 mgNO3-/L) in drinking water to protect health of the infants from the methemoglobinemia, birth defects, thyroid disease, risk of specific cancers, i.e. colorectal, breast and bladder cancer caused due to nitrate poisoning. Different methods like ion exchange, adsorption, biological denitrification etc. have the ability to eliminate the nitrate from the aqueous medium. However, adsorption process got preference over the other approaches because of its simple design and satisfactory results especially with surface modified adsorbents or with mineral-based adsorbents. Different types of adsorbents have been used for this purpose; however, adsorbents derived from the biomass wastes have great adsorption capacities for nitrate such as tea waste-based adsorbents (136.43mg/g), carbon nanotube (142.86mg/g), chitosan beads (104mg/g) and cetyltrimethylammonium bromide modified rice husk (278mg/g). Therefore, a thorough literature survey has been carried out to formulate this review paper to understand various sources of nitrate pollution, route of exposure to the human beings, ill effects along with discussing the key developments as well as the new advancements reported in procuring low-cost efficient adsorbents for water purification.

MoS2-Cu/CuO@graphene Heterogeneous Photocatalysis for Enhanced Photocatalytic Degradation of MB from Water.

The industrial revolution resulted in the contamination of natural water resources. Therefore, it is necessary to save and recover the natural water resources. In this regard, polymer-based composites have attracted the scientific community for their application in wastewater treatment. Herein, molybdenum disulfide composites with a mix phase of copper, copper oxide and graphene (MoS2-Cu/CuO@GN) were synthesized through the hydrothermal method. Methylene blue (MB) was degraded by around 93.8% within the 30 min in the presence of MoS2-Cu/CuO@GN under visible light. The degradation efficiency was further enhanced to 98.5% with the addition of H2O2 as a catalyst. The photocatalytic degradation efficiency of pure MoS2, MoS2-Cu/CuO and MoS2-Cu/CuO@GN were also investigated under the same experimental conditions. The structural analysis endorses the presence of the Cu/CuO dual phase in MoS2. The charge recombination ratio and band gap of MoS2-Cu/CuO@GN were also investigated in comparison to pure MoS2 and MoS2-Cu/CuO. The chemical states, the analysis of C1s, O1s, Mo3d and Cu2p3, were also analyzed to explore the possible interaction among the present elements. The surface morphology confirms the existence of Cu/CuO and GN to MoS2.