Conservation agriculture works as a catalyst for sustainable sodic soil reclamation and enhances crop productivity and input use efficiency: A scientific inquiry.

Soil sodicity is a growing concern for crop growth and development in arid and semi-arid regions of the world. Conservation agriculture (CA) provides an effective solution towards reclamation of degraded sodic lands and enhance the crop productivity. A field experiment was carried out to assess the sodic soil reclamation potential of CA based management practices including zero tillage, legume (mungbean; Mb) rotation, residue (+R) mulch, and subsurface drip irrigation (SDI) for three years under rice-wheat (RW) system. The system scenarios (Sc) comprised of multiple indicators to measure their impact on soil properties as well as system productivity, profitability, water and nitrogen use efficiency. The results indicated that soil pHs under Sc5-Sc8 (CA-based SDI scenarios) was significantly (p < 0.05) lowered by 2.16, 2.16 and 1.33% compare with mean of Sc1 and Sc2 (CT-based system; 9.10, 8.29 and 8.14) at all three soil layers (0-5, 5-15 and 15-30 cm), respectively. Similarly, the exchangeable sodium percentage (ESP) was lowered by 2.9, 11.2 and 14.9% under CA-based scenarios with residue management compared with CT-based system (mean of Sc1 and Sc2; 15.2, 17.2 and 28.6%) during the study. The concentration of extractable anions (COЗ2‾, HCOЗ‾, Cl‾) decreased notably whereas, soil organic carbon and soil solution cations (Na+, Ca2+, Mg2+) concentration were increased under CA based management SDI plots. In addition, CA with SDI scenarios (mean of Sc5-Sc8) proved to be more productive and water-efficient than CA-based flood irrigation (FI; mean of Sc3 and Sc4). Moreover, CA-based FI and SDI scenarios saved 29.5 and 60.7% irrigation water, and improved the partial factor productivity of nitrogen (PFPN) by 6.8 and 24.4%, respectively compared to CT-R (conventional tillage without residue) based Sc1. Therefore, CA practices can potentially reduce sodicity and improve soil chemical properties for profitable crop cultivation.

Effects of microplastics on soil microorganisms and microbial functions in nutrients and carbon cycling - A review.

The harmful effects of microplastics (MPs) pollution in the soil ecosystem have drawn global attention in recent years. This paper critically reviews the effects of MPs on soil microbial diversity and functions in relation to nutrients and carbon cycling. Reports suggested that both plastisphere (MP-microbe consortium) and MP-contaminated soils had distinct and lower microbial diversity than that of non-contaminated soils. Alteration in soil physicochemical properties and microbial interactions within the plastisphere facilitated the enrichment of plastic-degrading microorganisms, including those involved in carbon (C) and nutrient cycling. MPs conferred a significant increase in the relative abundance of soil nitrogen (N)-fixing and phosphorus (P)-solubilizing bacteria, while decreased the abundance of soil nitrifiers and ammonia oxidisers. Depending on soil types, MPs increased bioavailable N and P contents and nitrous oxide emission in some instances. Furthermore, MPs regulated soil microbial functional activities owing to the combined toxicity of organic and inorganic contaminants derived from MPs and contaminants frequently encountered in the soil environment. However, a thorough understanding of the interactions among soil microorganisms, MPs and other contaminants still needs to develop. Since currently available reports are mostly based on short-term laboratory experiments, field investigations are needed to assess the long-term impact of MPs (at environmentally relevant concentration) on soil microorganisms and their functions under different soil types and agro-climatic conditions.

Ecological and human health risk assessment of pharmaceutical compounds in the Sirsa River of Indian Himalayas.

The Baddi-Barotiwala-Nalagarh (BBN) region of Indian Himalayas is one of the most important pharmaceutical industrial clusters in Asia. This study investigated the distribution, and ecological and human health risks of four most frequently used pharmaceuticals [ciprofloxacin (CIP), norfloxacin (NOR), cetirizine (CTZ) and citalopram oxalate (ECP)] when co-occurring with metal ions in the Sirsa river water of the BBN region. The concentration range of the selected pharmaceuticals was between 'not detected' to 50 µgL-1 with some exception for CIP (50-100 µgL-1) and CTZ (100-150 µgL-1) in locations directly receiving wastewater discharges. A significant correlation was found between the occurrences of NOR and Al (r2 = 0.65; p = 0.01), and CTZ and K (r2 = 0.50; p = 0.01) and Mg (r2 = 0.50; p = 0.01). A high-level ecological risk [risk quotient (RQ) > 1] was observed for algae from all the pharmaceuticals. A medium-level risk (RQ = 0.01-0.1) was observed for Daphnia from CIP, NOR and ECP, and a high-level risk from CTZ. A low-level risk was observed for fishes from CIP and NOR, whereas CTZ and ECP posed a high-level risk to fishes. The overall risk to ecological receptors was in the order: CTZ > CIP > ECP > NOR. Samples from the river locations receiving water from municipal drains or situated near landfill and pharmaceutical factories exhibited RQ > 1 for all pharmaceuticals. The average hazard quotient (HQ) values for the compounds followed the order: CTZ (0.18) > ECP (0.15) > NOR (0.001) > CIP (0.0003) for children (0-6 years); ECP (0.49) > CTZ (0.29) > NOR (0.005) > CIP (0.001) for children (7-17 years), and ECP (0.34) > CTZ (0.21) > NOR (0.007) > CIP (0.001) for adults (>17 years). The calculated risk values did not readily confirm the status of water as safe or unsafe because the values of predicted no-effect concentration (PNEC) would depend on various other environmental factors such as quality of the toxicity data, and species sensitivity and distribution, which warrants further research.

Characterization of flue gas desulphurized (FGD) gypsum of a coal-fired plant and its relevant risk of associated potential toxic elements in sodic soil reclamation.

Thermal Power Plant generates FGD gypsum as by-product during coal combustion. This study evaluates the characterization (spectroscopic and elemental), potentially toxic elements (PTEs) distribution, and environmental risk assessment of FGD gypsum for safe and sustainable use in agriculture. The XRD and SEM analysis confirmed the dominance of crystalline CaSO4·2H2O in FGD gypsum. The order of concentrations of PTEs in FGD gypsum was Fe > Al > Mn > Zn > Ni > Co. The residual fraction was the dominant pool, sharing 80-90% of the total PTEs. The heavy metals (HMs) were below the toxic range in the leachates. The Co, Ni, Al, Fe Mn, Zn had low (< 10%) risk assessment code and the ecotoxicity was in the range of 0.0-7.46%. The contamination factor was also low (0.0-0.16) at the normal recommended doses of FGD gypsum application for sodicity reclamation. The enrichment factor was in the order of Al < Mn < Co < Zn < Ni. Mn [enrichment factor (Ef) 1.2-2.0] and Co (Ef 1.7-2.8) showed negligible enrichment of metals, whereas Ni (Ef 4.3-5.2) and Zn (Ef 4.5-5.6) reported moderate accumulation in soil. The application of FGD gypsum @ 10 t ha-1 for sodicity reclamation will develop a geo-accumulation index below the critical values indicating its safe and sustainable use to achieve land degradation neutrality (LDN) and UN's Sustainable Development Goals.

Restoring soil quality and carbon sequestration potential of waterlogged saline land using subsurface drainage technology to achieve land degradation neutrality in India.

Subsurface drainage (SSD) has been proved to be an effective technology to reclaim waterlogged saline soils. Three SSD projects were implemented in Haryana, India in 2009, 2012 and 2016 to study the long term effect of SSD (10, 7 and 3 years) operation on restoring productivity and carbon sequestration potential of degraded waterlogged saline soils under prevalent rice-wheat cropping system. These studies indicated that successful operation of SSD improved soil quality parameters such as bulk density, BD (from 1.58 to 1.52 Mg m-3), saturated hydraulic conductivity, SHC (from 3.19 to 5.07 cm day-1); electrical conductivity, ECe (from 9.72 to 2.18 dS m-1), soil organic carbon, OC (from 0.22 to 0.34 %), dehydrogenase activity, DHA (from 15.44 to 31.65 µg g-1 24 h-1), and alkaline phosphatase, ALPA (from 16.66 to 40.11 µg P-NP g-1 h-1) in upper soil surface (0-30 cm). The improved soil quality resulted in increased rice-wheat system yield (rice equivalent yield) by 328 %, 465 % and 665 % at Kahni, Siwana Mal and Jagsi sites, respectively. Studies also revealed that carbon sequestration potential of degraded land increased with the implementation of SSD projects. The principal component analysis (PCA) showed that % OC, ECe, ALPA, available N and K content were the most contributing factor for soil quality index (SQI). The overall result of the studies showed that SSD technology holds great potential to improve soil quality, increase crop productivity, farmers' income and ensure land degradation neutrality and food security in waterlogged saline areas of western Indo Gangetic Plain of India. Hence, it can be concluded that large scale adoption of SSD may fulfill the promise "No poverty, Zero hunger, and Life on land" sustainable development goals of United Nation in degraded waterlogged saline areas.

Synthesis and characterization of PCN-222 metal organic framework and its application for removing perfluorooctane sulfonate from water.

Poly- and perfluoro alkyl substances (PFAS) are a group of man-made, notoriously persistent, and highly toxic contaminants in the environment reported worldwide. Many adsorbents including granular activated carbon, graphene, biochar, zeolites, and clay minerals have been tested for PFAS removal from water, but most of these materials suffer from high cost and/or poor removal performance. Here, we synthesized, characterized, and examined the efficiency of PCN-222(Fe), a new porous metal organic framework (MOF) with high water stability, for adsorptive removal of a frequently occurring PFAS, perfluorooctane sulfonate (PFOS), from water. The adsorption isotherm and kinetic studies revealed high PFOS adsorption capacity of PCN-222 (2257 mg/g), with rapid PFOS removal rate (within 30 min). The structure of PCN-222 was unaffected in water in the pH range of 2-10 but disintegrated and lost its PFOS removal ability at pH > 10. The PFOS adsorption on PCN-222 was an endothermic reaction. Electrostatic attraction was a dominant mechanism for PFOS adsorption at < 1694 mg/g PFOS concentration, while hydrophobic interaction accompanied with hydrogen-bonding was responsible at ≥ 1694 mg/g PFOS concentration. The interlayer morphology of PCN-222 did not change due to increasing PFOS loading. The findings of this study demonstrated superior features of PCN-222 over other conventional adsorbents for its potential application in removing PFOS from contaminated water to reduce PFOS transfer from water to living organisms.

Nanocomposite-based smart fertilizers: A boon to agricultural and environmental sustainability.

Fertilizers are indispensable agri-inputs to accomplish the growing food demand. The injudicious use of conventional fertilizer products has resulted in several environmental and human health complications. To mitigate these problems, nanocomposite-based fertilizers are viable alternative options. Nanocomposites, a novel class of materials having improved mechanical strength, barrier properties, and mechanical and thermal stability, are suitable candidates to develop eco-friendly slow/controlled release fertilizer formulations. In this review, the use of different nanocomposite materials developed for nutrient management in agriculture has been summarized with a major focus on their synthesis and characterization techniques, and application aspects in plant nutrition, along with addressing constraints and future opportunities of this domain. Further detailed studies on nanocomposite-based fertilizers are required to evaluate the cost-effective synthesis methods, in-depth field efficacy, environmental fate, stability, etc. before commercialization in the field of agriculture. The present review is expected to help the policy makers and all the stakeholders in the large-scale commercialization and application of nanocomposite-based smart fertilizer products with greater societal acceptance and environmental sustainability in near future.

A mechanistic insight into the shrinkage and swelling of Ca-montmorillonite upon adsorption of chain-like ranitidine in an aqueous system.

Adsorption behavior of ranitidine hydrochloride (RT) on a Ca-montmorillonite (SAz-1) was studied in aqueous system through batch experiments. The adsorption kinetics revealed that the equilibrium reached within 0.25 h and the data fitted well to the pseudo-second order kinetic equation (R2 = 0.98). The maximum RT adsorption capacity of SAz-1 was 369.2 mg/g and the adsorption isotherm data followed the Langmuir model (R2 = 0.99). The adsorption of RT and desorption of exchangeable cations from the clay mineral were linearly correlated, suggesting that cation exchange was the dominant mechanism of RT adsorption. The XRD examination of RT-adsorbed SAz-1 samples (unsaturated/saturated) after heating enabled the calculation of RT occupied area in the interlayer of the clay mineral. The results suggested that adsorbed-RT at low loading rate could lay on the internal surfaces in a free style to reduce the basal spacing (d001 value) of SAz-1. When the RT loading rate was increased, a limited surface space enforced more RT molecules to lay in a tilted style and caused interlayer swelling of SAz-1 increasing the d001 value. The trend of rising decomposition temperature of RT with increasing RT loading rates confirmed intercalation of RT molecules in SAz-1. Infrared spectral analysis revealed the participation of amide and furan groups of RT in binding between RT and SAz-1. Thus, this study indicated that SAz-1 is an efficient adsorbent to remove RT from contaminated water, and the chain-like molecular structure of RT could cause an irregular change in the basal spacing of swelling type clay minerals.

Nano Minerals Applications in Pollutants Removal: A New Open Special Issue in Materials.

'Nano Minerals Applications in Pollutants Removal: A New Open Special Issue in Materials', aims to publish high-quality research and review articles on the basic and applied science of clay mineralogy and make great contributions to the understanding of applied mineralogy in removing pollutants from aqueous and soil environments [...].

Designer biochar with enhanced functionality for efficient removal of radioactive cesium and strontium from water.

Radioactive elements released into the environment by accidental discharge constitute serious health hazards to humans and other organisms. In this study, three gasified biochars prepared from feedstock mixtures of wood, chicken manure, and food waste, and a KOH-activated biochar (40% food waste + 60% wood biochar (WFWK)) were used to remove cesium (Cs+) and strontium (Sr2+) ions from water. The physicochemical properties of the biochars before and after adsorbing Cs+ and Sr2+ were determined using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, extended X-Ray absorption fine structure (EXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX). The WFWK exhibited the highest adsorption capacity for Cs+ (62.7 mg/g) and Sr2+ (43.0 mg/g) among the biochars tested herein. The removal of radioactive 137Cs and 90Sr exceeded 80% and 47%, respectively, in the presence of competing ions like Na+ and Ca2+. The functional groups present in biochar, including -OH, -NH2, and -COOH, facilitated the adsorption of Cs+ and Sr2+. The Cs K-edge EXAFS spectra revealed that a single coordination shell was assigned to the Cs-O bonding at 3.11 Å, corresponding to an outer-sphere complex formed between Cs and the biochar. The designer biochar WFWK may be used as an effective adsorbent to treat radioactive 137Cs- and 90Sr-contaminated water generated during the operation of nuclear power plants and/or unintentional release, owing to the enrichment effect of the functional groups in biochar via alkaline activation.

Biochar-microorganism interactions for organic pollutant remediation: Challenges and perspectives.

Numerous harmful chemicals are introduced every year in the environment through anthropogenic and geological activities raising global concerns of their ecotoxicological effects and decontamination strategies. Biochar technology has been recognized as an important pillar for recycling of biomass, contributing to the carbon capture and bioenergy industries, and remediation of contaminated soil, sediments and water. This paper aims to critically review the application potential of biochar with a special focus on the synergistic and antagonistic effects on contaminant-degrading microorganisms in single and mixed-contaminated systems. Owing to the high specific surface area, porous structure, and compatible surface chemistry, biochar can support the proliferation and activity of contaminant-degrading microorganisms. A combination of biochar and microorganisms to remove a variety of contaminants has gained popularity in recent years alongside traditional chemical and physical remediation technologies. The microbial compatibility of biochar can be improved by optimizing the surface parameters so that toxic pollutant release is minimized, biofilm formation is encouraged, and microbial populations are enhanced. Biocompatible biochar thus shows potential in the bioremediation of organic contaminants by harboring microbial populations, releasing contaminant-degrading enzymes, and protecting beneficial microorganisms from immediate toxicity of surrounding contaminants. This review recommends that biochar-microorganism co-deployment holds a great potential for the removal of contaminants thereby reducing the risk of organic contaminants to human and environmental health.

Novel MOF-808 metal-organic framework as highly efficient adsorbent of perfluorooctane sulfonate in water.

Perfluorooctane sulfonate (PFOS) is a highly persistent contaminant of emerging concern causing harmful effects to human and ecosystem health. In this study, a novel MOF-808 metal-organic framework (MOF) was prepared and evaluated for adsorptive removal of PFOS from aqueous solution. The MOF-808 had high specific surface area (SSA; 1610 m2/g) and was structurally stable in aqueous medium for 7 days under different pH conditions. The MOF-808 reached PFOS adsorption equilibrium within 30 min (at 500 mg/L initial PFOS) and attained the maximum adsorption capacity of 939 mg/g at pH 4.1 - 5.4 (with 50 - 500 mg/L initial PFOS). The PFOS adsorption capacity of MOF-808 was unaffected at pH 2 to 7, but gradually decreased at pH > 7. High SSA, favorable pore size and abundant active adsorption sites on MOF-808 triggered high PFOS adsorption onto the adsorbent. The PFOS adsorption process was endothermic and spontaneous in nature. Electrostatic interaction between the cationic central cluster ([Zr6O4(OH)4]12+) of MOF-808 and PFOS anion was identified as the key mechanism of PFOS adsorption onto MOF-808, as evident from the infrared spectroscopic investigation of the adsorbent. This study suggests that MOF-808 can be considered as a highly efficient adsorbent for PFOS removal from water and warrants future research to evaluate the application and performance of the material under wastewater conditions.

Facile one pot preparation of magnetic chitosan-palygorskite nanocomposite for efficient removal of lead from water.

Development of polymeric magnetic adsorbents is a promising approach to obtain efficient treatment of contaminated water. However, the synthesis of magnetic composites involving multiple components frequently involves tedious preparation steps. In the present study, a magnetic chitosan-palygorskite (MCP) nanocomposite was prepared through a straight-forward one pot synthesis approach to evaluate its lead (Pb2+) removal capacity from aqueous solution. The nano-architectural and physicochemical properties of the newly-developed MCP composite were described via micro- and nano-morphological analyses, and crystallinity, surface porosity and magnetic susceptibility measurements. The MCP nanocomposite was capable to remove up to 58.5 mg Pb2+ g-1 of MCP from water with a good agreement of experimental data to the Langmuir isotherm model (R2 = 0.98). The Pb2+ adsorption process on MCP was a multistep diffusion-controlled phenomenon evidenced by the well-fitting of kinetic adsorption data to the intra-particle diffusion model (R2 = 0.96). Thermodynamic analysis suggested that the adsorption process at low Pb2+ concentration was controlled by chemisorption, whereas that at high Pb2+ concentration was dominated by physical adsorption. X-ray photoelectron and Fourier transform infrared spectroscopy results suggested that the Pb adsorption on MCP was governed by surface complexation and chemical reduction mechanisms. During regeneration, the MCP retained 82% Pb2+ adsorption capacity following four adsorption-desorption cycles with ease to recover the adsorbent using its strong magnetic property. These findings highlight the enhanced structural properties of the easily-prepared nanocomposite which holds outstanding potential to be used as an inexpensive and green adsorbent for remediating Pb2+ contaminated water.

Challenges and opportunities in sustainable management of microplastics and nanoplastics in the environment.

The accumulation of microplastics (MPs) and nanoplastics (NPs) in terrestrial and aquatic ecosystems has raised concerns because of their adverse effects on ecosystem functions and human health. Plastic waste management has become a universal problem in recent years. Hence, sustainable plastic waste management techniques are vital for achieving the United Nations Sustainable Development Goals. Although many reviews have focused on the occurrence and impact of micro- and nanoplastics (MNPs), there has been limited focus on the management of MNPs. This review first summarizes the ecotoxicological impacts of plastic waste sources and issues related to the sustainable management of MNPs in the environment. This paper then critically evaluates possible approaches for incorporating plastics into the circular economy in order to cope with the problem of plastics. Pollution associated with MNPs can be tackled through source reduction, incorporation of plastics into the circular economy, and suitable waste management. Appropriate infrastructure development, waste valorization, and economically sound plastic waste management techniques and viable alternatives are essential for reducing MNPs in the environment. Policymakers must pay more attention to this critical issue and implement appropriate environmental regulations to achieve environmental sustainability.

Natural and engineered clays and clay minerals for the removal of poly- and perfluoroalkyl substances from water: State-of-the-art and future perspectives.

Poly- and perfluoroalkyl substances (PFAS) present globally in drinking-, waste-, and groundwater sources are contaminants of emerging concern due to their long-term environmental persistence and toxicity to organisms, including humans. Here we review PFAS occurrence, behavior, and toxicity in various water sources, and critically discuss their removal via mineral adsorbents, including natural aluminosilicate clay minerals, oxidic clays (Al, Fe, and Si oxides), organoclay minerals, and clay-polymer and clay­carbon (biochar and graphene oxide) composite materials. Among the many remediation technologies, such as reverse osmosis, adsorption, advanced oxidation and biologically active processes, adsorption is the most suitable for PFAS removal in aquatic systems. Treatment strategies using clay minerals and oxidic clays are inexpensive, eco-friendly, and efficient for bulk PFAS removal due to their high surface areas, porosity, and high loading capacity. A comparison of partition coefficient values calculated from extracted data in published literature indicate that organically-modified clay minerals are the best-performing adsorbent for PFAS removal. In this review, we scrutinize the corresponding plausible mechanisms, factors, and challenges affecting the PFAS removal processes, demonstrating that modified clay minerals (e.g., surfactant, amine), including some commercially available products (e.g., FLUORO-SORB®, RemBind®, matCARE™), show good efficacy in PFAS remediation in contaminated media under field conditions. Finally, we propose future research to focus on the challenges of using clay-based adsorbents for PFAS removal from contaminated water due to the regeneration and safe-disposal of spent clay adsorbents is still a major issue, whilst enhancing the PFAS removal efficiency should be an ongoing scientific effort.

The role of soils in the disposition, sequestration and decontamination of environmental contaminants.

Soil serves as both a 'source' and 'sink' for contaminants. As a source, contaminants are derived from both 'geogenic' and 'anthropogenic' origins. Typically, while some of the inorganic contaminants including potentially toxic elements are derived from geogenic origin (e.g. arsenic and selenium) through weathering of parent materials, the majority of organic (e.g. pesticides and microplastics) as well as inorganic (e.g. lead, cadmium) contaminants are derived from anthropogenic origin. As a sink, soil plays a critical role in the transformation of these contaminants and their subsequent transfer to environmental compartments, including groundwater (e.g. pesticides), surface water (phosphate and nitrate), ocean (e.g. microplastics) and atmosphere (e.g. nitrous oxide emission). A complex transformation process of contaminants in soil involving adsorption, precipitation, redox reactions and biodegradation control the mobility, bioavailability and environmental toxicity of these contaminants. Soil also plays a major role in the decontamination of contaminants, and the 'cleaning' action of soil is controlled primarily by the physico-chemical interactions of contaminants with various soil components, and the biochemical transformations facilitated by soil microorganisms. In this article, we examine the geogenic and anthropogenic sources of contaminants reaching the soil, and discuss the role of soil in the sequestration and decontamination of contaminants in relation to various physico-chemical and microbial transformation reactions of contaminants with various soil components. Finally, we propose future actions that would help to maintain the role of soils in protecting the environment from contaminants and delivering sustainable development goals. This article is part of the theme issue 'The role of soils in delivering Nature's Contributions to People'.

Distribution, behaviour, bioavailability and remediation of poly- and per-fluoroalkyl substances (PFAS) in solid biowastes and biowaste-treated soil.

Aqueous film-forming foam, used in firefighting, and biowastes, including biosolids, animal and poultry manures, and composts, provide a major source of poly- and perfluoroalkyl substances (PFAS) input to soil. Large amounts of biowastes are added to soil as a source of nutrients and carbon. They also are added as soil amendments to improve soil health and crop productivity. Plant uptake of PFAS through soil application of biowastes is a pathway for animal and human exposure to PFAS. The complexity of PFAS mixtures, and their chemical and thermal stability, make remediation of PFAS in both solid and aqueous matrices challenging. Remediation of PFAS in biowastes, as well as soils treated with these biowastes, can be achieved through preventing and decreasing the concentration of PFAS in biowaste sources (i.e., prevention through source control), mobilization of PFAS in contaminated soil and subsequent removal through leaching (i.e., soil washing) and plant uptake (i.e., phytoremediation), sorption of PFAS, thereby decreasing their mobility and bioavailability (i.e., immobilization), and complete removal through thermal and chemical oxidation (i.e., destruction). In this review, the distribution, bioavailability, and remediation of PFAS in soil receiving solid biowastes, which include biosolids, composts, and manure, are presented.

Unravelling the mechanism of amitriptyline removal from water by natural montmorillonite through batch adsorption, molecular simulation and adsorbent characterization studies.

Amitriptyline (AMI) is one of the most common tricyclic antidepressant personal care medications. Due to its environmental persistence and bioaccumulation, release of AMI into the environment via wastewater streams in elevated levels could lead to significant ecological and human health impacts. In this study, the adsorption of AMI by montmorillonite (SWy-2), a naturally abundant smectite clay with sodium ions as the main interlayer cations, was investigated. Maximum AMI adsorption (276 mg/g) occurred at pH 7-8. After adsorption, examination of the adsorbent's X-ray diffraction pattern indicated that interlayer expansion had occurred, where chemical stoichiometry confirmed cation exchange as the principal adsorption mechanism. AMI adsorption reached equilibrium within 4 h, with kinetic data best fitting the pseudo-second order kinetic model (R2 = 0.98). AMI adsorption was unaffected by solution pH in the range 2-11, where adsorption was endothermic, and molecular simulations substantiated by Fourier transform infrared spectroscopy and thermogravimetric investigations indicated that the orientation of AMI molecules in the interlayer was via an amine group and a benzene ring. Overall this research shows that SWy-2 has significant potential as a low cost, effective, and geologically derived natural material for AMI removal in wastewater systems.

Fe(III) loaded chitosan-biochar composite fibers for the removal of phosphate from water.

Excess phosphorous (P) in aquatic systems causes adverse environmental impacts including eutrophication. This study fabricated Fe(III) loaded chitosan-biochar composite fibers (FBC-N and FBC-C) from paper mill sludge biochar produced under N2 (BC-N) and CO2 (BC-C) conditions at 600 °C for adsorptive removal of phosphate from water. Investigations using SEM/EDX, XPS, Raman spectroscopy, and specific surface area measurement revealed the morphological and physico-chemical characteristics of the adsorbent. The Freundlich isotherm model well described the phosphate adsorption on BC-N, while the Redlich-Peterson model best fitted the data of three other adsorbents. The maximum adsorption capacities were 9.63, 8.56, 16.43, and 19.24 mg P g-1 for BC-N, BC-C, FBC-N, and FBC-C, respectively, indicating better adsorption by Fe(III) loaded chitosan-biochar composite fibers (FBCs) than pristine biochars. The pseudo-first-order kinetic model suitably explained the phosphate adsorption on BC-C and BC-N, while data of FBC-N and FBC-C followed the pseudo-second-order and Elovich model, respectively. Molecular level observations of the P K-edge XANES spectra confirmed that phosphate associated with iron (Fe) minerals (Fe-P) were the primary species in all the adsorbents. This study suggests that FBCs hold high potential as inexpensive and green adsorbents for remediating phosphate in contaminated water, and encourage resource recovery via bio-based management of hazardous waste.

Soil salinity under climate change: Challenges for sustainable agriculture and food security.

Soil salinity is one of the major and widespread challenges in the recent era that hinders global food security and environmental sustainability. Worsening the situation, the harmful impacts of climate change accelerate the development of soil salinity, potentially spreading the problem in the near future to currently unaffected regions. This paper aims to synthesise information from published literature about the extent, development mechanisms, and current mitigation strategies for tackling soil salinity, highlighting the opportunities and challenges under climate change situations. Mitigation approaches such as application of amendments, cultivation of tolerant genotypes, suitable irrigation, drainage and land use strategies, conservation agriculture, phytoremediation, and bioremediation techniques have successfully tackled the soil salinity issue, and offered associated benefits of soil carbon sequestration, and conservation and recycling of natural resources. These management practices further improve the socio-economic conditions of the rural farming community in salt-affected areas. We also discuss emerging reclamation strategies such as saline aquaculture integrated with sub surface drainage, tolerant microorganisms integrated with tolerant plant genotypes, integrated agro-farming systems that warrant future research attention to restore the agricultural sustainability and global food security under climate change scenarios.