Geogenic arsenic removal through core-shell based functionalized nanoparticles: Groundwater in-situ treatment perspective in the post-COVID anthropocene

Removal of As(III)/As(V) from aqueous solution using newly developed thiosalicylic acid coated magnetite [TSA@Fe3O4] nanoparticles

The aim of this study was to develop an affordable adsorption methodology for removal of As(III)/As(V) from contaminated water. Herein, novel adsorbent TSA@Fe₃O₄ nanoparticles (NPs) were synthesized by decorating thiosalicylic acid (TSA) on magnetite nanoparticles (Fe₃O₄ NPs) and employed for removal of As(III)/As(V) species from artificially contaminated natural water systems. TSA@Fe₃O₄ NPs demonstrated excellent adsorption efficiency (AE) and 98% of As(V) and 93% of As(III) was removed at optimized experimental conditions. The adsorption kinetic and equilibrium isotherm studies were conducted preferentially for As(III) adsorption. Adsorption followed the pseudo-second-order kinetic (R² = 99%) and adsorption data fitted well in Langmuir isotherm model (R² = 99%) and maximum adsorption capacity (Q_max = 34.1 mg/g) was calculated for 5 mg/L of As(III) by using 10 mg of TSA@Fe₃O₄ NPs. The effect of pH, contact time, adsorption dosages, and competitive anions was also examined to identify optimum experimental conditions. The adsorbent was characterized by advanced instrumental techniques to investigate the physicochemical properties and stability of NPs. To comprehend the interactions of As(III) species with adsorbent NPs, NPs were analyzed using XPS and Raman spectroscopy techniques. Both the techniques confirmed that As(III) and As(V) species present simultaneously on adsorbent surface. The TSA@Fe₃O₄ was regenerated using 0.1 M NaOH. The findings of this study suggested that TSA@Fe₃O₄ NPs could be considered a potential adsorbent for effective remediation of As(III) and As(V) from contaminated natural water systems.

Recent developments of magnetic nanoadsorbents for remediation of arsenic from aqueous stream

One of the emerging environmental concerns is the high levels of arsenic ions found in groundwater and other water sources. Decontaminating water that contains arsenic is crucial for environmental and health reasons. Nano-adsorbents have gained much interest recently for the adsorptive removal of arsenic species from wastewater. On the other hand, for their prospective use in natural water treatment, current nano-adsorbents must be separated from treated fluids. Researchers studied nanocomposite iron oxide-based adsorbents to overcome these problems and to design effective sorbents for removing arsenic. This study provides a summary of current developments in the field of magnetic nanoadsorbents for the removal of various arsenic compounds from wastewater. Adsorption of arsenic from groundwater has been found to be very promising for magnetic nanoadsorbents. In order to eliminate arsenic from the aqueous phase, magnetic nanocomposite adsorbents may offer practical and affordable water purification solutions.

Polyaniline/Glauconite Nanocomposite Adsorbent for Congo Red Dye from Textile Wastewater

Glauconite (Gl), a naturally occurring clay material, was utilized as an affordable and ecologically friendly adsorbent to explore its capturing capacity towards Congo red (CR) dye from textile industrial waste effluent. To improve adsorption and removal effectiveness, a modification technique utilizing polyaniline (PAN) was investigated. An X-ray diffractometer (XRD), a scanning electron microscope (SEM), and Fourier transformer infrared (FTI-R) were applied as strong familiar characterization techniques for all used adsorbents. The effects of starting concentration, contact duration, adsorbent dose, pH, and temperature on the adsorption process were also studied. The reusability of the adsorbent was studied over four adsorption cycles. The results show that PAN modification of Gl enhances the effectiveness of CR elimination. The clearance efficiency of raw and modified glauconite at 25 °C and pH 7 was 77% and 91%, respectively. The kinetics and isotherms of Congo red dye adsorption were investigated using batch studies to determine the impacts of various experimental conditions. The maximum adsorption capacity of the glauconite/polyaniline (Gl/PAN) nanocomposite rose from 11.9 mg/g for Gl to 14.1 mg/g in accordance with the isotherm analysis, which shows that the Langmuir isotherm properly characterizes the experimental data. The pseudo-second-order model (R2 = 0.998) properly expresses the experimental data. The reusability research proved that the adsorbents may be reused effectively. The overall results suggest that the modified Gl by PAN might be used as a low-cost, natural adsorbent for eliminating CR color from textile effluent.

Magnetic nanocomposite adsorbents for abatement of arsenic species from water and wastewater

The presence of high concentrations of arsenic species in drinking water and other water bodies has become one of the most critical environmental concerns. Therefore, decontamination of arsenic-containing water is essential for improved health and environmental concern. In recent years, nano-adsorbents have been widely used for the adsorptive removal of arsenic from water. Separating existing nano-adsorbents from treated waters, on the other hand, is a critical issue for their potential applications in natural water treatment. To address these issues and to effectively remove arsenic from water, researchers looked at iron oxide-based magnetic nanocomposite adsorbents. The magnetic nanoadsorbents have the benefit of surface functionalization, making it easier to target a specific pollutant for adsorption, and magnetic separation. In addition, magnetic nanoparticles have a large surface area, high chemical inertness, superparamagnetic, high magnetic susceptibility, small particle size, and large specific surface area, and are especially easily separated in a magnetic field. Magnetic nano-adsorbents have been discovered to have a lot of potential for eliminating arsenic from water. The recent advances in magnetic nano-absorbents for the cleanup of arsenic species from water are summarized in this paper. Future perspectives and directions were also discussed in this article. This will help budding researchers for the further advancement of magnetic nanocomposites for the treatment of water and wastewater contaminated with arsenic.

Aminoalkyl-organo-silane treated sand for the adsorptive removal of arsenic from the groundwater: Immobilizing the mobilized geogenic contaminants

Arsenic (As), a geogenic legacy pollutant can be present in environmental matrices (water, soil, plants, or animal) in two redox states (As(III) or As(V)). In the present study, charged mono- and di-amino functionalized triethoxy and methoxyorganosilane (TT1 and TT2- 1% and 5%) were impregnated with quartz sand particles for the treatment of As polluted water. Spectroscopic characterization of organosilane treated sand (STS) indicated the co-existence of minerals (Mg, Mn, Ti), amide, and amidoalkyl groups, which implies the suitability of silanized materials as a metal(loids) immobilization agent from water. Changes in peaks were observed after As sorption in Fourier thermal infrared and EDS images indicating the involvement of chemisorption. Batch sorption studies were performed with the optimized experimental parameters, where an increased removal (>20% for TT2-1% and >60% for TT1-1%) of As was observed with sorbate concentration (50 µg L^-1), temp. (25 ± 2 ºC) and sorbent dosages (of 10 g L^-1) at 120 min contact time. Among the different adsorbent dosages, 10 g L^-1 of both TT1 and TT2 was selected as an optimum dosage (maximum adsorption capacity ≈ 2.91 μg g^-1). The sorption model parameters suggested the possibility of chemisorption, charge/ion-dipole interaction for the removal of arsenate.

Removal of Arsenic by Wheat Straw Biochar from Soil

Biochar prepared from wheat straw (Triticum aestivum) at different pyrolysis temperatures was screened, followed by its application to soil for arsenic removal in the present study. Characterization of biochar by Field emission scanning electron microscope studies and Fourier thermal Infrared imaging showed smooth and porous biochar surface and abundance of surface functional groups. A low value of H/C was obtained by CHNS analyzer, indicating high stability of biochar. The surface area was 15.86 m²/g on an average. Batch sorption experiments were carried out to optimize conditions for arsenic sorption. Maximum arsenic removal of 83.7% was obtained when applied at a 7.5% dose for a contact time of 60 min at 25 °C. Isotherm, kinetic and thermodynamic studies revealed the feasibility of sorption and removal of arsenic through physisorption, chemisorption, ion exchange, and diffusion.

Differentiating Nanomaghemite and Nanomagnetite and Discussing Their Importance in Arsenic and Lead Removal from Contaminated Effluents: A Critical Review

Arsenic and lead heavy metals are polluting agents still present in water bodies, including surface (lake, river) and underground waters; consequently, the development of new adsorbents is necessary to uptake these metals with high efficiency, quick and clean removal procedures. Magnetic nanoparticles, prepared with iron-oxides, are excellent candidates to achieve this goal due to their ecofriendly features, high catalytic response, specific surface area, and pulling magnetic response that favors an easy removal. In particular, nanomagnetite and maghemite are often found as the core and primary materials regarding magnetic nanoadsorbents. However, these phases show interesting distinct physical properties (especially in their surface magnetic properties) but are not often studied regarding correlations between the surface properties and adsorption applications, for instance. Thus, in this review, we summarize the main characteristics of the co-precipitation and thermal decomposition methods used to prepare the nano-iron-oxides, being the co-precipitation method most promising for scaling up processes. We specifically highlight the main differences between both nano-oxide species based on conventional techniques, such as X-ray diffraction, zero and in-field Mössbauer spectroscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism, the latter two techniques performed with synchrotron light. Therefore, we classify the most recent magnetic nanoadsorbents found in the literature for arsenic and lead removal, discussing in detail their advantages and limitations based on various physicochemical parameters, such as temperature, competitive and coexisting ion effects, i.e., considering the simultaneous adsorption removal (heavy metal-heavy metal competition and heavy metal-organic removal), initial concentration, magnetic adsorbent dose, adsorption mechanism based on pH and zeta potential, and real water adsorption experiments. We also discuss the regeneration/recycling properties, after-adsorption physicochemical properties, and the cost evaluation of these magnetic nanoadsorbents, which are important issues, but less discussed in the literature.

Effect of Mg2+ ions on competitive metal ions adsorption/desorption on magnesium ferrite: Mechanism, reusability and stability studies

The adsorption behavior of magnesium ferrite in single- and multicomponent metal ions solutions in the presence of Mg²⁺ ions were studied. A dramatic decrease in the adsorption capacity of magnesium ferrite towards Mn²⁺, Co²⁺, and Ni²⁺ ions for comparison study of single- and multicomponent solutions was established. The affinity of the sorbent in accordance with the maximum sorption capacities increases in the following order Cu²⁺ > Co²⁺ > Ni²⁺ > Mn²⁺. High efficiency of magnesium ferrite regeneration (~100%) with aqueous solutions of magnesium chloride in the concentration range of 0.001-0.1 M was shown. The low degree of toxic metal ions desorption combined with XRD, IR spectroscopy, and EDX analysis data indicate the key role of Mg²⁺ ion adsorption in the magnesium ferrite adsorbent regeneration. The positive effect of the introduction of Mg²⁺ ions into multicomponent solutions on metal ions adsorption was established, which is accompanied by an increase in the maximum sorption capacity for all metal ions and especially significant increase in the selectivity towards Cu²⁺ ions (2.41 mmol/g). The stability of the crystal structure of magnesium ferrite and a low degree of Mg²⁺ and Fe³⁺ ions leaching during multiple cycles of adsorption and regeneration of the adsorbent were observed.

Physico-Chemical Parameters and Health Risk Analysis of Groundwater Quality

Groundwater pollution is a very common problem worldwide, as it poses a serious threat to both the environment and the economic and social development and consequently generates several types of costs. The analysis of pollution control involves a permanent comparison between pollution costs and the costs associated with various methods of pollution reduction. An environmental policy based on economic instruments is more effective than an environmental policy focused on command and control tools. In this respect, the present paper provides a case study showing how anthropogenic factors such as wastewater, industrial, agricultural, and natural factors are able to change the physical and chemical parameters of groundwater in the study area, thus endangering their quality. In order to monitor the groundwater quality in the region of Dobrudja, an analysis of physico-chemical parameters was performed. The content of heavy metals was analyzed and the health risk index was taken into account and analyzed, in order to set a better correctness of the metal content from the underground waters. Studies on groundwater quality control have shown that, in many parts of the world, water has different degrees of quality depending on the natural and anthropogenic factors acting on the pertaining environment. This is why more attention should be paid to the prevention of groundwater pollution and the immediate remediation of accidents.

Hexametaphosphate cross-linked chitosan beads for the eco-efficient removal of organic dyes: Tackling water quality

There is an increasing trend of developing various low-cost grafted natural amino polysaccharides for the biosorptive removal of noxious dye effluents like Malachite green (MG) and anionic Reactive Red-195 (RR-195) dyes from aqueous solution. Chemically cross-linked chitosan microsphere (CTS-HMP), a promising non-toxic biosorbent possessing high charge density and thermal stability was prepared by using hexametaphosphate as ionic cross-linker. Batch biosorption experiments were carried out under different temperatures (298, 308 and 318 K), pH (2.0-10.0), initial concentrations (25-250 mg L^-1), adsorbent dosage (0.01-0.1 g) and contact times (0-180 min) to understand the optimum experimental conditions and simultaneously evaluate the adsorption isotherms and kinetics of CTS-HMP. Biosorption equilibrium was established in 120 and 60 min for MG and RR-195 removal process. The pseudo-equilibrium process was best described by the pseudo-second-order kinetic (R² ≥ 0.98), Freundlich and Temkin isotherm model (R² ≥ 0.90). The removal rate of MG and RR-195 gradually increased (69.40 and 148 mg g^-1) at 250 mg L^-1 of initial concentration till 100 and 50 min of contact period in a single contaminant system, though the removal efficiency of acid dye was ~2 times higher compared to basic dye under optimum conditions (p < 0.05; t-test). Thermodynamic parameters indicated exothermic (MG) and endothermic (RR-195) nature of spontaneous dye removal. The activation energy of sorption (E_a) was <50 kJ mol^-1 which highlighted the importance of physical adsorption process. Therefore, the obtained results clearly validate the sustainable utilization of CTS-HMP as a promising functionalized chitosan microparticles/agent for removing dye effluents from the contaminated aqueous phase.

The latest strategies in the fight against the COVID-19 pandemic: the role of metal and metal oxide nanoparticles

In this review, we summarize and highlight the latest achievements based on nanoparticles in the fight against COVID-19.