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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. Refereed/Peer-reviewed

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 fol-lowed 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 heat-ing 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 effi-cient 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. (c) 2022 Elsevier Inc. All rights reserved. Refereed/Peer-reviewed

Green synthesis of nanoparticles is becoming increasingly popular as a simple and environmentally friendly method. In this study, iron-based nanoparticles (Fe-NPs) were successfully prepared using a peanut skin extract, where the peanut skin as an agricultural waste product was easy to obtain in large quantities, relatively inexpensive and also environmentally friendly. The average particle size of the produced Fe-NPs changed with their post-synthesis drying conditions. Under vacuum drying at 60 ⁰C, the smallest average particle size obtained was 10.6 nm. The synthesized Fe-NPs had a core shell-like structure, inwhich the core was composed of Fe⁰, and the shell was a layered coating composed of biomolecules(e.g. anthocyanins, flavonols, phenolic compounds, epicatechin), iron oxides, Fe coordination compounds and iron-carbon alloys. Thereafter Fe-NPs (2 g L⁻¹) prepared under different drying conditions were evaluated for their ability to remove Cr(VI) from aqueous solutions at pH of 4.7 and 25 ⁰C. Fe-NPs obtained under vacuum drying at 60 ⁰C performed the best, removing 100% of Cr(VI), from a 10 mg L⁻¹ aqueous solution of Cr(VI) in just one min. Desorption and reuse experiments show that the desorption rate of Cr using 16 M hydrochloric acid and the recycling rate reached 70.2 and 59.9%, respectively. A potential mechanism for Fe NP synthesis involving the formation of intermediate complexes, an electron transfer reaction and adsorption of non-reducing organic macromolecules at the solid-liquid interfaces was proposed. Refereed/Peer-reviewed

Refereed/Peer-reviewed As one of the important contaminants in wastewater, Pb(II) becomes a severe public health problem because of its non-biodegradable and persistent nature. In this study, reduced graphene oxide (RGO) prepared using green tea extract was successfully used to remove Pb(II) from aqueous solutions. A 96.6% of Pb(Il) was removed at 10 mg/L Pb(II) and 0.4 g/L RGO with pH 4.5 at 30 degrees C, and the adsorption of Pb(II) by RGO followed pseudo-second-order kinetics. To confirm the removal mechanism, various methods (Transmission Electron Microscopy, Raman spectroscopy and X-ray diffraction) were used to characterize RGO before and after Pb(II) adsorption. The results showed that the surface of RGO after Pb(II) adsorption became rougher, and the interlayer spacing increased from 0.36 nm to 0.40 nm, indicating that Pb(II) was adsorbed on the surface and between the layers of RGO. Finally, the adsorption mechanism of Pb(II) by RGO was proposed, Pb(Il) was adsorbed on the surface of RGO via the electrons on the it-bond on RGO and the interaction of Pb(II) with oxygen-containing functional groups, which were supported by the Fourier Transform Infrared and X-ray photoelectron spectroscopy results. (C) 2019 Elsevier Inc. All rights reserved.

Organopalygorskites were synthesised by using dimethyldioctadecylammonium bromide (DMDOA) and cetylpyridinium chloride (CP) with surfactant loadings equivalent to 100% and 200% CEC of the palygorskite. The four organopalygorskites, thus produced, were characterised by Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and zeta potential measurement. FTIR and TGA data demonstrated that higher surfactant loadings as well as long branched chain DMDOA produced highly ordered surfactant conformation. SEM morphological results showed that the organopalygorskites had less entangled fibres than the unmodified palygorskite. The zeta potential values showed positive charge formation on the organopalygorskites surface when they were synthesised with surfactant loadings equivalent to 200% CEC of the palygorskite. The organopalygorskites were tested for adsorption of p-nitrophenol (PNP) with a special focus on the adsorption isotherms. The adsorption data could be fitted with multiple isothermal models indicating that the adsorption was controlled by multiple mechanisms. Sorbent loading rate, initial pH, temperature and ionic strength might all affect the adsorption process. Also, DMDOA modified organopalygorskites reduced desorption/redispersal of adsorbed PNP back into the environment to a great extent. This study will be helpful in designing palygorskite-based organoclay adsorbents for remediating organic environmental contaminants which are ionic in nature. Refereed/Peer-reviewed