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 (Qmax = 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.

Preparation of a novel environmentally friendly hydrophobic deep eutectic solvent ChCl-THY and its application in removal of hexavalent chromium from aqueous solution.

A liquid-liquid extraction methodology was developed for the removal of Cr(VI) from contaminated water using a novel green hydrophobic deep eutectic solvent (DES) as an efficient sole extracting agent. The hydrophobic DES was obtained by mixing choline chloride and thymol in 1:4 molar ratio at 70°C for 10 min and was denoted as ChCl-THY(1:4). The ChCl-THY(1:4) works efficiently for removal of high (20 mg/L) and low (500 µg/L) concentration of Cr(VI) from artificially contaminated natural water with >95% extraction efficiency (E%) at optimized reaction conditions (pH 2-6, 40°C). The DES was characterized by 1 H NMR and FTIR spectroscopy, and the data suggest that interaction occurs between Cl- ion of choline chloride and H atoms of thymol molecules. Physicochemical properties such as density, melting point, moisture, and solubility were studied and discussed. Herein, no sharp melting point was observed for ChCl-THY(1:4) in DSC curve. DES was regenerated using 0.1 M NaOH as stripping agent, and 50%-60% extraction efficiency could be attained in the next cycle. A plausible mechanism of interaction between Cr(VI) species and DES was also explored with the help of FTIR spectroscopy. PRACTITIONER POINTS: A novel hydrophobic DES (ChCl-THY) is prepared by mixing choline chloride and thymol at 1:4 molar ratio. ChCl-THY(1:4) is employed for the first time as sole extracting agent to remove the Cr(VI) from contaminated aqueous solution. >95% extraction efficiency was achieved by ChCl-THY(1:4) in natural water conditions at µg/L and mg/L level of contamination. Both the component used to prepare the DES are naturally abundant; hence, DES is not toxic for biota. The element present in natural water did not show any interference with extraction of Cr(VI).