Removal of Dimethyl Arsenic Acid from Aqueous Solution by Ferric Manganese Binary Oxide

This study addresses the environmental concern of organic-arsenic pollution resulting from the discharge of dimethyl arsenic acid (DMA) through non-point sources into surface and groundwater, posing severe health risks. While efforts have primarily focused on eliminating inorganic arsenic, the toxicity of organic arsenic, particularly DMA, has been over-disregarded and necessitates a thorough examination. In response, this research focuses on developing effective adsorbents for the removal of organic arsenic, with a specific emphasis on DMA. Using the co-precipitation method, ferric manganese binary oxide (FMBO) was synthesized and compared with manganese dioxide (MnO 2 ) and ferric oxide (FeOOH). The produced adsorbents were evaluated using a range of characterization methods, such as X-ray powder diffraction (XRD), specific surface area ( S BET ), zeta (ζ)-potential, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX), and Fourier transform infrared spectroscopy (FTIR). The impact of pH, adsorption kinetics, and adsorption isotherms were investigated in batch studies to ascertain efficacy. The Elovich model, which suggests heterosphere diffusion reactions, best explained the adsorption data, according to the results followed by the pseudo-second-order model. pH had a major impact on DMA adsorption; at pH 4.0, FMBO showed a maximum adsorption capacity of 665.28 μg/g, which was higher than that of FeOOH (581.32 μg/g) and MnO 2 (510.56 μg/g). Fitting descriptions of DMA adsorption onto FMBO, FeOOH, and MnO 2 were provided by the Langmuir and Sips models. Systematic characterization by FTIR and SEM–EDX highlighted FMBO’s predominant role in DMA adsorption at lower pH. Regeneration experiments demonstrated a slight decrease in DMA adsorption from 99.04 to 94.90% after five consecutive cycles, affirming FMBO’s substantial capability to remove DMA from aqueous solutions. This study underscores the potential of FMBO as an efficient adsorbent for combating organic-arsenic pollution.