A report on arsenic removal from water via adsorption of an arsenomolybdate complex on S–CuFe2O4 adsorbents†

Drinking ground water in many areas of Pakistan is contaminated by dissolved arsenic. The consumption of arsenic-contaminated water causes many carcinogenic diseases. Hence, this work aims to estimate and eliminate arsenic from ground water used for drinking purposes in the Layyah District (Punjab – PK). For the purpose, water samples were collected from selected areas of the aforementioned district, and average arsenic concentration was estimated to be 95 ppb. Thereafter, to remove dissolved arsenic contents (As³⁺ and As⁵⁺), sulphur-doped copper ferrite, i.e., S–CuFe₂O₄ adsorbent, was developed via a hydrothermal approach. To justify its effectiveness, structural morphology of the adsorbent was evaluated via XRD, FT-IR, Raman and AFM analysis, whereas its stability was investigated via TGA analysis. Its purity and chemical compositions were determined using SEM, EDX and XPS techniques. Magnetic properties of S–CuFe₂O₄ were examined via VSM. The results indicated that spinel cubic morphology of S–CuFe₂O₄ facilitates the effective adsorption of arsenic contents. For complete elimination, arsenic contents were first converted to an arsenomolybdate complex (AMC) and then removed from water via adsorption on S–CuFe₂O₄. The adsorption was found to be spontaneous with ΔG = −13.51 kJ mol⁻¹, and adsorption kinetics for the AMC were well fitted by pseudo second order with a correlation coefficient (R²) of 0.99997. Adsorption isotherm and electrostatic interaction between S–CuFe₂O₄ and AMC were confirmed and revealed using Langmuir and Temkin models with R² = 0.97021 and R² = 0.87431, respectively. Results suggested that one gram of S–CuFe₂O₄ is enough to deliver 275 gal of arsenic free water.