Removal of arsenic (III and V) from aqueous solution using stable maghemite (γ -Fe2O3) loaded pumice composite

The maghemite (gamma-Fe2O3) loaded pumice composite (P-maghemite) was prepared through the chemical co-precipitation method by refluxing the Fe2+ and Fe3+ salts in an alkaline medium in presence of the base material pumice. A series of batch experiments were conducted first to study the effect of varying experimental conditions, viz contact time, pH, and initial arsenic concentration, on the removal efficiency of As(III) and As(V) by the developed composite. For both the species of arsenic, the removal was found significantly higher at lower pH and reduced precipitously after pH > 7. The adsorption process of As(III) and As(V) was well illustrated by the pseudo-second-order kinetics and Langmuir isotherm. The maximum adsorption capacity was observed as 30.36 and 33.21 mg/g of the adsorbent for As(III) and As(V), respectively. The developed composite was then assessed for its regeneration by repeated cycles of sorption and desorption with 0.1 M NaOH. Regeneration efficiency of 94.10% was observed for the developed P-maghemite after three cycles of (de)-sorption. A long term continuous column experiment was then conducted with arsenic laden aqueous water using a 20 cm uniformly packed vertical column having an inner diameter of 4.5 cm. More than 99% removal of arsenic was observed using the 30 days breakthrough curves (BTCs), which corresponds to the 0.76 mg/g of arsenic adsorption on the developed adsorbent. The findings of this study ascertain that the developed composite, P-maghemite, presents a great removal potential of arsenic in mixed and continuous flow systems.

Automated summary

The study successfully developed a composite material loaded on maghemite through the chemical co-precipitation method, showing great potential in removing arsenic from water. The adsorption efficiency was higher at lower pH values, showcasing promising results for the removal of both As(III) and As(V) by the developed composite.