Adsorption of Arsenic From Aqueous Solution Using Brown Seaweed (Sargassum Polycystum) Derived Biochar Impregnated With Iron Oxide (Fe2o3): Batch and Column Studies Modelling

Abstract

To investigate the potential of adsorption of arsenic from synthetic water, the brown seaweed (Sargassum polycystum) derived biochar impregnated with iron oxide (Fe2O3) was used. The biochar was produced through pyrolysis, at the temperature of 4000C, of brown seaweed biomass and subsequently impregnated with iron oxide (Fe2O3). The characterization results elucidate that the biochar derived from brown seaweed modified with iron oxide provides more adsorptive sites and surface functional groups for binding arsenic ions. Through the batch study, the arsenic adsorption efficiency of magnetic biochar was investigated by optimizing the influencing parameters such as pH, contact time, arsenic concentration, adsorbent dosage. The maximum arsenic adsorption efficiency was determined 96.7% under the optimized conditions of pH 6, adsorbent dosage of 100 mg, initial arsenic concentration of 0.25 mg/L and the contact time of 90 minutes). The equilibrium isotherms were also employed to analyze the adsorption equilibrium which reveals that both Langmuir and Freundlich isotherms are favorable adsorption process onto the biochar surface, while the kinetics adhered to the pseudo-second-order model, indicating that chemisorption serves as the controlling step in the adsorption mechanism. Through the analysis of breakthrough curves during the column study under controlled conditions, adsorption behavior and capacity were also explored. The results indicated that the column obtained complete saturation after 200 minutes. Furthermore, the investigation showed that the behavior of the column fit both the Adams-Bohart and the Thomas models, indicating the suitability for the large scale application. It can be concluded that these results support the possibility that iron-modified biochar made from macroalgae could be a useful tool for eliminating arsenic from water.