Clay-biochar composite for arsenic removal from aqueous media

Arsenic is present mainly in groundwater in the forms of highly toxic arsenate and arsenite. Biochar has been a promising cost effective and carbon negative material for many different contaminants such as trace metals, antibiotics, pesticides etc., however, not for anionic metalloids as arsenic. This study intended to evaluate the potential of a novel composite prepared using biochar, derives from fibrous fraction of municipal solid waste in Gohagoda landfill site, Kandy, Sri Lanka and red earth clay for remediate As(III) in aqueous media. Pyrolyzed biochar+red earth composite was characterized for its physicochemical properties. Furthermore, As(III) pH dependency (pH 3–9), kinetics behavior and sorbate (50–1000 µg L⁻¹) concentrations were investigated using a batch sorption technique. The concentrations of As(III) in aqueous media were measured by inductively coupled plasma optical emission spectrometry. For arsenic (III), pH 6–7 range was favorable for adsorption process. Whereas, highest adsorption at 24 hours reaction time at pH 6–7 recorded as around 25% (12.5 µg g⁻¹) for arsenic (III). Moreover, well fitted pseudo second order (R² = 0.928) could suggest chemical adsorption mechanism rather than a physical adsorption mechanism in to the adsorbent. Hence, process involved with chemisorption can be suggested as the As(III) removal mechanism. However, further isotherm experiments are needed with expanded concentration range to mechanism identification.