Influence of pH on arsenic(III) removal by fly ash

The objective of this study was to compare arsenic(III) removal at natural pH (pH 10.5) with that at high alkaline (pH 12.2). Experiments were carried out using fly ash from burning brown coal and biomass from the power plant (Zgierz, Poland). Experimental data were well described by the Langmuir and the pseudo-second-order chemisorption models. The maximum adsorption capacity was 19.04 and 42.73 mg/g at pH 10.5 and 12.2, respectively. It can be explained by the fact that a phase CaAsO2OH is formed at highly alkaline pH. The value of thermodynamic parameters revealed that arsenic(III) adsorption is a spontaneous and endothermic process.