Adsorptive characteristics in a system consisting of iron-coated sands, arsenic and humic acid

Iron oxide-coated sand (IOCS) was used as an adsorbent for removing As(V) from water in which the adsorption capabilities of IOCS for As(V) were examined under different environmental conditions. A synthetic water sample was used to study the impact of humic acid (HA) on the adsorption capabilities of IOCS for As(V). Results showed that the adsorptive characteristics of IOCS on As(V) fairly obey the pseudo-second order kinetic adsorption behavior. In addition, the adsorption mechanisms of IOCS for As(V) appeared to be governed by the physical and chemical adsorption. HA plays an essential role in competitive adsorption with As(V) on IOCS surface. The adsorption capacities of IOCS for As(V) under different environmental conditions are ranked in terms of magnitude as follows: single As(V) adsorption system > As(V)/HA + IOCS adsorption system > HA/IOCS + As(V) adsorption system. Langmuir adsorption isotherm regression results show that at 25 °C and pH = 3.0, the maximum adsorption capacities of IOCS for As(V), As(V)/HA + IOCS and -1 HA/IOCS + As(V) are 1,667, 1,000 and 714 ig As g IOCS, respectively.