Analysis of breakthrough developments and modeling of fixed bed adsorption system for As(V) removal from water by modified calcined bauxite (MCB)

The feasibility of As(V) removal from aqueous environment by a fixed bed of the adsorbent, modified calcined bauxite (MCB), in a continuous flow system has been investigated. The response of the adsorbent bed under various operating conditions of bed depth, flow rate and influent concentration were examined. The various column parameters including adsorption rate, adsorption capacity and depth of exchange zone were evaluated using the Bohart and Adams adsorption model. MCB exhibited an adsorption capacity of 627.3 mg/l with an adsorption rate constant 0.9925 l/mg h at an influent As(V) concentration of 2 mg/l. A minimum adsorbent depth of 1.3 cm is enough to produce effluent with As(V) concentration less than 0.01 mg/l from an influent of 2 mg/l, in a 20 mm diameter MCB column. The service time of adsorbent beds under different flow rate and influent concentration were predicted using the bed depth service time (BDST) model and are compared with experimental observations. The observed data on service time and breakthrough curve correlated well with the theoretical values. The breakthrough curves of MCB obtained by experimental observations under different flow rates were compared with those developed by mass transfer model using Langmuir isotherm data. In the continuous flow system, MCB is found to have As(V) scavenging potential of 0.470 mg of As(V)/g.