Water pollution caused by arsenic, which is harmful to man and living organisms, is one of a major problems faced by many countries. Due to this scenario, development of new methods and sorbents for arsenic removal from water has been the subject of intense research lately. Zeolites have been used to sorb many metal cations but show no affinity for anions due to their permanent negative charges on their crystalline aluminosilicate surface. In this work modification of zeolite P was performed by exchanged of its sodium with cerium, in which the latter has strong affinity towards arsenate (As(V)) anion. The resulting cerium-exchanged zeolite P, (CeZP) was subsequently used to sorb As(V) from aqueous solution. Parameters such as pH, initial As(V) concentration, temperature, kinetics and effect of foreign ions were investigated.

Maximum sorption of As(V) by CeZP occurred at pH range 3 to 6 at room temperature. In addition, the sorption capacity increased with increasing initial As(V) concentrations. The sorption follows Langmuir model with maximum sorption capacity of 8.72 mg g^-1 at 25 °C and increased to 23.42 mg g^-1 at 90 °C, indicating an endothermic process. This is confirmed by the positive values of sorption enthalpy, +22.25 kJmol^-1. The sorption process was found to be spontaneous with free energy value of -10.51 kJmol^-1. A positive entropy change for sorption of As(V) ion on CeZP could be due to fixation of the ions on the Ce(IV) that was randomly distributed on the zeolite P. Kinetics study shows that the As(V) sorption follows pseudo second order kinetic with rate constant of 1.14x10^-3 g mg^-1min^-1. The arsenic sorption by CeZP was not affected by the present carbonate, chloride, sulphate, bromide and nitrate but was reduced significantly in the presence of phosphate. This study shows that the as prepared CeZP was found effective for the removal of arsenic ion from wastewater sample of wood treatment industry.

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