The discharge of arsenic into aquatic ecosystems has become a matter of concern in India over the last few decades. Study on the arsenic removal efficiency and the underlying mechanism is of great significance in developing new remediation strategies for arsenic polluted water. Here batch experiments were carried out in combination with instrumental analysis of FTIR, SEM and TGA to investigate the effects, influential factors and mechanisms of arsenic removal from aqueous solution. Modification using polyethylenimine (PEI) for the incorporation of more amino group on the biosorbent (Zea mays cob), results into the increase in percentage sorption of As (III) and As (V) up to 80.57 and 97.45% respectively. Arsenic species have chemical affinity with the amino group. Enhancement in the sorption capacity of the Zen mays cob powder is due to the increase in the stability of the biosorbent The findings open up new avenues in the modern technology of water treatment using biosorbents, possessing potential for commercialization. (C) 2013 Elsevier B.V. All rights reserved.