Chemically modified maize cobs waste with enhanced adsorption properties upon methyl orange and arsenic

The surface chemistry of maize naturasorbent was altered in this work by the modifying agents: phosphoric acid and different amines (triethanolamine, diethylenetriamine and 1,4-diaminobutane). Removal of methyl orange (25 mg l−1) was <50% by maize corn cobs modified by phosphorylation and higher by the quaternized samples: 68% with the 1,4-diaminobutane and 73% with the diethylenetriamine modificators. Adsorption of arsenite by the samples modified with phosphoric acid/ammonia was 11 μg g−1, which corresponds to 98% removal from a 550 μg As l−1 solution for an adsorbent dose of 50 mg ml−1. The samples modified by phosphoric acid/urea removed 0.4 μg g−1 arsenate from a 300 μg As l−1 solution. Adsorption of methyl orange, arsenite and arsenate was superior by the chemically modified maize cobs judged against the initial naturasorbent. For comparison, removal by the commercial anion exchanger was 100% for methyl orange, 45% (5 μg g−1) for arsenite and 99% (5 μg g−1) for arsenate.