Effectively removal of cationic and anionic dyes by pH-sensitive amphoteric adsorbent derived from agricultural waste-wheat straw

An amphoteric adsorbent (MCA/WS-g-PDMAEMA) derived from the agricultural waste-wheat straw (WS) was successfully synthesized and characterized, its adsorption capacities towards the cationic (methylene blue, MB) and anionic (orange II, ORII and methyl orange, MO) dyes in the single and binary systems were evaluated. The results showed that the adsorption abilities of MCA/WS-g-PDMAEMA towards ORII with pH-sensitive enhanced significantly, and the maximum adsorption capacities was up to 506 mg g(-1) at pH2. In the cationic/anionic dyes binary systems (MB/MO and MB/ORII), the selective adsorption properties towards anionic dyes (ORII and MO) effectively enhanced and that of cationic dye inhibited at the acid condition, while contrary results were obtained at the alkaline condition. The pseudo-second-order kinetic model fitted better with the experimental data, and the possible main adsorption interaction attributed on ionic attraction was also proposed. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.