Design and synthesis of a dual-purpose superadsorbent containing a high density of chelating motifs for the fast mitigation of methylene blue and Pb(II)

Maleic acid underwent alternate copolymerization with diallylaminomethylphosphonic acid·HCl [(CH2=CHCH2)2NH+CH2PO3H2 Cl-] and a cross-linker to give a new pH-responsive resin. Methylene blue (MB) removal from its 3000 ppm solution by the resin at pH 7 followed second-order kinetics with an Ea of 34.8 kJ mol-1. MB removal was achieved very fast (10 min), attaining over 98.5% at 328 K. The qe obtained using MB concentrations in the range 100-8000 ppm fitted the Langmuir nonlinear isotherm model to give ΔG°, ΔH°, and ΔS° values of ≈ -21 kJ, 36.5 kJ mol-1, and 185 J mol-1 K-1, respectively. The resin is a superadsorbent with a qmax value of 2445 mg g-1. The adsorbent also removed 97% Pb(II) within 5 min from its 10 000 ppb solution. The resin reduced the Pb(II) concentration from 200 to 3.8 ppb. The resin also demonstrated its ability to remove contaminants from industrial wastewater, reducing priority metal contaminants to ppb and sub-ppb levels. The resin can be recycled with stable efficiency. The outstanding performance places the resin in a top position in a list of recently reported sorbents.