Potassium fulvate-functionalized graft copolymer of polyacrylic acid from cellulose as a promising selective chelating sorbent

Abstract

Further to our previous study on the grafting polymerization of acrylic acid (AA) from cellulose (Cell) that was accomplished in presence of potassium fulvate (KF) and methylenebisacrylamide (MBA), we report that the produced bio-based graft copolymer show improved chelating activity and promising selectivity. Preliminary investigations revealed that Cu(II) uptake was much higher than that of Co(II) and Ni(II) during competitive removal from their mixture. Selective removal of Cu(II) could proceed very efficiently from the mixture during the first 5 minutes of contact with the chelating graft at pH 5.5, which is attributed to the deprotonation of the –COOH groups above their pKa. Kinetic modeling studies revealed that the second-order model was best satisfactorily approximated, which signifies the domination of the chemisorption on the uptake process. The intraparticle diffusion model confirmed this conclusion and further proved that the uptake process was mainly governed by boundary layer effect as a result of electrostatic attraction while the diffusion-controlled step was insignificant. A thermodynamic study on the competitive adsorption revealed the exothermic nature of the process with adverse effect on the adsorption at elevated temperatures with respect to Ni(II) and Co(II) but to a much lesser extent in case of Cu(II), which signifies its greater affinity.