A Cellulose/Bentonite Grafted Polyacrylic Acid Hydrogel for Highly-Efficient Removal of Cd(Ii)

Abstract

In order to remove Cd(II) from waste water, a high-performance hydrogel named microcrystalline cellulose/bentonite grafted polyacrylic acid (MCC/Ben-g-PAA) was synthesized using microcrystalline cellulose (MCC) and bentonite (Ben) as raw materials with ammonium persulfate (APS) as the initiators and N,N'-methylenebisacrylamide (MBA) acting as crosslinker. The adsorbent was characterized by SEM, FTIR, XPS, TG and the results showed that the adsorbent contains many C and O adsorption groups, which is beneficial for the adsorption of Cd(II). The results of the batch adsorption experiments showed that the adsorption of Cd(II) could peak at 242.53 mg/g in the optimum conditions with the dosage at 1 g/L and pH at 6. Besides, the kinetics fitted the pseudo-second order dynamics, and the isotherm followed the Freundlich model, indicating that the adsorption of Cd(II) was a chemisorption-based multi-layer process and mainly controlled by intraparticle diffusion. Ion-competition experiments showed that the adsorbent was highly selective with a removal rate of 96.72% for Cd(II). Regeneration cycle experiments showed that the adsorbent maintained 88.37% Cd(II) removal rate after 10 cycles. Therefore, MCC/Ben-g-PAA is a highly efficient, selective and reproducible adsorbent and proves a very promising and efficient adsorbent for the treatment of wastewater.

Keywords: Cellulose hydrogel, Bentonite, Cd(II) adsorption