Physically-crosslinked activated CaCO3/polyaniline-polypyrrole-modified GO/alginate hydrogel sorbent with highly efficient removal of copper(II) from aqueous solution

Herein, alginate-based porous nanocomposite hydrogel (CPGA) was produced using alginate as entrapment agent, polyaniline-polypyrrole-modified graphene oxide (GPP) as functional filler, and CaCO3 as pore-former for enhanced Cu(II) removal from water. Synergism among tri-components help to 3D network formation and Cu(II) removal. The parameters of components, solution pH, contact time, adsorbate concentration, temperature, coexisting substances and dosage were investigated in batch sorption mode. Spontaneous and endothermal adsorption process of Cu(II) by CPGA followed pseudo-second-order model and Freundlich model with experimental maximum adsorption capacity of 291.2 mg/g, which was better than most of reported alginate-based sorbents. CPGA showed good anti-interference ability in the presence of NaCl and humic acid as well as in actual Cu(II)-polluted lake water. In the multi-ions system, little sorption loss was observed for Pb(II), Cu(II) and Cd(II) capture, and even strengthened Cr(VI) removal relative to those in the single system. Furtherly, minor discrepancy (< 10%) was noted after eight successive adsorption-desorption cycles. FTIR and XPS revealed that reactive N-/O-containing groups was mainly responsible for Cu(II) removal; the residual CaCO3 acted the role of pH-buffer and provided refresh binding sites for the gel. This work could expand the potential applicability of alginate-based sorbents for heavy metal removal from water.