Abstract
In order to avoid the secondary pollution of the toxic residue of chemical crosslinking agent accompanied by chemical hydrogel adsorbent and enhance the adsorption performance of physical hydrogel, chitosan/calcium alginate/bentonite (CTS/CA/BT) composite physical hydrogel was constructed. The formation mechanism and structure of the composite hydrogel were determined by FTIR, XRD and SEM. Adsorption performances of the hydrogel toward Pb2+, Cu2+ and Cd2+ in water under different condition as well as multi-ion competitive sorption were investigated. The adsorption processes were described with the canonical adsorption kinetics and isotherms models. With the utilization of XPS analysis and adsorption thermodynamics analysis, it was found that the adsorptions were spontaneous physico-chemical adsorptions. The results showed that the maximum adsorption capacity of the hydrogel for Pb2+, Cu2+ and Cd2+ reached up to 434.89, 115.30 and 102.38 mg·g−1, respectively, better than those of other physical hydrogels or chitosan/bentonite composite. Moreover, the composite hydrogel improved the collectability of bentonite and showed a good reusability. The modification of bentonite and the formation of hydrogel were completed simultaneously, which greatly simplifies the operation process compared with the prior similar works. These suggest that the CTS/CA/BT composite hydrogel has promising application prospects for removal of heavy metal ions from water.
Highlights
With the rapid growth of industry, significant increase of discharged heavy metal pollutants has led to numbers of environmental problems [1]
Calcium carbonate decomposed into calcium ions which crosslinked with α-L-guluronic on sodium alginate to form another network [13]
Bentonite was evenly dispersed in the cross-linked network, efficiently increasing the mechanical strength of the hydrogel, forming a chitosan/calcium alginate/bentonite composite physical hydrogel
Summary
With the rapid growth of industry, significant increase of discharged heavy metal pollutants has led to numbers of environmental problems [1]. With a three-dimensional cross-linked network, hydrogels have been widely used in the removal of heavy metal pollutants due to their rich surface functional groups and excellent water absorption performance [7]. Most of the currently developed hydrogel adsorbents inevitably use toxic chemical crosslinking agents for cross-linking [8,9,10]. These toxic reagents remaining in the hydrogel are difficult to be completely removed, causing secondary pollution and various adverse effects and burdens on the environment. The development of eco-friendly hydrogel adsorbents with prominent adsorption performance is of great significance to the remediation of heavy metal pollutants
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
