Preparation of 8-hydroxyquinoline-type composite chelating material HQ-PHEMA/SiO2 and its adsorption behavior for heavy metal ions

BACKGROUNDAn 8-hydroxyquinoline (HQ)-type composite chelating material with high performance was designed and prepared. Monomer hydroxyethyl methacrylate (HEMA) was first grafted onto silica gel particles via surface-initiated graft-polymerization, forming grafted particles PHEMA/SiO2 with a high grafting degree. Subsequently, through the substitution reaction between 5-chloromethyl-8-hydroxyquinoline (CHQ) and the grafted macromolecules PHEMA, HQ groups were bonded onto the grafted particles, obtaining the composite chelating material HQ-PHEMA/SiO2. The chelating adsorption performance and mechanism of HQ-PHEMA/SiO2 towards Cu2+ and Ni2+ ions was studied, and the adsorption thermodynamics was investigated. RESULTSThe experimental results show that HQ-PHEMA/SiO2 possesses a strong adsorption affinity for heavy metal ions owing to the high density of the HQ group, and for Cu2+ and Ni2+ ions, the adsorption capacities were up to 63.4 mg g(-1) and 51.1 mg g(-1), respectively. The adsorption behavior fits the Langmuir model, and the adsorption enthalpy change H is positive, indicating endothermic chemisorption. The value of the entropy change S is also positive, and the higher value of |TS| suggests that the adsorption process is entropically driven. CONCLUSIONHQ-PHEMA/SiO2 is a promising material for the effective removal of heavy metal ions from water. (c) 2013 Society of Chemical Industry