Removal of heavy metal ions from aqueous solution by anionic polyacrylamide-based monolith: equilibrium, kinetic and thermodynamic studies

In the present study, a macroporous polyacrylamide-based monolith bearing negatively charged sulfonic acid groups was synthesized as a new adsorbent for the removal of heavy metals ions (Pb2+, Cd2+, and Cr3+) from aqueous solutions. Vinylsulfonic acid was selected as an anionic monomer to introduce a negative charge on the surface of the resulting monolith that forms a complex with investigated metal ions. The influences of solution pH, contact time, monolith dosage, initial concentration, and temperature on Pb2+, Cd2+, and Cr3+ removal were determined using the batch equilibrium technique. Adsorption data were modeled with Langmuir, Freundlich, and Dubinin-Raduskevich isotherm models. The experimental equilibrium data for Pb2+, Cd2+, and Cr3+ using the synthesized monolith showed a good correlation with the Langmuir isotherm model. Based on the Langmuir model, the maximum monolayer adsorption capacities of the monolith were 22.8 mg g(-1) for Cd2+, 33.3 mg g(-1) for Pb2+, and 66.7 mg g(-1) for Cr3+ at 25 degrees C. Kinetic studies revealed that the adsorption of the metal ions onto the monolith followed pseudo-second-order kinetics. The negative and positive values of free energy (Delta G degrees) and enthalpy (Delta H degrees) revealed that the adsorption of the metal ions onto the monolith was spontaneous and endothermic, respectively.

Automated summary

A new macroporous polyacrylamide-based monolith with negatively charged sulfonic acid groups was synthesized as an adsorbent for removing heavy metal ions from aqueous solutions. The adsorption data fit well with the Langmuir isotherm model.