Poly(acrylic acid/acrylamide/sodium humate) superabsorbent hydrogels for metal ion/dye adsorption: Effect of sodium humate concentration

摘要

A series of novel superabsorbent hydrogels based on acrylic acid (AAc), acrylamide (AM), and sodium humate (SH) were prepared by free-radical solution copolymerization for removal of dye and metal ion from waste water. Ammonium per sulfate was used as initiator and N,N' methylene bisacrylamide as crosslinker. The hydrogels were characterized with the help of FTIR and SEM. In this study the concentration of SH was varied in the range of 0.50-4.76 wt based on total monomer content and the resulting hydrogels were investigated for the effect of SH on swelling and diffusion kinetic parameters such as equilibrium swelling ratio, initial swelling rate, swelling rate constant, maximum swelling at equilibrium, and type of diffusion, etc. Hydrogel having 2.43 wt SH content showed the maximum water absorbency of 724 g of water per gram of hydrogel. Swelling exponent found in the range 0.68-0.79 thus suggesting Non-Fickian diffusion mechanism. The swelling behavior was also studied in different concentrations of salt solutions sodium chloride (NaCl), magnesium chloride (MgCl _2), and ferric chloride (FeCl _3). The synthesized superabsorbent hydrogels were used for the adsorption of Cu ~(2+) ions and methylene blue (MB) dye from their aqueous solutions. The influence of SH concentration on the Cu ~(2+) ions and MB molecules binding capacity of hydrogels was tested. The chelation behavior was modeled using Langmuir isotherm. The maximum binding capacity for Cu ~(2+) ion was 299 mg/L at 1000 mg/L, initial Cu ~(2+) ion concentration and 269 mg/L at 320 mg/L, initial MB dye molecules concentration per gm of AAc/AM/SH containing 2.43 wt SH content.