Pb(II) Adsorption from Water onto Polyacrylic Acid / Chestnut Shell Pigment Hydrogel

The synthetic hydrogel with chestnut shell pigment and polyacrylic acid for lead removal from aqueous solutions. The effects of the amount of chestnut shell pigment in the synthesis process, solution pH, initial Pb(II) concentration, and adsorption time on the adsorption of hydrogel for Pb(II) were analyzed. The adsorption kinetics and adsorption isotherm were investigated. The findings revealed that the best ratio of chestnut shell pigment∶ acrylic acid was = 0.128 g/g at which the Pb(II)adsorption capacity on the as-synthesized hydrogel was 1.263 times that of the hydrogel without chestnut shell pigment. The hydrogel had a three-dimensional network structure with a pH point of zero charges of 4.2. Amino, carboxyl, and hydroxyl groups were the Pb(II)-binding sites. The suitable solution pH for the adsorption was 5.6. The adsorption process reached equilibrium within 120 min. The kinetic data conformed to the pseudo-second-order model, suggesting that chemical adsorption was the rate-limiting step. The adsorption equilibrium followed the Langmuir isothermal model with the maximum single-layer adsorption capacity of 315.6 mg/g. The results suggest that the hydrogel of polyacrylic acid/chestnut shell pigment is an excellent adsorbent with great application potential for Pb(II) removal.