Study on polyacrylamide/attapulgite adsorbent composite

Using solution polymerization, polyacrylamide/attapulgite (PAM/ATP) adsorbent was synthesized by grafting acrylamide (AM) onto the silane coupling reagent modified ATP (OATP). The preparing conditions of the PAM/ATP were investigated, and the analyses by TG/DSC and FT-IR were conducted to characterize the synthesized PAM/ATP. The results show that the prepared PAM/ATP gives a maximum Hg²⁺ adsorption capacity of 135.5 mg·g^-1 under following conditions: AM mass concentration of 30.0% (relative to OATP mass, the same hereinafter), reaction time of 6 h, initiator dosage of 3.0% (weight) and reaction temperature of 80°C. TG/DSC analyses reveal that the DSC curve of the PAM/ATP exhibits an endothermic peak of organic decomposition at 345°C, and in the temperature range of 280°C to 600°C, the weight loss of the PAM/ATP (18.0%) is much more than those of the ATP (5.0%) and the OATP (7.0%). The FT-IR spectra show that the new absorption bands at 1604 cm^-1 (-NH₂ or-NH bending vibration), 3190 cm^-1 (-NH₂ or-NH stretching vibration) and 1671 cm^-1 (-C=O stretching vibration) appear on the spectrum of PAM/ATP; It indicates that the PAM is successfully grafted onto the surface of OATP. It was found that the Hg²⁺ adsorption capacity of the PAM/ATP prepared under the above conditions is more than 6 folds compared with those of the ATP and OATP.