Adsorption Properties of Cationic Polyacrylamide Modified Bentonite for Indigo Blue

Many kinds of treatment methods are used to deal with the dye wastewater,since it is difficult to be purified.The absorption processing technology is a common-used method.A cationic polyacrylamide(CPAM) modified bentonite was used as the sorbent to remove the indigo blue.The characteristics of the modified bentonite were investigated including the adsorbent dosage,pH,temperature,adsorption time and concentration of indigo blue.The results showed that the removal rate of indigo blue increased with the accretion of modified bentonite.The optimum dosage of CPAM bentonite was 3 g/L and the sorption reached equilibrium after 40 minutes.When the pH of solution ranged from 4.0 to 10.0,the variation of the adsorption capacity of CPAM bentonite with varied pH was negligible,and the maximal adsorption capacity could be kept stable.However,when the pH was higher than 10.0,the adsorption capacity significantly decreased.The adsorption process followed with the pseudo-first-order kinetics.The isothermal data of sorption followed the Langmuir and Freundlich models with regression coefficients higher than 0.99.The maximum adsorption capacity of the sorbent was 5287.0 mg/g at a pH of 6.0,which was 21.4 times of the unmodified one.The measurement of specific surface area and the characterization of the CPAM modified bentonite by FTIR and TEM analysis suggested that the structure and properties of CPAM modified bentonite were superior to the unmodified one.The ion exchange reaction between cationic polyacrylamide and sodium base bentonite contributed much on the increase of hydrophobicity and outer specific surface area.The interlayer structure of modified bentonite was also changed during this process.These variations can effectively promote the adsorptive property of modified bentonite.