Removal and recovery of cationic dyes from aqueous solutions using spherical sulfonic lignin adsorbent

A novel spherical sulfonic lignin adsorbent, denoted as SSLA, was adopted to removal and recover the cationic dyes from aqueous solutions, e.g., Cationic Red GTL, Cationic Turquoise GB, and Cationic Yellow X-5GL, and various affecting factors were optimized. It was found that the adsorption of cationic dyes on the adsorbent was initially concentration- and temperature-dependent, and followed both the Freundlich and Langmuir isothermal adsorption. The positives values for AH indicated that the process was enclothermic. The breakthrough adsorption capacities for GTL, GB, and X-5GL were 536.0, 550.0, and 582.0 mg/g, respectively, which prevailed over the commercial powdered activated carbon and strongly acidic cation-exchange resin R732 evidently. Additionally, the maximum recovery percentage could reach 93.2, 97.1, and 96.5% separately for GTL, GB, and X-5GL, when a mixture of 3.0 mol/L HCl and alcohol with the volume ratio of 1: 4 was adopted as eluant. Moreover, the results of the mobile desorption and recovery tests indicated that the maximum concentrations of GTL, GB, and X-5GL in the eluants, could reach 13,108, 13,980, and 13,520 mg/L, respectively. Only 6.3, 5.0, and 4.6% of adsorption capacities for GTL, GB, and X-5GL decreases individually after 20 replicates of adsorption and desorption. (c) 2006 Wiley Periodicals, Inc.