RECOVERY OF CHROMIUM(Ⅲ) FROM CHROME TANNING WASTEWATER BY PRECIPITATION AND ADSORPTION PROCESSES

摘要

The study was conducted regarding the recovery of chromium(Ⅲ) from chrome tanning wastewater by precipitation and adsorption processes. The adsorption was conducted with a spherical sulfonic lignin adsorbent, denoted as SSLA and the factors affecting the precipitation and adsorption as well as desorption were comprehensively discussed. The recovery reached 91.6% by applying 12.0g/L of sodium hydroxide as precipitant, 25mg/L of cationic polyacrylamide as flocculant and 3.0g/g Cr of H_2SO_4 as solution medium. The adsorption of chromium(Ⅲ) from the supernatant liquid with SSLA has been found to be initially pH andconcentration dependent aided by higher adsorption temperature which helps to improve the adsorption capacity of SSLA. The breakthrough adsorption capacity of SSLA is 63.5mg/g, and the saturated adsorption capacity is 76.3mg/g. Moreover, the chromium(Ⅲ) adsorbed on SSLA can be recovered with 1.0mol/L H_2SO_4 solution, the recovery is approximately 99.6%. It has been proved from the cost analysis that the recovery of chromium(Ⅲ) from the chrome tanning wastewater by precipitation and adsorption processes is a promising and economically feasible technique.