Feasibility of removal S−2 from Kraft black liquor recovery cycle with synthetic adsorbents (Cu-PAC and Cu-GAC)

Sulfide ions (S−2) derived from Na2S in black liquor, after the pulping process, is the source of production H2S during of black liquor recovery cycle in Kraft pulp and paper industries. Tow adsorbents (Cu-PAC, Cu-GAC) by loading Cu+2 on powder activated carbon (PAC) and granular activated carbon (GAC) were synthesized to created more adsorption sites and were improved their selectivity for removing S−2 from black liquor with 3 level of sulfidity (18, 20 and 22 %). The adsorbents were characterized by BET, FTIR, SEM, and EDX. Adsorption of S−2 for Cu-PAC and Cu-GAC were fitted well with Freundlich and Langmuir isotherm model respectively and both of the adsorbents followed pseudo-second-order kinetic. The results of thermodynamic parameters showed the endothermic process. The removal efficiency results showed Cu-PAC has better performance than Cu-GAC. This is due to the higher specific surface area of Cu-PAC, which has led to more adsorption sites for S−2. By considering appropriate temperature conditions and direct effect of the S−2 on the production of H2S during of black liquor recovery cycle, Cu-PAC will be able to prevent H2S production and odorous the black liquor recovery cycle by removing 79.89 % of the S−2.