Application of Response Surface Methodology for Preparation of ZnAC2/CAC Adsorbents for Hydrogen Sulfide (H2S) Capture

Abstract

Hydrogen sulfide (H2S) should be removed in the early stage of biogas purification as it may affect biogas production and cause environmental and catalyst toxicity. The adsorption of H2S gas by using activated carbon as a catalyst has been explored as a possible technology to remove H2S in the biogas industry. In this study, we investigated the optimal catalytic preparation conditions of the H2S adsorbent by using the RSM methodology and the Box–Behnken experimental design. The H2S catalyst was synthesized by impregnating commercial activated carbon (CAC) with zinc acetate (ZnAc2) with the factors and level for the Box–Behnken Design (BBD): molarity of 0.2–1.0 M ZnAc2 solution, soaked temperature of 30–100 °C, and soaked time of 30–180 min. Two responses including the H2S adsorption capacity and the BET surface area were assessed using two-factor interaction (2FI) models. The interactions were examined by using the analysis of variance (ANOVA). Hence, the optimum point of molarity was 0.22 M ZnAc2 solution, the soaked period was 48.82 min, and the soaked temperature was 95.08 °C obtained from the optimum point with the highest H2S adsorption capacity (2.37 mg H2S/g) and the optimum BET surface area (620.55 m2/g). Additionally, the comparison of the optimized and the non-optimized catalytic adsorbents showed an enhancement in the H2S adsorption capacity of up to 33%.