Urea-modified Cu-based materials: Highly efficient and support-free adsorbents for removal of H2S in an anaerobic and dry environment

In this work, we report a novel urea-modified copper-based material (XUrea@Cu) obtained by directly calcinating a mixture of urea and copper nitrate. This material enables the efficient purification of H2S under dry and anaerobic conditions. The performance test results showed that the H2S capacity of the optimal adsorbent (2Urea@Cu) could reach 364.2 mg(H2S)∙gsorbent-1, which is much superior to those of other adsorbents in the literature. Further study demonstrates that the ultra-desulfurization performance of 2Urea@Cu is mainly attributed to the extensive alkaline site, the high concentrations of active oxygen, and the abundance of oxygen vacancy; which are quite effective for capturing H2S (acidic and strong reducibility). Interestingly, the deactivation adsorbent (De-2Urea@Cu) is mainly composed of high-purity CuS, which means that the Urea@Cu adsorbent can simultaneously achieve efficient purification of H2S and recovery of sulfur resources since CuS is a valuable product. In addition, in-situ FT-IR and theoretical calculation results indicate that H2S molecules dissociate on the CuO(1 1 1) surface by stepwise dehydrogenation, while S combines with adjacent Cu to form CuS. The consumption of active components (CuO) and the accumulation of reaction products (CuS) are the primary reasons for the deactivation of adsorbents. Considering the simple preparation process, low cost, and excellent H2S adsorption activity, these urea-modified copper-based materials are very promising H2S adsorbents.