Langlang Wang

Removing carbonyl sulfide with metal-modified activated carbon

A Cu-Co-K/activated carbon (AC) adsorbent has been developed for the removal of carbonyl sulfide (COS). The effects of COS concentration, reaction temperature and relative humidity were closely examined. A breakthrough of 33.23 mg COS·g−1 adsorbent at 60°C, under 30% relative humidity and in presence of 1.0% oxygen was exhibited in the Cu-Co-K/AC adsorbent prepared. Competitive adsorption studies for COS in the presence of CS2, and H2S were also conducted. TPD analysis was used to identify sulfur-containing products on the carbon surface, and the results indicated that H2S, COS and SO2 were all evident in the effluent gas generated from the exhausted Cu-Co-K/AC. Structure of the activated carbon samples has been characterized using nitrogen adsorption, and their surface chemical structures were also determined with X-ray photoelectron spectroscopy (XPS). It turns out that the modification with Cu(OH)2CO3-CoPcS-KOH can significantly improve the COS removal capacity, forming SO42− species simultaneously. Regeneration of the spent activated carbon sorbents by thermal desorption has also been explored.

Efficient removal of HCN through catalytic hydrolysis and oxidation on Cu/CoSPc/Ce metal-modified activated carbon under low oxygen conditions

The hydrogen cyanide (HCN) removal efficiency of activated carbon modified with different metal was studied under low oxygen conditions. When activated carbon was modified with Cu(NO)3, cobalt sulfonated phthalocyanine (CoSPc) and Ce(NO3)3·6H2O, its catalytic efficiency in HCN removal was significantly enhanced with the optimal conditions of 400 °C as the calcination temperature, 10% relative humidity and 1% oxygen concentration. And the catalytic hydrolysis and oxidation efficiency of AC–Cu–CoSPc–Ce was more than 98% at 200–350 °C with the maximum selectivity to N2 of 52.6% at 300 °C. Although both AC–Cu and AC–Cu–CoSPc–Ce catalysts were reliable and stable, AC–Cu–CoSPc–Ce had a better catalytic activity at lower temperature. According to BET and X-ray photoelectron spectroscopy (XPS) results, Cu was mainly in the form of CuO and Cu2O, Co was present in the form of Co2+ and Co0, and Ce was mainly in the form of CeO2 and Ce2O3 on the catalyst surface. The reaction pathways were proposed.

Coupling catalytic hydrolysis and oxidation on metal-modified activated carbon for HCN removal

A method of coupling catalytic hydrolysis and oxidation for HCN removal by metal-modified activated carbon (denoted as AC-M) was studied using a dynamic method in a fixed bed reactor. The results showed that impregnation of metal oxides on the activated carbon significantly enhanced the removal capacity for HCN. Among the different types of metal-modified catalysts, AC-Cu exhibited the highest catalytic activity. The AC-Cu catalyst showed >96% conversion of HCN at 200–350 °C. The selectivity of N2 in the conversion of HCN reached 48.8% at 300 °C. Oxygen concentration, relative humidity and calcination temperature can greatly influence the catalytic activity. In particular, the reaction temperature was determined to be a crucial factor. The detailed characterization of the catalyst was performed using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and temperature programmed desorption (TPD). The Cu 2p XPS spectra and XRD patterns indicated that CuO was formed as an active species for the catalytic removal of HCN. We concluded that AC-Cu could be used as a catalyst for the removal of HCN by coupling catalytic hydrolysis and oxidation.

Arsine adsorption in copper-exchanged zeolite under low temperature and micro-oxygen conditions

Arsenic pollution is a worldwide issue. Nearly all arsenic is converted to arsine (AsH3) under the reducing atmosphere required for the gasification process. Growing industrialization has increased AsH3 emissions, for example, the ore smelting process leads to AsH3 emissions. The conditions used in the ore smelting process are low temperature and micro-oxygen. A series of Hβ zeolites loaded on different metal oxides has been prepared using an impregnation method and tested for adsorption of arsine (AsH3) under low temperature and micro-oxygen conditions. Based on the results obtained from the adsorbent optimization experiments, Hβ zeolite modified with Cu(NO3)2 (denoted as Cu/Hβ) was found to possess a significantly enhanced adsorption removal ability towards arsine. The effects of the impregnation concentration, calcination temperature, reaction temperature, and oxygen content on the AsH3 removal process were investigated. The results indicate that adsorbents with 0.2 mol L−1 Cu(NO3)2 after calcination at 400 °C have superior activity for AsH3 removal. In addition, a breakthrough capacity of 43.7 mg AsH3/g adsorbent at 60 °C as well as 1.0% oxygen was observed with Cu/Hβ for the AsH3 adsorption process. The structure and surface properties of the Hβ zeolite samples were characterized by N2-BET (N2 adsorption/desorption), XRD (X-ray powder diffraction), XPS (X-ray photoelectron spectroscopy), and FTIR (Fourier transform infrared) spectroscopy. It is feasible that the exhausted Cu/Hβ can be regenerated by thermal desorption, and the adsorbents can be recycled at least two times with little capacity loss.

Removal of elemental mercury and divalent mercury with ammonium sulfide in smelting gas containing SO2

A set of simulation equipment is set up after the conditions of removing SO2 and heavy metal Hg (Hg 0 and Hg 2+ ) has been investigated, the results of the removal technology method of absorption Hg 0 , Hg 2+ in smelting gases containing SO2 with (NH4)2S is tested, and their composition of reaction products and sediment are analyzed with XRD and XPS. Obta ined that: when absorption concentration of (NH4)2S are 0.8 mol/L, in pH 7.0-3.0 removal efficiency of Hg 0 and SO2 is higher, temperature will affect the absorption of Hg 0 , when reaction temperature is 30˚C the absorption of Hg 0 can be achieved the best. Under these optimum conditions, the removal e fficiency of Hg 0, Hg 2+ and SO2 could reach 89.45%, 99.42% and over 99.99%, the participation of SO2 has a promote consequence on removal of Hg 0 . The main reaction product is HgS, HgSO4,