Bentao Yang

Formation of abiological granular sludge – A facile and bioinspired proposal for improving sludge settling performance during heavy metal wastewater treatment

Heavy metal contamination in wastewater poses a severe threat to the environment and public health. Chemical precipitation is the most conventional process for heavy metal wastewater treatment. However, the flocculent structure of chemical precipitation sludge raises the problem of poor sludge settling performance that is difficult to overcome. Inspired by the biological granular sludge (BGS) formation process, we report here a facile and effective strategy to produce abiological granular sludge (ABGS) to solve this problem. In this procedure, controlled double-jet precipitation was performed to simulate the cell multiplication process in BGS formation by controlling the solution supersaturation. Meanwhile, ZnO seeds and flocculant polyacrylamide were added to simulate the role of nuclei growth and extracellular polymeric substances in BGS formation process, respectively. This procedure generates ABGS with a dense structure, large size and regular spherical morphology. The settling velocity of ABGS can reach up to 3.0cms(-1), significantly higher than that of flocculent sludge (<1cms(-1)).

Pathway of zinc oxide formation by seed-assisted and controlled double-jet precipitation

Zinc oxide formation in seed-assisted and controlled double-jet precipitation (CDJP) was explored. Results show that the formation of ZnO involves the initial surface precipitation of β-Zn(OH)2 intermediates on seed surfaces, followed by fast surface phase transformation to ZnO. During this process, the seeds play the role of crystallization catalysts to promote ZnO formation in a short time at room temperature via changing the precipitation pathway. Meanwhile, CDJP ensures the effects of the seeds by controlling the solution supersaturation.

Transport and transformation of mercury during wet flue gas cleaning process of nonferrous metal smelting

Reducing mercury emission is hot topic for international society. The first step for controlling mercury in fuel gas is to investigate mercury distribution and during the flue gas treatment process. The mercury transport and transformation in wet flue gas cleaning process of nonferrous smelting industry was studied in the paper with critical important parameters, such as the solution temperature, Hg0 concentration, SO2 concentration, and Hg2+ concentration at the laboratory scale. The mass ratio of the mercury distribution in the solution, flue gas, sludge, and acid fog from the simulated flue gas containing Hg2+ and Hg0 was 49.12~65.54, 18.34~35.42, 11.89~14.47, and 1.74~3.54%, respectively. The primary mercury species in the flue gas and acid fog were gaseous Hg0 and dissolved Hg2+. The mercury species in the cleaning solution were dissolved Hg2+ and colloidal mercury, which accounted for 56.56 and 7.34% of the total mercury, respectively. Various mercury compounds, including Hg2Cl2, HgS, HgCl2, HgSO4, and HgO, existed in the sludge. These results for mercury distribution and speciation are highly useful in understanding mercury transport and transformation during the wet flue gas cleaning process. This research is conducive for controlling mercury emissions from nonferrous smelting flue gas and by-products.

The electrochemical selective reduction of NO using CoSe2@CNTs hybrid

Converting the NO from gaseous pollutant into NH4+ through electrocatalytical reduction using cost-effective materials holds great promise for pollutant purifying and resources recycling. In this work, we developed a highly selective and stable catalyst CoSe2 nanoparticle hybridized with carbon nanotubes (CoSe2@CNTs). The CoSe2@CNTs hybrid catalysts performed an extraordinary high selectivity for NH4+ formation in NO electroreduction with minimal N2O production and H2 evolution. The specific spatial structure of CoSe2 is conductive to the predominant formation of N-H bond between the N from adsorbed NO and H and inhibition of N-N formation from adjacent adsorbed NO. It was also the first time to convert the coordinated NO into NH4+ using non-noble metal catalysis. Moreover, the original concept of employing CoSe2 as eletrocatalyst for NO hydrogenation presented in this work can broaden horizons and provide new dimensions in the design of new highly efficient catalysts for NH4+ synthesis in aqueous solution.

Se reduction by CO/H2O in ionic liquid: acceleration effect by activating water molecules

To improve the safety and efficiency of the Se/CO/H2O redox process, five ionic liquids (1-butyl-3-methylimidazolium tetrafluoroborate, [bmin][BF4], 1-propyl-3-methylimidazolium tetrafluoroborate, [pmim][BF4], 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate, [bdmim][BF4], N-ethylimidazolium tetrafluoroborate, [eim][BF4], and 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate, [bmim][OTf]) were used as solvents instead of dimethyl formamide. The effect of the structure of anions and cations in ionic liquid, and water content on the Se reduction rate was investigated. In addition, the Se reduction pathway was also explored using UV-vis spectroscopy. The results show that the Se reduction rate is significantly increased by ∼1.4 times using [bmim][BF4], mainly by activating the water molecules.