Rational design of polar/nonpolar mediators toward efficient sulfur fixation and enhanced conductivity

Schematic of the classification of polar and nonpolar materials for LSBs.

Producing Effective and Clean Coke for Household Combustion Activities to Reduce Gaseous Pollutant Emissions

Nowadays, the gaseous pollutant emissions, including particulate matter (PM), sulfur dioxide (SO2), and nitrogen oxide (NOx) from household coal combustion, cause great threat to environment and public health by contributing to severe haze in China. Particularly, a clean coke free of the major pollutants precursors (sulfur and nitrogen compounds) by sulfur fixation and denitrification has been deemed as an effective strategy to reducing pollutants. In this paper, a preprocessed coke was prepared by co-pyrolysis of high-sulfur coal with the assistance of calcium-based and iron-based complexes at high temperature. The results show that high-temperature co-pyrolysis could remove the volatile compounds that are major precursors for the formation of gaseous pollutants from the raw coal. During the coking process, the sulfur can be removed by being fixed in the form of CaS in presence of a Ca-based complex, which could be beneficial for the CaSO4 during the coke combustion. The volatile nitrogen is transferred to the gas phase with the addition of Fe-based complexes, which effectively reduce the residual nitrogen in coke. As a result, Ca-based additives captured the released SO2 and formed CaSO4 during the combustion process. In addition, in the presence of Fe-based complexes, both char and CO react with NOx to form N2, which leads to a reduction in NOx emissions during combustion. Additionally, the replacement of current residential coal with a new type of clean coke is a facile method for reducing gaseous pollutant emissions from household activities to protect the atmospheric environment. The average emission factors (EFs) of PM, SO2, and NOx for the prepared clean coke were small during combustion and were much lower than the EFs of the tested raw coal, semicoke, and briquettes.

Cleaner Recycling of Spent Lead-Acid Battery Paste and Co-Treatment of Pyrite Cinder via a Reductive Sulfur-Fixing Method for Valuable Metal Recovery and Sulfur Conservation

This study proposes a cleaner lead-acid battery (LAB) paste and pyrite cinder (PyC) recycling method without excessive generation of SO2. PyCs were employed as sulfur-fixing reagents to conserve sulfur as condensed sulfides, which prevented SO2 emissions. In this work, the phase transformation mechanisms in a PbSO4-Na2CO3-Fe3O4-C reaction system were studied in detail. Furthermore, the co-treatment of spent LAB and PyCs was conducted to determine the optimal recycling conditions and to detect the influences of different processing parameters on lead recovery and sulfur fixation. In addition, a bench-scale experiment was carried out to confirm the feasibility and reliability of this novel process. The results reveal that the products were separated into three distinct layers: slag, ferrous matte, and crude lead. 98.3% of lead and 99% of silver in the feed materials were directly enriched in crude lead. Crude lead with purity of more than 98 wt.% (weight percent) was obtained by a one-step extraction. Lead contents in the produced matte and slag were below 2.7 wt.% and 0.6 wt.%, respectively. At the same time, 99.2% total sulfur was fixed and recovered.

Cleaner Extraction of Lead from Complex Lead-Containing Wastes by Reductive Sulfur-Fixing Smelting with Low SO2 Emission

A novel and cleaner process for lead and silver recycling from multiple lead-containing wastes, e.g., lead ash, lead sludge, lead slag, and ferric sludge, by reductive sulfur-fixing smelting was proposed. In this process, coke and iron-containing wastes were employed as reductive agent and sulfur-fixing agent, respectively. A Na2CO3-Na2SO4 mixture was added as flux. The feasibility of this process was detected from thermodynamic and experimental perspectives. The influence of Fe/SiO2 and CaO/SiO2, composition of the molten salt, coke addition, smelting temperature, and smelting time on direct Pb recovery and sulfur-fixation efficiency were investigated. The optimal process conditions were determined as follows: WCoke = 15% WPb wastes, W Na 2 CO 3 / W Na 2 SO 4 = 0.7/0.3, Fe/SiO2 = 1.10, CaO/SiO2 = 0.30, smelting temperature 1200 °C, and smelting time 2 h, where W represents weight. Under these optimum conditions, 92.4% Pb and 98.8% Ag were directly recovered in crude lead bullion in one step treatment, and total 98.6% sulfur was fixed. The generation and emissions of SO2 can be avoided. The main phases in ferrous matte obtained were FeS, NaFeS2, Fe2Zn3S5, and a little entrained Pb. The slag was a FeO-SiO2-CaO-Na2O quaternary melt.