Chlorine and heavy metals removal from municipal solid waste incineration fly ash by electric field enhanced oxalic acid washing.

Electric field enhanced oxalic acid (H2C2O4) washing was conducted to examine the simultaneously removal efficiency of heavy metals (HMs) and chlorine, especially insoluble chlorine from municipal solid waste incineration fly ash (MSW FA). Results show that chlorine and HMs can be effectively removed with a total chlorine, As, Ni and Zn removal rate of 99.10%, 79.08%, 75.42% and 71.43%, when the electrode exchange frequencies is 40 Hz, current density is 50 mA/cm2, H2C2O4 adding amount is 0.5 mol/L and the reaction time is 4 h. Insoluble chlorine removal efficiency is up to 95.32%, much higher than reported studies. And the chlorine content in the residue is lower than 0.14%. Meanwhile, HMs removal efficiency is remarkable, 41.62%-67.51% higher than that of water washing. The high-efficient removal effect is caused by the constantly changing direction of electrons hitting the fly ash surface, which provides more escape channels for internal chlorine and HMs. These results proved that electric field enhanced oxalic acid washing could be a promising method for removing contaminants from MSWI fly ash.

Preparation of Silica Aerogels by Ambient Pressure Drying without Causing Equipment Corrosion.

The silica aerogels were prepared via a sol-gel technique and ambient pressure drying by using industrial solid wastes, dislodged sludges, as raw materials. A strategy was put forward to reduce the corrosion of equipment during the drying procedure. The pore structure, hydrophobicity, and thermal insulation property of the obtained samples were investigated in detail. The results show that the corrosion can be effectively avoided by using an equimolar mixture of trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS) as silylation agents. At a Si:TMCS:HMDS molar ratio of 1:0.375:0.375, the silica aerogels possess a desirable pore structure with a pore volume of 3.3 ± 0.1 cm³/g and a most probable pore size of 18.5 nm, a high hydrophobicity with a water contact angle of 144.2 ± 1.1°, and a low thermal conductivity of 0.031 ± 0.001 W/(m∙K).

Strategy and Technical Progress of Recycling of Spent Vanadium-Titanium-Based Selective Catalytic Reduction Catalysts.

Selective catalytic reduction denitration technology, abbreviated as SCR, is essential for the removal of nitrogen oxide from the flue gas of coal-fired power stations and has been widely used. Due to the strong demand for energy and the requirements for environmental protection, a large amount of SCR catalyst waste is produced. The spent SCR catalyst contains high-grade valuable metals, and proper disposal or treatment of the SCR catalyst can protect the environment and realize resource recycling. This review focuses on the two main routes of regeneration and recycling of spent vanadium-titanium SCR catalysts that are currently most widely commercially used and summarizes in detail the technologies of recycling, high-efficiency recycling, and recycling of valuable components of spent vanadium-titanium SCR catalysts. This review also discusses in depth the future development direction of recycling spent vanadium-titanium SCR catalysts. It provides a reference for promoting recycling, which is crucial for resource recovery and green and low-carbon development.

Cement kiln co-processing promotes the redevelopment of industrially contaminated land in China: Spatio-temporal features and efficiency analysis.

The cleanup and redevelopment of industrially contaminated land are essential for sustainable urban development, both from economic and environmental perspectives. Remediation efforts in developed countries have incurred high decontamination costs and administrative, monitoring, and enforcement requirements that are beyond the capabilities of many developing nations. Here, we reviewed the development of cement kiln co-processing of contaminated soils, a commonly used remediation strategy in China, and discussed the spatio-temporal features, benefits and efficiency of co-processing. Our results show that urbanization, the real estate market, and policies have impacts on the development of technology. By June 2021, cement kiln co-processing has disposed of approximately 2,633, 823 m3 of contaminated soils, and the average feed rates of organic pollutants, combined pollution, and heavy metals are 6%, 4%, and 3%, respectively. The average cost of co-processing contaminated soil is US$167.2 per cubic meter, which is lower than that of other conventional remedies. Based on the pollution status and cement production capacity, it is most likely that the co-processing strategy will be adopted by three countries of India, Indonesia, and Vietnam in the next few years. In the future, more data will be needed to quantify and assess the technology diffusion at the provincial level and the technological details of adopting this strategy.

The study on the effect of flotation purification on the performance of α-hemihydrate gypsum prepared from phosphogypsum.

Phosphogypsum (PG) is a massive industrial solid waste. In this paper, PG was purified by flotation method, and α-hemihydrate gypsum (α-HH) was prepared by the autoclaving method. The morphology of α-HH was adjusted by adding different doses of Maleic acid and Aluminium sulfate. The results showed that after flotation purification, the impurity content in PG was significantly reduced, the soluble phosphorus content decreased from 0.48 to 0.07%, the PG purity increased from 73.12 to 94.37%, and the PG whiteness risen from 19.4 to 40.5. Then the performance of α-HH prepared from PG before and after purification was compared. Fixing the amount of aluminium sulfate at 0.2 wt%, the reaction temperature at 140 °C, and the reaction time at 120 min, the average length/diameter ratio of α-HH crystals decreased from 7.2 to 0.6 as the amount of Maleic acid increased from 0 to 0.17 wt%. When the amount of Maleic acid was 0.13 wt%, the α-hemihydrate gypsum reached the best mechanical properties. The mechanical strength of high strength gypsum prepared from PG concentrate was significantly better than that of raw PG, indicating that flotation purification can effectively improve the performance of PG. In this study, a new method of PG purification and resource utilization was proposed.

Mesoporous Silica Membranes Silylated by Fluorinated and Non-Fluorinated Alkylsilanes for the Separation of Methyl Tert-Butyl Ether from Water.

It is of great significance to separate hazardous methyl tert-butyl ether (MTBE) from water in terms of environmental protection and human health. In the present work, α-Al2O3-suppotred silica membranes were prepared by the sol-gel and dip-coating technique. Two fluorinated alkylsilanes (1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) and trifluoropropyltriethoxysilane (TFPTES)) and two non-fluorinated alkylsilanes (octyltriethoxysilane (OTES) and propyltriethoxysilane (PTES)) were adopted to silylate the silica membrane by the post-grafting method which is used for the separation of MTBE from water by pervaporation. The results show that silylation enhances the hydrophobicity of silica membranes. The silylated silica membranes are selective towards MTBE, and the MTBE/water separation factor varies with grafting agents in the order: PFOTES > TFPTES > OTES > PTES. Membranes silylated with fluorinated carbon chains seem to be more selective towards MTBE than those with non-fluorinated carbon chains. The total flux is proportional to the pore volume of silica membranes, which depends on grafting agents in the order: PTES > PFOTES > OTES > TFPTES. Considering both total flux and selectivity, the PFOTES-SiO2 membrane is most effective in separation, with a MTBE/water separation factor of 24.6 and a total flux of 0.35 kg m-2 h-1 under a MTBE concentration of 3.0% and a feed temperature of 30 °C.

Heavy Metals Removing from Municipal Solid Waste Incineration Fly Ashes by Electric Field-Enhanced Washing.

Municipal solid waste incineration (MSWI) fly ash contains chlorides, heavy metals, and organic pollutants, which requires appropriate disposal to eliminate this risk. In this study, the effects of agents on heavy metals removal from MSWI fly ash by electric field-enhanced washing were systematically studied. The results show that when these fly ashes were washed at a current density of 35 mA/cm2, polarity switching frequency of 40 Hz, Ethylenediaminetetraacetic acid (EDTA) dosage of 0.5 mol/L, and a pH of 2 for 4 h, almost all of the Cd and Ni could be were removed, with a removal efficiency of 100.00% and 99.59%, respectively. Meanwhile, it also shows a significant effect on Cu and Zn, with a removal efficiency higher than 85%. After washing, the results of the sequential extraction procedure showed that the residual forms of Pb, Cu, Zn, Cd, Ni, and As increased obviously. According to GB5085.3-2007, the toxicity of the treated MSWI fly ash were below their thresholds of 5 and 1 mg/L for Pb and Cd, respectively. Thus, a novel technology for heavy metals removal from MSWI fly ash is proposed.

[Soluble expression and activity evaluation of SDF-1/54R, a specific antagonist of CXCR7].

OBJECTIVE: To construct a soluble prokaryotic expression vector of the CXCR7-specific antagonist SDF-1/54R and evaluate its activity. METHODS: SDF-1/54r gene amplified by PCR was inserted into the soluble expression vector pET-41a+ engineered with GST fusion tag, and the recombinant vector was transformed into E. coli strain BL21 (DE3). After IPTG induction of E. coli, the expressed recombinant protein was purified with GST affinity chromatography purification system and confirmed by SDS-PAGE and Western blotting assay. The target protein SDF-1/54R was obtained after digestion of the purified product with enterokinase. Breast cancer MCF-7 cells with high expression of CXCR7 was treated with SDF-1/54R and the cell proliferation and metastasis was evaluated with MTT and chemotaxis assays. RESULTS: The target protein SDF-1/54R obtained showed an obvious inhibitory effect on the proliferation and metastasis of MCF-7 cells as confirmed by MTT and chemotaxis assays. CONCLUSION: SDF-1/54R is a good antagonist of CXCR7 and shows a potential value as an effective anti-cancer agent.

[Construction of SDF-1P2G54, a specific antagonist of CXCR4].

OBJECTIVE: To obtain a specific antagonist of CXCR4, SDF-1P2G54 by mutating SDF-1 second proline (P) into glycin (G) and removing the α-helix of its C-terminal. METHODS: SDF-1p2g54 gene amplified by PCR was inserted into the vector pET-30a (+) and transformed into Escherichia coli (E. coli) strain BL21. After IPTG induction of E. coli, the expressed recombinant protein was purified with nickel-affinity chromatography column under denaturing conditions and refolded with gradient dilution and ultra-filtration. The chemotactic effect of SDF-1P2G54 on Jurkat cells and its antagonistic effect against SDF-1 were determined by transwell assay; flow cytometry was used to assay the ability of SDF-1P2G54 to induce calcium influx and CXCR4 internalization in MOLT4 cells. RESULTS: The recombinant protein SDF-1P2G54 completely lost the functions to activate CXCR4 or to induce transmembrane migration of Jurkat cells and calcium influx in MOLT4 cells, but maintained a high affinity to CXCR4. SDF-1P2G54 effectively inhibited the chemotactic effect of wild-type SDF-1 to Jurkat cells, and induced rapid CXCR4 internalization in MOLT4 cells. CONCLUSION: SDF-1P2G54 is a new antagonist of CXCR4 with a potential value as an effective inhibitor of HIV-1 infection, cancer metastasis or other major diseases.