PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
·
2019
·
IF 4.384
Wenying Guo,Sihai Zhang,Nengwu Zhu,Deliang Luo,Pingxiao Wu
In this study, a strategy was developed to directly recover high-purity Ag and other metals (especially Cu) from WECs to reduce the leaching of precious metals and promote the leaching of Cu and other metals. The results of SEM, EDS, XRD and ICP-OES clearly suggested that Ag and Cu were effectively released from WECs below 0.15 mm size, which contributed to the regulation of metals crystal types. The zero-valent copper from WECs was changed by roasting to form CuO and Cu 2 O, and the suitable samples of roasting at 400 °C for 3 h were confirmed experimentally. After the leaching processing under H 2 SO 4 (1 M) and H 2 O 2 (30%), the roasted particles were directly obtained, including Ag with 99.53 wt.% purity and more than 99.99% recovered, and Cu, Sn, Ni and Zn extracted by 99.67%, 90.71%, 73.05% and 99.32%, respectively. However, the unroasted particles would generate lower grade of Ag because other metals (e.g. Cu, Sn, Ni and Zn) were difficult to be leached from WECs. The leaching solution primarily included Cu ions (98.3%) and a little of the nickel (0.83%) and tin (0.86%) ions, which could recover copper by evaporation crystallization to form CuSO 4 (99.48 wt. %). The reaction mechanism of the process could be concluded that the copper state was transformed by mechanical separation and roasting to promote the leaching of various metals from Ag.
研究领域:
材料科学
·
环境工程
✓ 已验证
DOI
高影响因子
SCIENCE OF THE TOTAL ENVIRONMENT
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2019
·
IF 5.589
Qi-Su Huang,Wei Wu,Wei Wei,Bing-Jie Ni
Elemental Ag 0 is well known for its remarkable catalytic and antibacterial properties, thus the regeneration of valuable Ag 0 metal from Ag + wastewater is of great significance. In this study, a novel polyethylenimine (PEI) modified potassium tungsten oxide (N-K 2 W 4 O 13 ) adsorbent was prepared for Ag + removal and reduction to Ag 0 using glutaraldehyde as crosslinking agent. XPS and FT-IR spectra verified PEI successfully anchored on the surface O and W atoms of K 2 W 4 O 13 through aldehyde bridges. The content of PEI in N-K 2 W 4 O 13 was calculated as 8.74 wt% by TG curve. A heterogeneous PEI coating was observed in the SEM and TEM images. The N-K 2 W 4 O 13 exhibited larger Ag + uptake (48.25 mg/g) than the raw K 2 W 4 O 13 (42.50 mg/g) though required a longer equilibrium time. This was due to the combined results of strong chelation and weak electrostatic repulsion that meanwhile occurring on the positive-charged surface of N-K 2 W 4 O 13 . The maximum Ag + uptake on N-K 2 W 4 O 13 was 72.5 mg/g, which was larger than many of the reported adsorbents. Furthermore, the prepared N-K 2 W 4 O 13 displayed good anti-interference toward background ions (Na + , K + ) and hold a stable Ag + removal (>95%) after five runs of recycling tests. The mechanism studies elucidated that NH/ N groups from the PEI modified N-K 2 W 4 O 13 mainly accounted for the Ag + adsorption and Ag 0 recovery in the adsorption-reduction process. Ion-exchange between Ag + and K + from the N-K 2 W 4 O 13 lattice also occurred. This work provided a facile method to synthesize a promising adsorbent for Ag + wastewater remediation and valuable Ag 0 recovery.
研究领域:
环境科学
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材料科学
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
ENVIRONMENTAL POLLUTION
·
2019
·
IF 5.714
Jingjing Wang,Wenhui Zhang,Xinyu Kang,Changsen Zhang
High performance activated carbon (HPAC) supported nanoscale zerovalent iron (nZVI) was prepared and used for recovery of silver. This composite material was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The removal amount of Ag + increased with pH values and temperature. The removal process achieved equilibrium within 40 min and the maximum removal capacity was 986.5 mg/g at 298 K. The composite material showed fast adsorption rate and high adsorption capacity because the presence of high surface area activated carbon could effectively inhibit aggregation of nanoscale zerovalent iron, thus enhancing its reactivity. The Ag + removal followed pseudo-second-order kinetic model and Langmuir isotherm model. XPS and XRD characterizations were performed to elucidate removal mechanism. It could be concluded that both coordination adsorption and reductive precipitation contributed to removal of Ag + on the nZVI/HPAC.
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2020
·
IF 16.683
Meng Qiao,Xiaofei Wu,Shen Zhao,Ridha Djellabi,Xu Zhao
Due to the complicated chemical nature and toxicity of noble metal-cyanide complexes, the appropriate treatment of wastewaters contaminated with such pollutants is challenging. In this study, the simultaneous decomposition of Ag-cyanide and recovery of precious Ag from Ag-cyanide aqueous solution was investigated using a synergistic peroxymonosulfate (PMS)/g-C 3 N 4 nanosheets system under visible light (λ > 400 nm). The combination of g-C 3 N 4 (1.0 g/L) and PMS (0.5 mM) resulted in higher Ag-cyanide (0.45 mM) decomposition under visible light and Ag recovery efficiencies (74% and 68%, respectively) compared with single PMS oxidation or g-C 3 N 4 photocatalytic oxidation within 150 min. Ag species deposited on g-C 3 N 4 in the form of metallic Ag° and Ag 2 O may also further improve the decomposition of Ag-cyanide complexes. Ag species deposited on g-C 3 N 4 can enhance the separation of electron/hole charges of the photoactive g-C 3 N 4 . Quenching of reactive oxygen species (ROS) experiments and electron spin resonance (ESR) analysis showed the generation of SO 4 ·− , OH, O 2 − , 1 O 2 and e- species in this system, among them O 2 − , 1 O 2 , and e- were the most active species for the decomposition of Ag-cyanide complexes.
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Minerals
·
2019
·Vol. 9
·期 2
·119
·
IF 2.25
Yun Li,Shenghai Yang,Wenrong Lin,Pekka Taskinen,Jing He,Yuejun Wang,Junjie Shi,Yongming Chen,Chaobo Tang,Ari Jokilaakso
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-Na2SO4mixture was added as flux. The feasibility of this process was detected from thermodynamic and experimental perspectives. The influence of Fe/SiO2and 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,WNa2CO3/WNa2SO4= 0.7/0.3, Fe/SiO2= 1.10, CaO/SiO2= 0.30, smelting temperature 1200 °C, and smelting time 2 h, whereWrepresents 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 SO2can 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.Keywords:SO2-free sulfur fixing smelting;lead recycling;wastes co-treatment and recycling;lead-iron-containing wastes;molten salt;PbO-FeO-SiO2-CaO-Na2O phase diagram
研究领域:
冶金学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）