The proper disposal of Cu-smelting waste acid (CSWA) is a major challenge in sulfide ores pyrometallurgy industry due to its high content of H2SO4, extremely high concentration of As and multiple toxic metals. The neutralization precipitation using cheap CaO is the most widely used process in tackling CSWA. However, a large amount of hazardous wastes covering As and other heavy metals which requires further disposal is generated, and the valuable H2SO4 cannot be reused. Herein, anaerobic membrane bioreactor (AnMBR) is used to continuously produce gaseous H2S for sulfide precipitation of the refractory CSWA and simultaneous fabrication of photo-catalyst for the first time. The 200L AnMBR respectively gained the highest total H2S production of 6.41 g/ h and the highest gaseous H2S production of 5.05 g/h under the optimal conditions, being 3-9 times higher than previous reports by other types of bioreactors. And the sulfide precipitation triggered by the maximum gaseous H2S of 5.05 g/h harvested almost 100 % removal for Cu, As and Cd from CSWA within a short time from 0.35 to 3.69 days. Moreover, the phase 1 precipitate covering Cu-S compounds displayed an efficient photo-catalytic activity. The sulfide precipitation by AnMBR showed an application potential in tackling the refractory CSWA and fabrication of valuable nanoparticle photo-catalyst.

The pyrometallurgy coupling indirect bioleaching strategy is proposed for the recycling of WPCBs to avoid the disadvantages of time-consuming, low processing power, and relatively low efficiency of conventional bioleaching. The results show that under the pulp density of 2.5% (w/v), the low content (0.26 wt.%) of Ni in the raw WPCBs is completely extracted by indirect bioleaching, while the release rate of a high content (24.52 wt.%) of Cu is only 46.9%. However, the calcination pretreatment significantly improves Cu release by indirect bioleaching, and 100% Cu extraction is attained from the 600 degrees C-treated WPCBs at the high pulp density of 5.0% due to the formation of tractable CuO. Conversely, the release of Ni is inhibited by calcination evidently, and the indirect bioleaching efficiency of Ni declines from 34.9% to 10.1% when the pulp density lifts from 2.5% to 10.0% because of the formation of NiO with lower kinetics of acid-dissolution. On the other hand, due to the complete removal of Cu and the formation of insoluble NiO, the toxicity and environmental risk analysis indicates that the bioleaching residue of the 600 degrees C-treated WPCBs at the pulp density of 5.0% is completely detoxified and can be reused as non-hazardous materials safely, while the combination of the calcination and indirect bioleaching significantly reduces the environmental risk associated with the WPCBs. These findings provide the theoretical basis for a perfect combined process of pyrometallurgy and bioleaching for tackling the WPCBs from a technological perspective.

The ZMF@S10 composite that was synthesized by using spent Zn-Mn batteries and abandon SCR catalyst as the starting materials for magnetic photocatalysts with high photocatalytic activity is successfully prepared in this study. The results showed that the core TiO2 crystal structure will transform from anatase to rutile, which was then covered in the ZMF. The efficient photocatalytic performance of the composites under visible light is due to the inhibition of the recombination rate of photogenerated dots and holes on the surface of ZMF by the presence of rutile TiO2. Besides, all composites show good stability, regeneration performance, and easy recycling.

The vital functions of extracellular polymeric substances (EPS) have been well recognized in bioleaching of sulfide ores. However, no report is available about the role of EPS in bioleaching of spent catalyst. To completely and deeply understand the functions of EPS in bioleaching of spent catalyst, the generation behavior of EPS at various pulp densities during bioleaching was characterized by three-dimensional excitation-emission matrix (3DEEM), and its relevance with bioleaching performance and process parameters were analyzed using mathematical means. The results showed that the EPS contain humus-like substances as main component (>70%) and protein-like substances as minor component (<30%). Both total EPS and humus-like substances mainly keep growing over the whole duration of bioleaching at low pulp density of 5.0% or lower; whereas total EPS and humus-like fraction keep declining at high pulp density of 7.5% or higher. Among the total EPS and its components, humus-like substances only have a positive significant correlation with bioleaching efficiencies of both Co and Mo and affect bioleaching process more greatly due to greater correlation coefficient. Biofilm appears at the spent catalyst surface under 2.5% of pulp density mediated by EPS while no biofilm occurs at 10% of pulp density due to shortage of EPS, accounting for the great difference in bioleaching efficiencies between high and low pulp densities which are 48.3% for Mo and 50.0% for Co at 10% of pulp density as well as 75.9% for Mo and 78.8% for Co at 2.5% of pulp density, respectively.

综述了酸性矿山废水的产生、危害和当前对酸性矿山废水(AMD)的处理方法,重点介绍了应用硫酸盐还原菌(SRB)处理酸性矿山废水的研究进展(厌氧生物反应器技术、联合处理技术、微生物固定化技术以及微生物原位处理技术).利用硫酸盐还原菌处理酸性矿山废水是很有潜力的处理方法,具有成本低、可去除重金属离子且无二次污染的优点.在应用过程中,酸性矿山废水pH值较低的特点使得普通微生物无法生存,可通过驯化SRB使其具有更低的pH耐受值或者分离嗜酸性aSRB,或应用生物H2 S处理酸性矿山废水,使得在脱除重金属的同时能够实现污酸的回用.

The development of visible-light-responsive photocatalysts with high efficiency, stability, and eco-friendly nature is beneficial to the large-scale application of solar hydrogen production. In this work, the production of biosynthetic ternary ZnCdS photocatalysts (Eg = 2.35–2.72 eV) by sulfate-reducing bacteria (SRB) under mild conditions was carried out for the first time. The huge amount of biogenic S2− and inherent extracellular proteins (EPs) secreted by SRB are important components of rapid extracellular biosynthesis. The ternary ZnCdS QDs at different molar ratios of Zn2+and Cd2+ from 15:1 to 1:1 were monodisperse spheres with good crystallinity and average crystallite size of 6.12 nm, independent of the molar ratio of Cd2+ to Zn2+. All the ZnCdS QDs had remarkable photocatalytic activity and stability for hydrogen evolution under visible light, without noble metal cocatalysts. Especially, ZnCdS QDs at Zn/Cd = 3:1 showed the highest H2 production activity of 3.752 mmol·h−1·g−1. This excellent performance was due to the high absorption of visible light, the high specific surface area, and the lower recombination rate between photoexcited electrons and holes. The adhered inherent EPs on the ZnCdS QDs slowed down the photocorrosion and improved the stability in photocatalytic hydrogen evolution. This study provides a new direction for solar hydrogen production.

The biosynthesis of metal nanoparticles/QDs has been universally recognized as environmentally sound and energy-saving, generating less pollution and having good biocompatibility, which is most needed in biological and medical fields. In the arena of chemical routes, however, biosynthesis has long been criticized for its low productivity, time-consuming process, and poor control over size, shape and crystallinity, keeping the much-needed technology away from practical application. In this work, a rapid and extracellular biosynthesis of multi-colour ternary ZnxCd1-xS QDs by a mixed sulfate-reducing bacteria (SRB)-derived supernatant was carried out for the first time to solve the problems plaguing this field of biosynthesis. The results showed that about 3.5 g L-1 of ZnxCd1-xS QDs with size of 3.50-4.64 nm were achieved within 30 minutes. The PL emission wavelength of ZnxCd1-xS QDs increased from 450 to 590 nm to yield multicolor QDs by altering the molar ratio of Cd2+ to Zn2+. The SRB-biogenic ZnxCd1-xS QDs have high stability in gastric acid and at high temperature, as well as excellent biocompatibility and biosafety, successfully entering growing HeLa cells and labelling them without detectable harm to cells. The SRB-secreted peculiar extracellular proteins (EPs) play a decisive function in the time-saving, high-yield biosynthesis of PL-tuned multicolor QDs, which cover an abnormally high concentration of acidic amino acids to provide tremendous negatively charged sites for the absorption of Cd2+/Zn2+ for rapid nucleation and biosynthesis. The strongly electrostatic connection between the QDs and the EPs and the increasing amount of EPs attached to the QDs in response to the increase of Cd2+ concentration account for their high stability and excellent biocompatibility.

针对铅锌冶炼废渣组分复杂、含有多种金属类型、难以用单一沥浸体系溶释所有目标金属的特点,提出自养-异养分步生物沥浸的处理思想.结果表明:自养生物沥浸对锌、镉、铟、砷、铅的最高沥浸效率分别为90％、86％、71％、25％、12％,对银的沥浸效率为0;异养生物沥浸对于自养生物沥浸残渣可获得最高37％ 的银沥浸效率,而铅锌冶炼废渣最高只有6％ 的银沥浸效率.因此,采用自养-异养分步生物沥浸铅锌冶炼废渣中的有价/有毒金属是一种铅锌冶炼废渣资源化的新途径.

光催化纳米材料是指能直接将太阳能转化为化学能来进行催化的纳米材料.因能直接利用太阳能这一特性,光催化纳米材料成为了缓解能源短缺和环境污染最有潜力的一类材料.光催化纳米材料的制备方法多种多样,其中,微生物制备法是利用微生物生长代谢合成光催化纳米材料,因微生物生长周期短、反应条件简单、无二次污染、节能环保等优点,成为现今极具发展潜力的、绿色环保的制备方法.对此研究者们进行了大量的研究探索.结合了近十年来有关微生物法制备光催化纳米材料的研究文献,介绍了用微生物法合成的各种纳米光催化材料,包括金属单质、硫族金属化合物、金属氧化物、复合材料及其它.重点阐述了光催化纳米材料的微生物制备过程及机理,介绍了各种光催化纳米材料的应用及光催化机理,最后,对光催化技术和微生物制备未来的研究进行了展望.

Abstract Background: Bioleaching is an important technology for treating electroplating sludge. Previous researches have focus on improving the leaching rate of metals in electroplating sludge by bioleaching. However, the concentration of heavy metals in the leachate after single leaching was lower, which is quite unfavorable for subsequent metal recovery. Additionally, membrane bioreactors (MBRs) have been widely used in the field of sewage treatment. Research on the application of bioleaching technology combined with MBRs to enrich metals in electroplating sludge has not been reported. Therefore, in this study, we first combined bioleaching technology and MBRs for metal enrichment in electroplating sludge to obtain the key technology of "acid production - electroplating sludge leaching - leachate regeneration -repeated electroplating sludge leaching - achievement of valuable metal enrichment".Results: In this research, through scaling up from the laboratory scale (shake flasks) to a factory-scale application (10 m³ membrane bioreactors), we mastered the key technology of acid production by acidophilic microorganism, and the acid solution can be repeatedly used for metal leaching. The results showed that the MBR maintained high-density cell growth (≈2.1×109/mL) and a stable sulfuric acid production rate (850 L/h) throughout the entire operational period. Under the above conditions, the maximum cycle number (10 times) for enrichment of the target metals in the electroplating sludge was obtained. Additionally, after the end of the cycle enrichment process, the concentrations of the target metals Ni+, Cu2+, and Zn2+ were 13.867 g/L, 18.118 g/L and 21.075 g/L, respectively, which were highly enriched.Conclusions: This study first solved the difficulties in the industrialization of bioleaching electroplating sludge through combining bioleaching technology and MBRs. Furthermore, this research can provide a demonstration project for the industrial application of MBR-bioleaching technology in electroplating sludge, with a view to applying this technology to the disposal of more types of hazardous waste.

A considerable amount of brake pad waste which is composed of phenolic resin and a variety of toxic heavy metals is produced both in China and around the world owing to the flourishing automobile industry. The safe, low cost and eco-sound bioleaching was utilized to extract the valuable metals Cu and Zn from the waste. The results showed that although bioleaching is more efficient in the extraction of Cu and Zn than the chemical counterpart, rather low bioleaching yields of 34% for Cu and 72% for Zn were obtained because of the complicated components and refractory nature of the waste. However, a low-temperature thermal pretreatment at 400 °C notably lifted the bioleaching efficiencies of Cu and Zn to 98% and nearly 100%, respectively. The thermal treatment removed the oil substances, transformed the acid insoluble Cu0 into acid soluble CuO and destroyed the chelation/complexation of the phenolic resin to loose Cu and Zn, promoting bioleaching performance of Cu and Zn. The combined processes of low-temperature thermal pretreatment and bioleaching is totally qualified for the extraction of Cu and Zn from the refractory waste.

Synthesis of Zn-Mn ferrite from spent Zn-Mn batteries using a multi-step process of bioleaching and co-precipitation represents a promising means in waste management of the spent batteries. However, the low pulp density of 1.0% in bioleaching process means a low yield of Zn-Mn ferrite. In this work, the cheap and benign Fe3+ was used to replace dangerous H2SO4 or expensive Cu2+ to promote bioleaching performance of spent batteries at a high pulp density of 5.0% for synthesis of Zn-Mn ferrite for the first time. The results displayed the addition of Fe3+ greatly enhanced bioleaching of spent batteries. The extraction efficiency of Zn and Mn increased from 34.5% to 29.4% to the maximum of 85.1% and 83.2%, respectively, when the concentration of added Fe3+ increased from 0 to 5.0 g/L. The added Fe3+ motivated more generation of both Fe2+ and sulfur to promote the growth of both Leptospirillum ferriphilum and Acidithiobacillus thiooxidans, respectively, attaining a higher bioleaching rate. The electro - chemical analysis also revealed the highest J(Corr) of 0.571 mA cm(-2) occurred when the concentration of added Fe3+ was 5.0 g/L. The addition of Fe3+ at 5.0 witnessed the maximum synthesis yield of Zn-Mn ferrite (52.6 g/L). (C) 2019 Published by Elsevier Ltd.

Semiconductor Cu2-xSe nanospheres were successfully biosynthesized based on bioreduction of SeO32- into Se2- by the selenite-reducing bacterium, Pantoea agglomerans. The Cu2-xSe nanospheres had excellent crystallinity with a face-centered cubic structure and an average diameter of 80 nm. Composition and oxidation states analysis using X-ray photoelectron spectroscopy and X-ray energy dispersive spectroscopy followed by optical characterization using ultraviolet-visible and Fourier transform infrared spectroscopy confirmed that the biosynthesized Cu2-xSe nanospheres were capped by proteins. The extracellular proteins which mediated biosynthesis were visualized by excitation-emission matrix fluorescence spectroscopy. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis revealed that the molecular masses of proteins were about 110, 50, 38, 35 and 25 kDa. The biosynthesized Cu2-xSe nanospheres showed an excellent and stable photocatalytical activity under sunlight irradiation in the degradation of methylene blue for four cycles. This study put forward a green and toilless way to manufacture copper selenide nanoparticles using a biological process.

以含铜废水为铜源、硫化钠为硫源,在常温常压的条件下,通过硫酸盐还原菌产生的胞外多聚物调控形成硫化铜纳米粒子,并对合成的材料进行XRD、TEM、HRTEM、EDS、UV-Vis等形貌表征,结果显示该材料平均粒径为8.98 nm,粒径分布比较均匀,结晶性良好.以亚甲基蓝为例,进行染料的光催化降解,表现出良好的光催化性,胞外多聚物的加入更提高了光催化稳定性,为印染废水等有机污染物的降解提供新思路.该方法合成工艺简单、成本低廉、绿色环保、易于工业化生产,使含铜废水实现资源化利用,有较大的实用价值.

This work describes a high-yield extracellular biosynthesis of ZnS QDs via a unique molecular mediation mechanism driven by the mixed sulfate reducing bacteria (SRB). The mixed SRB have obtained the highest ever ZnS QD biosynthesis rate of 35.0-45.0 g/(L.month). The biogenic ZnS QDs with an average crystallite size (ACS) of 6.5 nm have greater PL activity and better uniformity than that of a chemical route. Peculiar extracellular proteins (EPs) with molecular weights of approximately 65 and 14 kDa specially adhere to the ZnS QDs, which cover extraordinarily high contents of acidic amino acids (14.0 mol % Glu and 13.0 mol % Asp) and of nonpolar amino acids (12.0 mol % Ala, 11.0 mol % Gly, and 7.0 mol % Phe), for novel molecular mediation. The vast amount of negative charges in Glu and Asp guides the strong absorption between the EPs and Zn2+ via electrostatic attraction to reach a maximum absorption capacity of 745.9 mg/g within 2.0 h, motivating large and rapid nucleation as the first step of biosynthesis. Meanwhile, bridging and interlinkage occur inside the EPs or between the EPs via hydrophobic interactions dominated by the nonpolar amino acids, resulting in the formation of massive microcavities to control and restrict the growth of ZnS QDs as a template. The novel molecular mediation mechanism triggered by the peculiar EPs with an extraordinary amino acid composition and structure accounts for the high-yield biosynthesis of ZnS QDs. The mixed SRB have also successfully fabricated other metal sulfide QDs, including PbS, CuS, and CdS, through the novel molecular mediation.

通过介绍三种典型固体废弃物,进一步阐述其危害.对微生物技术在城市生活垃圾、涉重危废和工业固体废弃物中的应用和研究进展进行了综述,分析了微生物处理存在的问题和局限性,最后展望了微生物处理技术在固体废弃物处理中的应用前景.

A bioleachate containing high-content Mn and low-content Fe is required for the production of electrolytic manganese metal (EMM). To produce the qualified bioleachate, bioleaching of Mn from a low-grade MnO2 ore by a mixed autotrophic culture in presence of combined energy matters of pyrite and sulfur and simultaneous removal of Fe using waste electrolytic manganese anolyte (WEMA) containing high concentration of NH4+ as both nitrogen source and iron scavenger were investigated. The optimal conditions for both the maximum Mn release from the MnO2 ore and the maximum Fe precipitation from the bioleachate were determined via Plackett-Burman design, Steepest Ascent design and Box-Behnken design, which were listed as follows: 6% (v/v) of WEMA addition, 140 rpm of shaking speed, 250 mesh of ore particle size, 1.0 g L-1 of KH2PO4, pH value adjustment at 2.4, ratio of pyrite to sulfur at 14:10 (g. L-1), incubation temperature at 31 degrees C, and bioleaching period of 14 days at a fixed pulp density of 100 g L-1. The predicted values were 79.6% for the Mn extraction efficiency and 0.69 g L-1 for the total Fe residual concentration respectively, being very close to the measured values of 78.5% and 0.73 g L-1 in the confirmation experiments. The addition of 6% WEMA instead of (NH4)(2)SO4 resulted in an increase of 41% in the cell density from 1.20 x 10(8) to 1.69 x 10(8) mL(-1) after 14 days of culture, displaying that the WEMA was competent to be an nitrogen source for the bioleaching. On the other hand, the addition of WEMA enhanced the formation of more ammoniojarosite to greatly reduce the Fe residual concentration from 2.19 to 0.73 g L-1, accompanying 7% of loss rate in Mn extraction due to possible Mn adsorption onto the ammoniojarosite. The present study demonstrated that the WEMA as a byproduct of EMM industry is qualified to be both the nitrogen source for efficient bioleaching of low grade MnO2 ore and the Fe scavenger for simultaneous removal of Fe from the bioleachate, which is advantageous for both reduction of bioleaching cost and the closed loop recycling of waste in preparation of EMM. (C) 2017 Elsevier Ltd. All rights reserved.

Metal sulphide quantum dots (QDs) have broad applications. Sulphate-reducing bacteria (SRB) have been recognized as synthesizers of metal sulphides, with the characteristics of a high-production efficiency and easy product harvest. However, SRB are incapable of synthesizing metal sulphide QDs. In the present study, cheap hydroxypropyl starch (HPS) was used to assist SRB in manufacturing the ZnS QDs. The results exhibited that the HPS accelerated the growth of SRB and reduction of SO4 2+ into S2−, while it blocked the precipitation between S2− and Zn2+ to control the nucleation and growth of ZnS, resulting in the formation of ZnS QDs. When the HPS concentration increased from 0.2 to 1.6 g/L, the average crystal size (ACS) of ZnS QDs dropped from 5.95 to 3.34 nm, demonstrating the controlled biosynthesis of ZnS QDs. The ZnS QDs were coated or adhered to by both HPS and proteins, which played an important role in the controlled biosynthesis of ZnS QDs. The remarkable blue shift of the narrow UV absorption peak was due to the quantum confinement effect. The sequential variation in the colour of the photoluminescence spectrum (PL) from red to yellow suggested a tunable PL of the ZnS QDs. The current work demonstrated that SRB can fabricate the formation of ZnS QDs with a controlled size and tunable PL at a high-production rate of approximately 8.7 g/(L × week) through the simple mediation of HPS, with the yield being 7.46 times the highest yield in previously reported studies. The current work is of great importance to the commercialization of the biosynthesis of ZnS QDs.