Evaluation of a sulfidogenic system fed with microalgal biomass of Chlorella pyrenoidosa as an electron donor: Sulfate reduction kinetics

In this study, a sulfidogenic reactor fed with microalgal biomass of Chlorella pyrenoidosa as an electron donor was operated in a continuous mode. This study evaluated the influence of various initial sulfate concentration from 1.0 to 2.5 g/L on anaerobic sulfate reduction kinetics by a sulfidogenic enrichment culture predominantly Desulfovibrio sp. VSV2. It was observed that volumetric sulfate reduction rate (VSRR) was consistently increasing with an increase in volumetric sulfate loading rate (VSLR) across the retention time of 7–10 days. For a retention time of 7 days, the maximum VSRR was noted as 0.0050 g/(L.h) with a corresponding VSLR of 0.0089 g/(L.h). When retention time was maintained for 10 days, a maximum sulfate reduction of 65% and a maximum bacterial concentration of 1.632 g/L were achieved for an initial sulfate concentration of 1.5 g/L. It was concluded that VSLR facilitated through both dilution rate and initial sulfate concentration had a significant influence over sulfate reduction kinetics. The results of the study suggested that the microalgal-fed sulfidogenic system could be effectively employed for reduction of sulfate from sulfate-rich wastewater.     

Microscopic Methods for Identification of Sulfate-Reducing Bacteria from Various Habitats

This paper is devoted to microscopic methods for the identification of sulfate-reducing bacteria (SRB). In this context, it describes various habitats, morphology and techniques used for the detection and identification of this very heterogeneous group of anaerobic microorganisms. SRB are present in almost every habitat on Earth, including freshwater and marine water, soils, sediments or animals. In the oil, water and gas industries, they can cause considerable economic losses due to their hydrogen sulfide production; in periodontal lesions and the colon of humans, they can cause health complications. Although the role of these bacteria in inflammatory bowel diseases is not entirely known yet, their presence is increased in patients and produced hydrogen sulfide has a cytotoxic effect. For these reasons, methods for the detection of these microorganisms were described. Apart from selected molecular techniques, including metagenomics, fluorescence microscopy was one of the applied methods. Especially fluorescence in situ hybridization (FISH) in various modifications was described. This method enables visual identification of SRB, determining their abundance and spatial distribution in environmental biofilms and gut samples.     

镓锗铜萃余液综合利用研究与应用

本文针对镓锗铜综合回收系统产出的萃余液,设计通过中和氧化除杂、锌粉置换除铜镉、有机试剂除钴镍、纯碱法生产碱式碳酸锌、高温煅烧生产活性氧化锌和一步法生产元明粉的生产工艺流程,有效的将镓锗铜萃余液分类分离富集,产出具有价值的富集渣和工业产品,进一步提升综合回收经济效益。     

Remediation of oil spill polluted water from Niger Delta Nigeria by sorption onto ammonium sulfate modified Dialium guineense seed husk

The abstraction of crude oil molecules from aqueous solution (produced water) and from real petroleum polluted water (collected from River State, Nigeria) by Dialium guineense Seed Husk (DGSH) and its ammonium sulfate functionalized form (AS-DGSH) was studied using a batch technique. The sorbents were characterized using Fourier transform infrared (FTIR), BET surface area analysis and the Scanning electron microscopy (SEM). Crude oil characterization revealed a light crude oil based on the API gravity of 35.6⁰. The Langmuir and Freundlich models gave good fits for crude oil sorption on DGSH and AS-DGSH respectively. The sorbents were found to remove over 50% of crude oil from the real polluted water at the natural pH of 6.1 and showed increase in removal with increase in sorbent dose. The potential of DGSH and its ammonium sulfate modified derivative as effective low cost sorbents for oil spill treatment was established.     

Behavior of sulfate in preparation of single light rare earth carbonate by Mg(HCO_3)_2 precipitation method

The precipitation of the water-leaching solution of Baotou mixed rare earth(RE) concentrate roasted with sulfuric acid using ammonium bicarbonate for producing RE carbonate produces a mass of ammonia-nitrogen wastewater because of the relatively low solubility of rare earth sulfate.To solve the serious problem of ammonia-nitrogen pollution,new precipitators need to be developed urgently so as to meet the requirements of environmental protection and impurities content of the product(SO_4~(2-)1.8 wt% in RE carbonates products).In this paper,we studied the effects of feeding modes on the behavior of SO_4~(2-) during the preparation of light RE carbonate(RE=La,Ce,Pr,Nd) from their sulfate solutions using Mg(HCO_3)_2 as a precipitant.The results indicate that the contents of SO_4~(2+) in the La and Ce precipitates using positive feeding mode exceed 16 wt% because of the formation of La2(CO_3)_(2.15)(-SO_4)_(0.85)·4 H_2 O and Ce2(CO_3)_(2.15)(SO_4)_(0.85)·3 H_2 O,while those of the Pr and Nd precipitates are 4 wt%-5 wt%since they exist in the form of n-carbonate.The precipitates prepared using synchronous feeding mode are all RE carbonate with only 4 wt%-5 wt% of SO_4~(2-) enclosed in the precipitation.The content of SO_4~(2-) in the RE carbonate obtained using reverse feeding mode is the lowest.Among them,the content of SO_4~(2-) in La precipitate is only 1.40 wt%.Both synchronous and reverse feeding modes can effectively reduce the content of SO_4~(2-)in RE carbonate,which provides theoretical guidance for the preparation of qualified light RE carbonate products by Mg(HCO_3)_2 precipitation method.     

Hot corrosion of TBC-coated components upon combustion of low-sulfur fuels

Gas turbine reliability is a crucial requirement for passenger safety in aviation and a secure energy supply. Hence, corrosive degradation of combustor parts, vanes, and blades in gas turbines must be prevented. One of the most severe forms of corrosion is alkali-sulfate-induced hot corrosion, which is associated with internal sulfidation of components and is usually anticipated to fade in importance in the absence of sulfur. However, the literature suggests that hot corrosion might still occur in low-sulfur combustion gases. In this study, established thermodynamic modeling methods are used to analyze the low-sulfur hot corrosion regime. Liquid sodium chromate is found to be stable in these conditions. A comparison of calculation results and engine findings suggests that high alkali levels can negatively impact thermal barrier coating life even if sulfur is absent in the fuel. Laboratory tests are carried out to validate the chromate formation on MCrAlY-coated specimens. It is shown that molten sodium chromate can alter the oxidation behavior of MCrAlY, promoting the formation of voluminous spinel. This represents a new and different form of hot corrosion compared to type I hot corrosion.     

X射线荧光光谱法测定氧化铝中杂质含量的质量控制方法

为满足本公司生产需求,实验室采用X射线荧光光谱法(XRF)测定氧化铝中SiO₂、Fe₂O₃、Na₂O含量,而XRF检测结果的准确性取决于日常质量控制效果。工作中总结出一套以XRF设备分析原理为基础结合氧化铝中SiO₂、Fe₂O₃、Na₂O测定经验的有效质量控制方法,论述了质量控制计划制定的依据及质量控制方法选择的原则,从仪器设备检测状态控制、样品制备方法选择、XRF漂移校正、标准样品检测、方法比对、人员比对及留样再测等方面详细介绍了内部质量控制方法,同时运用实验室间比对及测量审核两种外部质量控制方法对内部质量控制效果进行检验。通过统计分析内外部质量控制数据,发现实验室用XRF测定粉末压片法制样的氧化铝中SiO₂、Fe₂O₃、Na₂O含量,检测结果准确可靠,证明质量控制方法有效。该套质量控制经验对于XRF测定其他材料中杂质元素含量的质量控制方法的建立同样具有参考借鉴意义。     

温度对氢气还原铁氧化物过程膨胀性能的影响

摘要：为探究球团矿还原过程中产生恶性膨胀的问题，研究了温度对H2还原Fe2O3样条过程中膨胀性能的影响，并采用PCY G膨胀仪进行在线检测，通过对比不同温度条件下还原产物的外观形貌与显微结构，解释还原反应产生膨胀差异的原因。实验结果表明，H2还原气氛下，随着还原温度的升高，800℃下样条膨胀最大，样条的最大膨胀量出现先增加后减小的趋势；还原反应达到最大膨胀量所用时间逐渐缩短。随着还原温度的升高，铁相连接更加紧密，样条内外产生更大应力差，致使900℃条件下的还原反应提前进入铁相收缩的状态。     

锰氧化物活化过硫酸盐降解有机污染物的研究进展

基于硫酸根自由基(SO_4~-·)的高级氧化技术是近年来迅速发展起来的一种水污染控制技术。非均相活化或硫酸盐诱导产生(SO_4~-·)具有高效、无二次污染等优势,其中锰氧化物是一类廉价、高效的过硫酸盐活化材料。综述了四类锰氧化物在活化过硫酸盐降解有机污染物的研究进展。