改性壳聚糖处理微生物浸矿废水

为解决采矿行业微生物浸矿酸性废水中和处理沉渣多、固液分离困难的问题,采用柠檬酸钠和环氧氯丙烷改性处理的壳聚糖在pH=2.2条件下吸附模拟废水中的Cu²⁺和Fe³⁺,用正交实验优化了壳聚糖改性工艺条件。实验结果表明,最适宜的工艺条件为：处理100 mL壳聚糖质量分数为2%的壳聚糖-冰醋酸溶液,柠檬酸钠缓冲溶液加入量200 mL,环氧氯丙烷加入量300 mL,反应时间6 h。改性壳聚糖对Fe³⁺的最大吸附容量为6.703 7 mg/g,对Cu²⁺的最大吸附容量为4.378 7 mg/g,Fe³⁺和Cu²⁺在改性壳聚糖上的吸附是单分子层形式。     

Assessment of long-term leaching from waste incineration air-pollution-control residues

Assessment of long-term leaching from MSWI air-pollution-control (APC) residues is discussed with respect to use in environmental impact assessment, such as life-cycle assessment (LCA). A method was proposed for estimating leaching as a function of the liquid-to-solid (L/S) ratio in a long-term perspective (L/S 5000l/kg). Data for changes in residue pH as a function of L/S was used in combination with pH dependent leaching data to predict leachate concentrations of Al, Ca, Cd, Ba, Mg, Ni, Pb, S, Pb, V and Zn as a function of L/S. Mass balance calculations were used to determine the element fractions leached with respect to L/S. The estimated long-term leaching from a semi-dry residue and a fly ash was compared with short-term leaching determined by batch tests at L/S 10l/kg, both carbonated and non-carbonated versions of the residues were investigated. Generally, very high L/S ratios above 2000l/kg were required to leach 20-30% of the solid contents. However, Ca and S were depleted at L/S 200-900l/kg. The long-term leachate concentrations were found to either remain at the same level as the initial leaching determined by the L/S 10 batch test, or to significantly decrease compared with the initial leaching. Only Al and Zn were found to show higher leachate concentrations at L/S ratios above 3000-5000l/kg. Carbonation generally prolonged the time needed for depletion from the solid residues; however, Ca and S were depleted faster than in the case of non-carbonated residues. This study shows that uncritical use of batch leaching data for assessing the potential leaching is highly problematic, and evaluations of residue disposal should include scenario specific quantification of the long-term leaching.     

Dissolution behavior of nutrient elements from dephosphorization slag in the weakly acidic solution

Journal of Material Cycles and Waste Management - Dephosphorization slag is primarily composed of CaO–SiO2–FeO–P2O5 slag system. As it contains abundant valuable components,...     

Chemical recycling of polycarbonate in dilute aqueous ammonia solution under hydrothermal conditions

Polycarbonate (PC) pellets were subjected to dilute aqueous ammonia solution under hydrothermal conditions in a semi-batch reactor at temperatures ranging from 433 to 463 K and at a pressure of 10 MPa. The PC pellets were almost completely converted to bisphenol A (BPA). During an initial certain period, referred to as an induction time, neither BPA nor total organic carbon in solution were detected, and the BPA yield increased with time. The monomer yield was well represented by a surface reaction model, two-thirds-order reaction with respect to the mass of unreacted PC. The overall rate constant of the reaction in 0.6 mol/kg aqueous ammonia solution at 433 K was about 15 times greater than that in 0.6 mol/kg NaOH solution. The rate constant at 433 K was proportional to the ammonia or NaOH concentration. There was a correlation between the induction time and temperature, as well as the ammonia or NaOH concentration. By carrying out the reaction in aqueous mixtures of (NH₄)₂SO₄ and NaOH at various concentrations of NaOH, ammonia was confirmed not to function as an alkaline reagent, but as a nucleophile reagent.     

钯负载泡沫镍电极电化学还原水中三氯乙酸

采用非电沉积法制备了钯负载泡沫镍电极,运用SEM技术对其进行了表征,并以其阴极、铂丝为阳极进行了电化学还原三氯乙酸的研究,考察了工艺条件对三氯乙酸降解效果的影响,并对反应动力学和反应机理和进行了探讨。结果表明:钯负载泡沫镍电极具有较高的比表面积和良好的储氢性能;以20 mmol/L硫酸钠为电解质,在电解温度为20℃、钯负载量为4.5 mg/cm~2的条件下恒流(10 mA)电解240 min,三氯乙酸降解率达99.76%,氯原子脱除率达73.86%;三氯乙酸的电化学还原反应过程以及三氯乙酸上未脱除氯原子浓度的变化均符合拟一级反应动力学方程;三氯乙酸在电化学还原过程中逐个脱除氯原子。     

金属有机骨架材料对水中有机酸的吸附性能

制备了MIL-100(Fe)、MIL-100(Cr)和NH_2-MIL-101(Al)3种金属有机骨架(MOFs)材料,考察了这3种MOFs材料对苯甲酸、水杨酸和山梨酸3种有机酸模拟废水的吸附处理效果,并与大孔吸附树脂D101进行了比较。实验结果表明:NH_2-MIL-101(Al)对苯甲酸的平衡吸附量最大,D101平衡吸附量中等,MIL-100(Cr)和MIL-100(Fe)平衡吸附量很小;NH_2-MIL-101(Al)对山梨酸具有优异的吸附性能,MIL-100(Cr)、MIL-100(Fe)和D101对山梨酸的平衡吸附量较低;3种MOFs材料和D101对水杨酸的平衡吸附量均很小。NH_2-MIL-101(Al)对山梨酸和苯甲酸的等温吸附过程可用Langmuir方程更好地拟合;NH_2-MIL-101(Al)对水杨酸的等温吸附过程可用Freundlich方程更好地拟合。     

Beyond the material grave: Life Cycle Impact Assessment of leaching from secondary materials in road and earth constructions

In industrialized countries, large amounts of mineral wastes are produced. They are re-used in various ways, particularly in road and earth constructions, substituting primary resources such as gravel. However, they may also contain pollutants, such as heavy metals, which may be leached to the groundwater. The toxic impacts of these emissions are so far often neglected within Life Cycle Assessments (LCA) of products or waste treatment services and thus, potentially large environmental impacts are currently missed. This study aims at closing this gap by assessing the ecotoxic impacts of heavy metal leaching from industrial mineral wastes in road and earth constructions. The flows of metals such as Sb, As, Pb, Cd, Cr, Cu, Mo, Ni, V and Zn originating from three typical constructions to the environment are quantified, their fate in the environment is assessed and potential ecotoxic effects evaluated. For our reference country, Germany, the industrial wastes that are applied as Granular Secondary Construction Material (GSCM) carry more than 45,000 t of diverse heavy metals per year. Depending on the material quality and construction type applied, up to 150 t of heavy metals may leach to the environment within the first 100 years after construction. Heavy metal retardation in subsoil can potentially reduce the fate to groundwater by up to 100%. One major challenge of integrating leaching from constructions into macro-scale LCA frameworks is the high variability in micro-scale technical and geographical factors, such as material qualities, construction types and soil types. In our work, we consider a broad range of parameter values in the modeling of leaching and fate. This allows distinguishing between the impacts of various road constructions, as well as sites with different soil properties. The findings of this study promote the quantitative consideration of environmental impacts of long-term leaching in Life Cycle Assessment, complementing site-specific risk assessment, for the design of waste management strategies, particularly in the construction sector.     

Desiccation of contaminant barrier materials amended with aqueous carboxymethyl cellulose solution

The stabilization potential of negatively charged sodium carboxymethyl cellulose (CMC) solution was assessed through investigation of its retention on clays under environmental conditions that promote soil desiccation. Sodium montmorillonite and kaolinite, commonly used in clayey soils, were mixed with aqueous CMC solutions in concentrations ranging from 0 to 10 g/L. These samples were dried in a specially-designed desiccation chamber which was operated at a temperature of 25°C and relative humidity of 30%. The results show an inverse proportionality between liquid loss and CMC concentration. Liquid loss from clayey soil follows the first-order reaction with a rate constant in the range of 4.6–6.7 mg/h. CMC half-lives on sodium montmorillonite during desiccation ranged from 103 to 181 h for an aqueous concentration range of 0.5–10 g/L compared to 108 h for distilled water. For kaolinite, more liquid was retained at 10 g/L CMC concentration than at other concentrations, but liquid retention was generally insignificant. These conclusions are valid for a desiccation duration of 890 h, a time that is reasonably simulative of the duration of exposures of bare ground surfaces to weather elements. The experimental results are explained in terms of the role of CMC molecular interactions with clay minerals in controlling fluid flow to desiccating clay surfaces.     

萃取法分离回收不锈钢酸洗污泥硫酸浸出液中的重金属

采用非皂化P204和皂化P204萃取剂对不锈钢酸洗污泥的硫酸浸出液进行萃取。在浸出液pH为0.80、非皂化P204体积分数为25%、萃取剂与浸出液体积比为1∶2、萃取时间为5 min的条件下,Fe~(3+)萃取率达99.64%,Cr~(3+)和Ni~(2+)萃取率为3.98%和6.99%,一次萃余液pH为0.64。采用皂化P204对除Fe~(3+)后的一次萃余液进行萃取,在P204体积分数为25%、萃取剂与浸出液体积比为1∶2、萃取剂皂化率为60%、一次萃余液pH为1.50、萃取时间为5 min的条件下,Ni~(2+)萃取率为93.12%,Cr~(3+)萃取率为20.69%,二次萃余液pH为2.63。     

Leaching behaviour of elements and evaluation of pre-treatment methods for municipal solid waste incinerator residues in column leaching tests.

Two new pre-treatment methods (water-washing/carbonation and carbonation/phosphate stabilization) of municipal solid waste (MSW) incinerator residues were evaluated by column leaching tests under aerobic conditions and anaerobic conditions (which were changed to aerobic conditions after 10 months). A mixture of bottom ash and fly ash (5:1 ratio) was pre-treated using each method. Shredded incombustible residues (SIR) were added to each ash preparation in proportions similar to the ratios present in landfills. For comparison, landfill wastes typical of Japan, namely, a mixture of bottom ash, chelating-pre-treated fly ash, and SIR, were also examined. Leachate samples were collected periodically and analysed over a 15-month period. When compared with chelating pretreatment, both water-washing/carbonation and carbonation/ phosphate stabilization reduced the leaching of Pb, Al, and Cu by about one to two orders of magnitude. Moreover, the initial concentrations of Ca and Pb in leachates from column of water-washing/carbonation were 56-57% and 84-96% less than those from the column of carbonation/phosphate stabilization. Therefore, water-washing/carbonation was considered to be a promising approach to obtain early waste stabilization and to reduce the release of heavy metals to near-negligible levels. The leaching behaviour of elements was also discussed.     

黄钠铁矾法氧化去除废锂电池硫酸浸出液中的铁

废锂电池中含有的Co、Ni和Cu等金属具有回收价值,Fe的存在降低了有价金属的回收效率。为去除废锂电池硫酸浸出液中的Fe,采用黄钠铁矾法分别以氯酸钠和过氧化氢作为氧化剂氧化除Fe,并优化了过氧化氢作为氧化剂的除Fe工艺参数。实验结果表明:过氧化氢作为氧化剂的除Fe效果好于氯酸钠;在n(H2O2)∶n(Fe)=0.5、初始溶液pH为1.8、终点pH为2.5、反应时间为2.0 h、搅拌速率为500 r/min的最佳工艺条件下,初始ρ(Fe)为0.212g/L的硫酸浸出液经除Fe处理后ρ(Fe)小于0.004 g/L,Fe去除率达98.0%,Co、Ni和Cu的损失率分别为1.04%、2.17%和1.41%。     

铜基多相催化剂催化氧气氧化降解水中水合肼

制备了3种铜基多相催化剂,用于催化氧气氧化降解水中水合肼。实验结果表明:三组分催化剂c-CuZnCr比单组分催化剂CuO(c-Cu)和双组分催化剂c-CuZn具有更好的催化性能;在200 mL浓度0.04 mol/L的水合肼水溶液中投加23 mg c-CuZnCr,常温常压下反应360 min,水合肼的降解率达99.96%;c-CuZnCr在使用中稳定性好,循环使用5次未见活性降低。表征结果显示,三组分催化剂具有最大的比表面积,因而表现出最高的催化活性。动力学研究结果表明,c-CuZnCr催化的反应活化能为32.73 kJ/mol,与水合肼浓度和氧气压力相关的反应级数分别为0.97和0.78。     

乳状液膜提取废汞触媒浸出液中的汞及 乳状液破乳

采用乳状液膜法分离提取废汞触媒浸出液中的Hg~(2+)。考察了影响乳状液膜体系分离富集汞的主要因素,并对分离提取后的乳液相进行了破乳研究。分离提取实验结果表明:乳状液膜体系的最佳配方为流动载体磷酸三丁酯体积分数10%、表面活性剂失水山梨糖醇脂肪酸酯体积分数4%、膜溶剂磺化煤油体积分数86%、内水相HCl溶液浓度0.10mol/L、油相与内水相的体积比1∶1;在乳状液与外水相的体积比为1∶10的条件下Hg~(2+)提取率达78.50%。破乳实验结果表明:加热破乳、离心破乳、加热离心联合破乳3种方法的破乳率分别为29.0%,54.0%,85.7%;采用加热离心联合法破乳后,Hg~(2+)富集倍数达8.5。     

NaClO2湿法烟气脱硫脱硝技术研究

介绍了NaClO2溶液湿法烟气脱硫脱硝技术的主要特点、反应机理、工艺流程，分析了NaClO2溶液湿法烟气脱硫脱硝技术的主要影响因素，并提出了该技术今后的研究方向。     

Software analyser design using data mining technology for toxicity prediction of aqueous effluents

Database and information technology has been widely used in process industries to manage data related to environmental performance. However, apart from being collected and archived for subsequent retrieval, the data has not been effectively exploited for improving environmental performance. In this paper we report our work on application of data mining and knowledge discovery technology to the analysis of a database of aqueous effluents from an organic manufacturing plant. The focus is on developing a software analyser for Microtox prediction. However, this methodology is applicable to any ecotoxicity measurement and will therefore offer a means of minimising difficult and tedious testing. Principal component analysis is used to pre-process the data for removing noise and reducing dimensionality. Automatic clustering is employed to group the multidimensional data into classes, and from each class training and testing data sets are selected for developing a back-propagation neural network to predict Microtox. The result shows that the software analyser is able to give satisfactory predictions for both training and test data. The errors for all the training and testing data are shown to satisfy a normal distribution. The software analyser is further used to carry out sensitivity studies in order to identify compounds responsible for observed toxicity value, based on which improved process operational strategies can be developed. Several approaches are investigated, including correlation coefficient analysis, sensitivity study based on differential analysis, one variable deletion, fuzzy curve approach and combination of the above with principal component analysis.     

Adsorption characteristics of Cu2+ and Zn2+ from aqueous solution using carbonized food waste

The aim of the present study was to analytically provide adsorption characteristics of Cu²⁺ and Zn²⁺ using carbonized food waste (CFW); more specifically, batch tests were conducted using various concentrations of metal ions, contact times, and initial pH levels in an attempt to understand the adsorption removal of heavy metal ions in aqueous solution at concentrations ranging between 50 and 800 mg/l. The results confirmed that the adsorption equilibrium was established within a maximum of 80 min, and the maximum concentrations for adsorption of Cu²⁺ and Zn²⁺ were 28.3 and 23.5 mg/g, respectively. These adsorption levels indicate that CFW has better performance than many other adsorbents. In experiments using different pH conditions, the applicability to acid wastewater was found to be high, and an excellent adsorption removal ratio of 75%–90% was observed under acid conditions at pH 2–4. Furthermore, as the adsorption time increased, the calcium component in the CFW began to leach into the aqueous solution and raise the pH, accordingly causing the removal of heavy metal ions partially as a result of precipitation. When our results were analyzed using the Langmuir model and the Freundlich model for isothermal adsorptivity, the activity of CFW in this study was shown to be more consistent with the former; the adsorption speed of Cu²⁺ and Zn²⁺ according to a pseudosecond-order reaction model was found to be very fast for an initial concentration of not more than 100 mg/l. In a test in which an attempt was made to compare adsorption capacity values obtained from the experiments in this study with the aforementioned three models, the pseudosecond-order reaction model was found to provide results closest to the actual values.     

Removal of Cr6 + and Ni2+ from aqueous solution using bagasse and fly ash

Raw bagasse and fly ash, the waste generated in sugar mills and boilers respectively have been used as low-cost potential adsorbents. Raw bagasse was pretreated with 0.1N NaOH followed by 0.1N CH3COOH before its application. These low-cost adsorbents were used for the removal of chromium and nickel from an aqueous solution. The kinetics of adsorption and extent of adsorption at equilibrium are dependent on the physical and chemical characteristics of the adsorbent, adsorbate and experimental system. The effect of hydrogen ion concentration, contact time, sorbent dose, initial concentrations of adsorbate and adsorbent and particle size on the uptake of chromium and nickel were studied in batch experiments. The Sorption data has been correlated with Langmuir, Freundlich and Bhattacharya and Venkobachar adsorption models. The efficiencies of adsorbent materials for the removal of Cr(VI) and Ni(II) were found to be between 56.2 and 96.2% and 83.6 and 100%, respectively. These results were obtained at the optimized conditions of pH, contact time, sorbent dose, sorbate concentration of 100 mg/l and with the variation of adsorbent particles size between 0.075 and 4.75 mm. The order of selectivity is powdered activated carbon > bagasse > fly ash for Cr(VI) removal and powdered activated carbon > fly ash > bagasse for Ni(II) removal.     

臭氧氧化结合碱液吸收法烟气脱硝的工艺研究

利用臭氧将烟气中溶解度较小的NO氧化成NO2,再结合尿素、氢氧化钠、氢氧化钙溶液吸收脱除臭氧氧化产物,重点考察了O3与NO反应的摩尔比、进口NO浓度、烟气中SO2浓度和相对湿度等工艺参数对NO氧化的影响,并探明不同的吸收液脱除臭氧氧化产物的特性。结果显示O3与NO反应的最佳摩尔比为1.02,随着进口NO浓度的增加氧化效率下降,而烟气中的SO2和相对湿度对NO氧化影响较小。通过对氢氧化钙吸收臭氧氧化产物的特性分析得出,碱液对NO的吸收率相对较小,而对NO2的吸收率达到80%以上。