利用一氧化碳工业废气解毒铬渣的方法及条件优化

结合铬渣解毒及一氧化碳工业废气利用现状,提出采用一氧化碳工业废气解毒铬渣的方法。实验对反应温度、反应时间、铬渣质量、铬渣粒径等影响因素进行研究和筛选,用响应面法(RSM)分析了各因素对反应的影响及各因素之间交互性,建立反应的多元回归方程,并通过热力学分析进一步研究方法优越性的机理。结果表明:温度是该工艺铬渣解毒效率的关键影响因素,反应温度越高,解毒效果越好,优选反应温度范围350~400℃;浸出毒性目标值设定为1.0 mg·L~(-1),反应温度为400℃,铬渣质量为40 g,浸出毒性可降低至0.6 mg·L~(-1),还原率达99.85%;多元回归方程拟合性验证结果良好,RSM分析方法在条件优化中有较好的实用价值。     

铬污染场地渣土混合物的化学还原修复

针对目前铬污染场地表层重污染铬渣混土难处理的问题,选用河南义马某铬盐厂铬渣堆场表层渣土混合物为研究对象,在分析其理化特性的基础上,研究CaS_4、FeSO_4·7H_2O和葡萄糖3种还原药剂对Cr(VI)的还原效率,通过改变药剂投加量、反应体系pH、反应时间等条件,优化修复工艺参数。结果表明,3种还原药剂对渣土混合物的最佳还原效率大小为CaS_4(98.50%)FeSO_4·7H_2O(72.21%)葡萄糖(51.45%)。CaS_4还原修复渣土混合物的最优工艺参数为:药剂投加量为还原反应理论当量的2倍,体系pH在3～9,反应时间0.5 h。     

基于复合球团的以生物质焦油为还原剂的铬渣无害化处理

结合目前铬渣解毒现状,提出生物质焦油热解还原铬渣的新技术,利用生物质气化副产物焦油作为解毒剂,进而提高铬渣解毒和资源化水平,降低能耗。将生物质焦油和铬渣混合制成球团通过热解实现Cr(VI)向Cr(III)的形态转化,对影响焦油热解还原铬渣的主要因素:温度、铬渣粒径、球团尺寸、铬渣与焦油当量比等进行探讨。结果表明:还原铬渣的质量随温度升高而提高,温度超过400℃后无明显变化,减小铬渣粒径与球团尺寸可明显提高还原质量。当热解温度为400℃,还原时间10 min,铬渣与焦油当量比2.29,铬渣粒径0.074 mm,球团粒径2.5 mm时,可得到Cr(VI)还原率98.65%的还原铬产品。     

铬渣冷固结球团的还原实验及其解毒机理

铬渣中六价铬对人体和生态环境都有严重的危害,必须进行处理。在铬渣加入粘结剂、煤粉或铁精矿粉制成冷固结球团,在一定温度下进行还原解毒。实验表明,在1200℃以下用煤气铬渣球团,铬渣基本解毒;在1400℃熔炼还原后的铬渣球团,可使铬全部还原成金属铬或Cr7C3,在铁碳化合物存在的情况下,可形成(Fe·Cr)7C3,铬渣彻底解毒,并能回收铬渣中的Cr、Fe等元素。故可将铬渣制成冷固结球团进行还原解毒,进行高温熔炼后,可达到铬渣无害化、资源化处理。     

铬渣的热解无害化处理

采用热解工艺无害化处理铬渣,探讨了稻秆在铬渣无害化处理中的作用.研究了热解温度、稻秆与铬渣质量比、铬渣粒径及保温时间对铬渣热解无害化处理的影响,并分析了热解前后热解产物中铬元素形态的变化.结果表明,热解工艺能有效地将铬渣中Cr(Ⅵ)还原,稻秆热解过程中产生的气相挥发分对Cr(Ⅵ)的还原起核心作用.较为适宜的热解条件:热解温度为400 ℃,稻秆与铬渣质量比为0.10,铬渣粒径<2 000 μm,保温时间为10 min.在该热解条件处理下,热解产物中的Cr(Ⅵ)质量浓度为121 mg/kg,低于热解前铬渣中的Cr(Ⅵ)(3 400 mg/kg).热解后,可交换态及碳酸盐结合态铬含量降低,大部分铬转化成了稳定的有机结合态和残渣态,极大地降低了铬渣的危害.第一作者:张大磊,男,1982生,博士研究生,研究方向为固体废弃物热处理.     

铬渣酸溶性六价铬浸出动力学研究

考察了铬渣中的六价铬的在硫酸中浸出行为,分别研究了温度、硫酸浓度和铬渣粒径对酸溶性六价铬浸出的影响.研究表明,酸溶性六价铬酸浸为化学反应过程,可用"颗粒不变缩核收缩芯模型"进行描述,通过尝试法,确定酸溶性六价铬浸出过程为内扩散控制类型,表观活化能为9.32 kJ/mol;在此基础上,经多元回归分析,得到了表观反应速率常数关于温度、硫酸浓度和铬渣粒径的经验表达式.     

Cr(Ⅵ)污染土壤的热解还原无害化处理

提出了用热解还原法对含铬土壤进行无害化处理的新技术,研究了热解温度、热解时间及土壤有机质对铬无害化处理的影响,分析了热解前后土壤中铬的元素形态的变化.同时还探讨了热解还原过程中Cr(Ⅵ)的无害化机制.结果表明,土壤中的有机质在热解还原过程中产生的挥发分对Cr(Ⅵ)的无害化起核心作用;在200～600℃范围内,Cr(Ⅵ)的还原量随着热解温度升高而增大,500.0℃最适合于经济有效地实现Cr(Ⅵ)的热解还原处理;Cr(Ⅵ)的热解还原过程较快.铬的形态分析结果表明,热解后可交换态和碳酸盐结合态铬量大大降低,大部分铬转化成了活性低的残渣态,极大地降低了铬的危害.     

铬渣秸秆共热解产物铬稳定性研究

生物质铬渣共热解工艺是新型的铬渣处理工艺,该工艺能有效地将铬渣中的Cr(Ⅵ)还原为Cr(Ⅲ).而由于共热解产物总铬含量较高,因此考察了铬渣与秸秆共热解过程中铬稳定性.通过考察共热解产物成分及形态分析、pH影响实验、淋洗实验及长期稳定性实验,对共热解铬渣的铬环境安全性进行评估.结果表明:(1)共热解温度对铬渣形态有较大影响,可交换态及碳酸盐结合态铬含量随共热解温度升高而逐渐降低,800℃时候可交换态铬降至＜0.1％(质量分数,下同),碳酸盐结合态铬为1.2％;共热解后最稳定的残渣态铬含量随共热解温度升高而逐渐升高.(2)当pH＞7时,两种共热解产物总铬溶出量极低,基本都小于6mg/kg;当pH≤7时,总铬的溶出量显著增加,最高超过500 mg/kg.但由于解毒铬渣的酸中和能力极强,因此铬释放风险较低.(3)共热解产物的总铬累积溶出量极低,根据拟合结果计算出其100年填埋时间的总铬溶出量不超过1.3 mg/kg.长期稳定性实验表明,自然堆置过程中共热解产物的Cr(Ⅵ)含量逐渐降低.     

铬渣的高温-快冷-等温转变固化研究

采用高温-快冷-等温转变对铬渣进行固化处理,通过调整配料成分确定最高固化温度,使铬渣的处理量最大且软化温度最低,以利节能和实际工业应用。结果显示,混合物以含铬渣35％～40％、粘土35％～45％、河沙10％、粉煤灰10％时,软化温度最低为1120～1125℃,固化产物经过标准毒性浸出,所测定的浸出液六价铬离子浓度低于0．8mg／L。该固化方法具有操作流程较短、铬渣处理量大等优点,可成功固化其中的六价铬离子。其固化原理是铬渣中铬离子在高温下迁移至相界面,在合理的冷却过程中稳定存在于相界面,而不易被浸出。     

磷石膏还原分解反应热力学分析

磷石膏是高浓度磷肥工业排放的固体废弃物,采用HSC Chemistry 5热力学计算软件对焦炭、硫磺、氢气、一氧化碳与磷石膏还原反应进行了对比分析,探索如分解温度、平衡常数、耗能与还原介质的关系。结果表明,不论采用上述何种还原介质,CaSO4还原分解成CaS均比CaO容易进行。     

Catalytic wet oxidation of the pretreated synthetic pulp and paper mill effluent under moderate conditions

In the present study, catalytic wet oxidation (CWO) was investigated for the destruction of organic pollutants in the thermally pretreated effluent from a pulp and paper mill under moderate temperature and pressure conditions. The thermal pretreatment studies were conducted at atmospheric pressure and 368K using copper sulfate as a catalyst. The thermal pretreatment reduced COD by about 61%. The filtrate of the thermal pretreatment step was used at pH 8.0 for CWO at 383-443K temperature and a total pressure of 0.85MPa for 4h. Catalysts used for the reaction include copper sulfate, 5% CuO/95% activated carbon, 60% CuO/40% MnO(2), and 60% CuO/40% CeO(2). Maximum COD reduction was found to be 89% during CWO step using 5% CuO/95% activated carbon with a catalyst loading of 8gl(-1) at 443K and 0.85MPa total pressure. Overall COD reduction for the pretreatment and the CWO was found to be 96%. Besides this, 60% CuO/40% CeO(2) catalyst also exhibited the similar activity as that of obtained with 5% CuO/95% activated carbon catalyst at 423K temperature and 0.85MPa total pressure. The pH of the solution during the experimental runs decreases initially due to the formation of carboxylic acid and then increases due to the decomposition of acids.     

零价铁对土壤中2-氯硝基苯的还原作用

在常温常压下利用零价铁(Fe0)还原土壤中的2-氯硝基苯(o-CNB),研究反应条件对还原率的影响以及反应产物在不同反应阶段的变化.GC-MS检测结果显示,o-CNB在还原过程中先生成2-氯亚硝基苯,最终生成2-氯苯胺.反应时间、Fe0用量、温度和土壤初始pH值等均会对o-CNB的还原率产生影响,其中土壤初始pH值控制在偏酸性、土壤温度较高时能显著提高其还原率.当o-CNB的初始浓度约为2.5×10-6 mol/g,Fe0加入量是25 mg/g时,经过4 h反应,o-CNB的还原率可达99%以上.此外,还初步探讨了Fe0还原o-CNB的反应机理.     

纳米零价铁的制备及其去除水中对氯硝基苯的研究

通过FeSO4与KBH4反应,利用液相还原法制备纳米零价铁颗粒(NZVI),用XRD、SEM和BET对其性能进行表征。在常温常压下利用纳米铁还原废水中的对氯硝基苯(p-CNB),探讨了反应条件对还原率的影响。结果表明,制备过程中碱性物质(NaOH)的添加可以明显减小颗粒粒径,增大比表面积,提高纳米铁还原反应的效率。NZVI对于对氯硝基苯有很好的去除效果,NZVI用量、p-CNB初始浓度和pH值均对其去除效率产生影响。在纳米铁投加量为1 g/L,pH=2的条件下,添加NaOH的纳米铁能在120 min内将质量浓度为50 mg/L的对氯硝基苯基本完全降解,降解率为98.8%。此外,还对NZVI还原对氯硝基苯的机理进行了初步探讨。     

Modeling solubility of CO<Subscript>2</Subscript>/hydrocarbon gas in ionic liquid ([emim][FAP]) using Aspen Plus simulations

The Peng-Robinson equation of state with quadratic van der Waals (vdW) mixing rule model was chosen to perform the thermodynamic calculations in Flash3 column of Aspen Plus to predict the solubility of CO₂ or any one of the hydrocarbons (HCs) among methane, ethane, propane, and butane in an ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([emim][FAP]). Bubble point pressure, solubility, bubble point temperature, fugacity, and partial molar volume at infinite dilution were obtained from the simulations, and enthalpy of absorption, Gibbs free energy of solvation, and entropy change of absorption were estimated by thermodynamic relations. Results show that carbon chain length has a significant effect on the bubble point pressure. Methane has the highest bubble point pressure among all the considered HCs and CO₂. The bubble point pressure and fugacity variation with temperature is different for CO₂ as compared to HCs for mole fractions above 0.2. Two different profiles are noticed for enthalpy of absorption when plotted as a function of mole fraction of gas soluble in IL. Partial molar volume of CO₂ decreases with increase in temperature in [emim][FAP], while it is increased for HCs. Bubble point temperature decreases with increase in the mole fraction of the solute. Entropy of solvation increases with temperature till a particular value followed by a decrease with further increase in temperature. Gibbs free energy change of solvation showed that the process of solubility was spontaneous.     

Biogeochemistry and isotope geochemistry of a landfill leachate plume

The biogeochemical processes were identified which improved the leachate composition in the flow direction of a landfill leachate plume (Banisveld, The Netherlands). Groundwater observation wells were placed at specific locations after delineating the leachate plume using geophysical tests to map subsurface conductivity. Redox processes were determined using the distribution of solid and soluble redox species, hydrogen concentrations, concentration of dissolved gases (N(2), Ar, and CH(4)), and stable isotopes (delta15N-NO(3), delta34S-SO(4), delta13C-CH(4), delta2H-CH(4), and delta13C of dissolved organic and inorganic carbon (DOC and DIC, respectively)). The combined application of these techniques improved the redox interpretation considerably. Dissolved organic carbon (DOC) decreased downstream in association with increasing delta13C-DOC values confirming the occurrence of degradation. Degradation of DOC was coupled to iron reduction inside the plume, while denitrification could be an important redox process at the top fringe of the plume. Stable carbon and hydrogen isotope signatures of methane indicated that methane was formed inside the landfill and not in the plume. Total gas pressure exceeded hydrostatic pressure in the plume, and methane seems subject to degassing. Quantitative proof for DOC degradation under iron-reducing conditions could only be obtained if the geochemical processes cation exchange and precipitation of carbonate minerals (siderite and calcite) were considered and incorporated in an inverse geochemical model of the plume. Simulation of delta13C-DIC confirmed that precipitation of carbonate minerals happened.     

Influence of temperature and time on phosphorus removal in swine manure during batch aeration

This study was conducted to investigate the effects of temperature and time on the mechanisms of phosphorus removal in swine manure during aeration. Removal of soluble orthophosphates significantly increased with aeration time and temperature. Successive significant ortho-P removals were observed between days one and nine but no significant additional removals were recorded thereafter. Removals were significantly higher at temperatures of 20 and 25 degrees C than at temperatures of 5, 10, and 15 degrees C and ranged between 22.9 to 31.0%. Insoluble inorganic phosphorus also changed significantly with aeration time and temperature and with a similar trend as soluble orthophosphates. The pH of the manure explained 92 and 87% of the content of insoluble inorganic phosphorus at lower temperatures (5, 10, 15 degrees C) and at higher temperatures (20, and 25 degrees C), respectively. Organic phosphorus and aerobes growth patterns were similar to that of soluble orthophosphates removal. The rapid growth of aerobes was most probably the principal factor behind a rapid soluble ortho-P removal above 15 degrees C. The contribution of inorganic phosphates to the removal of soluble orthophosphates was approximately 61% while that due to organic P was approximately 35%. Precipitation was found to be the principal mechanism governing removal of soluble ortho-P in swine manure during aeration treatments.     

Improved solubilization of activated sludge by ozonation in pressure cycles

The generation of a large volume of activated sludge (AS) from wastewater treatment has increasingly become a great burden on the environment. Anaerobic digestion is routinely practiced for excess waste sludge; however, the process retention time is long because of kinetic limitation in the hydrolysis step. We tested the feasibility of applying ozone in pressure cycles to enhance the disintegration and solubilization of AS with the goal to prepare them for digestion using reduced ozone dose and contact time. The AS was subjected to repetitive pressure cycles in a closed vessel in which an ozone gas mixture was compressed into the slurry to reach 1040 kPa in the headspace to be followed by rapid venting. For a returned AS with total COD (tCOD) of 8200 mg L(-1), a dose of 0.01 gO(3)g(-1) total suspended solids (TSS) delivered via 20 pressure cycles within 16 min resulted in a 37-fold increase of the sCOD/tCOD ratio (due to increased soluble COD, i.e. sCOD) and a 25% reduction of TSS, in comparison to a dose of 0.08 gO(3)g(-1) TSS via bubbling contact over 15 min that resulted in a 15-fold increase of the sCOD/tCOD ratio and a 12% reduction of TSS. Sludge solubilization was evidenced by increased dissolved contents of total phosphorous (from 10 to 64 mg L(-1)), total nitrogen (from 14 to 120 mg L(-1)), and protein (from <15 to 39 mg L(-1)) in the sludge suspension after treatment, indicating significant solubilization of AS.     

Solubilization of blood meal to be used as a liquid fertilizer

The solubilization of blood meal by means of the microwave-hydrogen peroxide enhanced advanced-oxidation process (MW/H(2)O(2)-AOP) was studied. It was found that over the treatment temperature range of 60 to 120 degrees C, solids particle reduction, ammonia and orthophosphate production could be achieved by this process. Large protein molecules were broken down into intermediate compounds with low molecule weights, ammonia and nitrate. Intermediate compounds, such as peptides and amino acids, can also be easily converted to nitrogenous nutrients for plant growth by bacteria. Soluble nitrogen content increased with an increase in microwave heating temperature when acid was added; significant amounts of ammonia were obtained at higher temperatures. Nitrate decreased in concentration with an increase of treatment temperature. Orthophosphate concentrations increased after the advanced-oxidation process (AOP) treatments, with and without acid addition; but were more pronounced with acid addition. Maximum solubility of chemical oxygen demand (COD) occurred at 80 degrees C. Without the addition of acid, soluble COD decreased due to protein denaturation and coagulation out of the solution.     

失效锂离子电池材料真空热处理及氨性浸出

研究了失效锂离子电池中塑料、电极隔膜等有机物的真空脱除,并以电池级纯钴酸锂(LiCoO2)为原料,与活性炭粉混合,在真空中进行热还原,还原产物用含NH3和NH4HCO3的氨性水溶液浸出。实验结果表明,当加热温度大于450℃,真空压力<400 Pa时,失效锂离子电池中有机挥发物基本被脱除。在400℃真空温度下纯LiCoO2不被炭粉还原;当还原温度达到600℃,LiCoO2转变为CoO、Co和Li2CO3;在800℃时,还原产物主要为六方相、立方相金属钴及少量的CoO。还原产物中的钴易于被氨性水溶液浸出,浸出3 h后,钴基本进入溶液中,锂的浸出率也达到97%以上。     

Characterizing kinetics of transport and transformation of selenium in water-sediment microcosm free from selenium contamination using a simple mathematical model

This study developed a seven-compartment model for predicting the fate of selenium (Se) in an aquatic environment containing a water-sediment boundary. Speciation of Se in water-sediment microcosms under microaerobic conditions was measured to evaluate first-order kinetics of Se transportation and transformation. The microcosm consisted of a 10-ml solution containing 1mM soluble Se as selenate (Se6+) or selenite (Se4+) and 8 g wet sediment that was free from Se contamination, sampled from the Senri, Yamato, or Yodo Rivers in Osaka, Japan. Stepwise reaction coefficients describing transportation and transformation were determined using an inverse method on this model which includes: selenate (Se(W)6+) and selenite (Se(W)4+) in ponded water; selenate (Se(S)6+) and selenite (Se(S)4+), elemental Se (Se0), organic Se (Se2-) in sediment; and gaseous Se (DMSe). During this 1-month experiment, soluble Se was transported from ponded water to the sediment and Se was transformed sequentially to other Se species through biochemical reactions. Experimental and kinetic analyses indicated quantitatively that the Yamato River microcosm, with its high organic matter content, had a high adsorption rate of soluble Se. The Yodo River microcosm had a low adsorption rate for Se6+ and a low Se reduction rate. The Senri River microcosm had an apparent high volatilization rate of DMSe. The model developed in this study is extremely useful for predicting fate of Se in aquatic environment in the field.