Removal of Eu3+, Ce3+, Sr2+, and Cs+ ions from radioactive waste solutions by modified activated carbon prepared from coconut shells

As a biomass agricultural waste material, coconut shells were used for the preparation of high-quality modified activated carbon. Chemical modification of the surface of the prepared activated carbon is done by oxidation using H₂O₂ and HNO₃, respectively. The surface area and pore volume of the coconut shells activated carbon are increased by the chemical modification, and followingly the removal of the metals is improved. The structural morphology and composition of the modified activated carbon coconut shells (MACCS) were evaluated by Fourier transform infrared (FTIR) spectra, thermogravimetric analysis–differential thermal analysis (TGA-DTA), scanning electron microscope (SEM), X-ray diffraction (XRD), surface area analysis (SAA), X-ray fluorescence (XRF), and carbon, hydrogen, nitrogen, and sulfur (CHNS) elemental analysis. The prepared MACCS has reasonably good chemical stability. The influence of solution pH, contact time, adsorbent dosage, adsorption temperature, initial metal concentrations, and interfering ions on the adsorption performance of the investigated ions onto the prepared sorbent was examined by a batch method. The selectivity sequence for sorption of Eu³⁺, Ce³⁺, Sr²⁺, and Cs⁺ ions on MACCS was found to be Eu^3+?>?Ce^3+?>?Sr^2+?>?Cs⁺. The saturation capacities of MACCS for the studied metal ions were found to be 136.84, 85.55, 69.85, and 60.00?mg?g^?1 for Eu³⁺, Ce³⁺, Sr²⁺, and Cs⁺ ions, respectively. The thermodynamic parameters, ΔH°, ΔS°, and ΔG° were also evaluated.     

Monitoring of soil biochemical quality parameters under greenhouse spinach cultivation through animal waste recycling

Under the intensive agricultural system, direct application of animal slurries to soils can provide a sustainable disposal of these wastes by inducing positive changes in soil quality and fertility. However, how animal wastes quantitatively affect the key nutrients (C, N, P and S) transforming soil enzymes is not clearly known. A greenhouse spinach cultivation study demonstrated that pig slurry, either in raw (RS) or processed (aerobically aged) (PS) form, significantly (p?β-glucosidase (23–39%), urease (59–103%), nitrate reductase (73–103%) and dehydrogenase (27–72%)) and microbial growth in soil as compared to the unamended control. However, it did not significantly (p?>?.05) alter the aryl sulphatase enzyme activity. Slurry applications also significantly improved the macro (N, P and K) and micronutrients (Cu, Mn, Zn and Fe) uptake by spinach plant and hence the yield (2.9–3.38 times higher than control). Similarly, compared to chemical fertilisers the application of pig slurries improved soil biological and biochemical parameters as well as plant nutrients uptake. This study demonstrated the closing of global energy and nutrient cycles through land application of animal wastes without compromising the crop yield.     

Life cycle assessment of food waste home composting in Greece

Home composting is a waste prevention measure related to the management of the household's food waste, garden trimmings, and other smaller organic household waste streams. Thus, home composting is an alternative way of exploitation of the “biomass” generated from the households. It is an alternative to centralized composting. Biomass utilization is explicitly stated as a principle of green chemistry. The aim of this paper is presentation of the results of a case study dealing with the life cycle environmental assessment of home composting of food waste in households in Greece. The results of the study indicate that home composting is environmentally preferable over the current organic waste management situation in Greece.     

Characteristics of the stabilized/solidified municipal solid wastes incineration fly ash and the leaching behavior of Cr and Pb

Fly ash is a hazardous byproduct of municipal solid wastes incineration (MSWI). An alkali activated blast furnace slag-based cementitious material was used to stabilize/solidify the fly ash at experimental level. The characteristics of the stabilized/solidified fly ash, including metal leachability, mineralogical characteristics and the distributions of metals in matrices, were tested by toxic characteristic leaching procedure (TCLP), X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) respectively. Continuous acid extraction was utilized to extract metal ions and characterize their leaching behavior. The stabilization/solidification procedure for MSWI fly ash demonstrates a strong fixing capacity for the metals by the formation of C-S-H phase, hydrated calcium aluminosilicate and ettringite. The stabilized/solidified fly ash shows a dense and homogeneous microstructure. Cr is mainly solidified in hydrated calcium aluminosilicate, C-S-H and ettringite phase through physical encapsulation, precipitation, adsorption or substitution mechanisms, and Pb is mainly solidified in C-S-H phase and absorbed in the Si-O structure.     

Environment and economic feasibility of municipal solid waste central sorting strategy: a case study in Beijing

Although Beijing has carried out municipal solid waste (MSW) source separation since 1996, it has largely been ineffective. In 2012, a “Green House” program was established as a new attempt for central sorting. In this study, the authors used material flow analysis (MFA) and cost benefit analysis (CBA) methods to investigate Green House’s environment and economic feasibility. Results showed that the program did have significant environmental benefits on waste reduction, which reduced the amount of waste by 34%. If the Green House program is implemented in a residential community with wet waste ratio of 66%, the proportion of waste reduction can reach 37%. However, the Green House is now running with a monthly loss of 1982 CNY. This is mainly because most of its benefits come from waste reduction (i.e., 5878 CNY per month), which does not turn a monetary benefit, but is instead distributed to the whole of society as positive environmental externalities. Lack of government involvement, small program scale, and technical/managerial deficiency are three main barriers of the Green House. We, thus, make three recommendations: involve government authority and financial support, expand the program scale to separate 91.4 tons of waste every month, and use more professional equipment/technologies. If the Green House program can successfully adopt these suggestions, 33.8 tons of waste can be reduced monthly, and it would be able to flip the loss into a profit worth 35034 CNY.

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稳定剂对电解锰废渣中高浓度可溶性锰稳定效果的影响

为满足大宗废渣经济性处理的需要,从碱性物质、磷酸盐、碳酸盐类药剂筛选出“物美价廉”稳定剂,考察了CaO、MgO和Ca10(PO4)6(OH)2及其与NaHCO3和Na3PO4的组合对电解锰废渣中的可溶性锰的稳定化效果,并采用矿物组成分析、锰价态分析和形态变化探讨可溶性锰固定机理.结果表明:投加10%MgO锰渣中可溶性锰固定率达到100%,9%CaO+5%NaHCO3和9%CaO+5%Na3PO4的组合实现可溶性锰固定率95%以上.上述3组稳定剂将可溶性Mn2+先转变为沉淀态锰进一步转变为高价态含锰物相.后两组中NaHCO3或Na3PO4的加入促进了Mn2+向Mn3+、Mn4+的转化.     

两阶段评估体系筛选水源突发污染应急最优技术方案

为预判突发污染对水源的威胁程度,进而筛选适宜污染情景的最优应急处置技术,本研究构建了包含10个评价指标的水源突发污染威胁度判别指标体系,依据威胁度等级判定,确定与不同威胁度对应的应急处置技术评估指标体系的指标权重.同时,为合理体现群决策过程中专家差异对权重的影响,提出了基于循环修正的群组G1指标赋权法.以Spearman等级相关系数作为检验标准,应用平均值法、Board法、Copeland法3种组合评价方法对单一专家评价结果进行循环迭代修正,最终得到评价指标的一致性排序和各位专家的权重,使各项指标的权重赋值更为准确.将综合评估模型应用于2012年广西龙江镉污染事故中,成功筛选出“调水稀释—絮凝沉降—水厂强化混凝”的组合应急技术方案,同实际情况吻合,验证了评估模型的可行性.     

湿热水解预处理对餐厨废弃物液相物质转化的影响

设计湿热水解预处理温度(80、120、150和200 ℃)、时间(40、50、60和70 min)、加水量(40%、60%、80%和100%)的三因素四水平正交试验,研究湿热水解预处理对餐厨废弃物液相可浮油脱出量、ρ(COD_Cr)、糖类、ρ(VFA)(VFA为挥发性脂肪酸)等的影响. 结果表明:餐厨废弃物经湿热水解预处理后可浮油脱出量明显提高. 在150 ℃、加水量40%、处理60 min的湿热水解条件下,可浮油脱出量(67.7 mL/kg)最高,比未经预处理的对照组提高了2.65倍;同时,ρ(还原糖)和ρ(总糖)也达到最高,分别比对照组增加了16.29%和38.92%.随着温度升高和处理时间的延长,ρ(COD_Cr)不断升高,在200 ℃、加水量40%、处理70 min的湿热水解条件下,ρ(COD_Cr)最高为109.729 g/L,比对照组提高了1.39倍. 经湿热水解预处理后,ρ(VFA)也呈显著增加,在200 ℃、加水量100%、处理40 min的湿热水解条件下,ρ(VFA)达到最高,比对照组增加了66.26%.预处理后,ρ(乙酸)、ρ(丁酸)升高,ρ(乙醇)降低. 方差、极差综合分析表明,在湿热水解过程中,温度是影响餐厨废弃物液相物质转化的主控因子,其次是加水量和时间.      

输氧抽气技术在垃圾填埋场治理中的关键参数试验研究

输氧抽气技术是基于好氧降解原理对垃圾填埋场中固体废弃物实施原位处理的先进环保技术。采用该技术对垃圾填埋场中固体废弃物减量化研究,总结了技术应用中的关键参数:有效影响半径,最佳真空度等。结果表明抽气流量大小与影响半径密切相关,抽气影响半径建议取20~25 m,抽气系统最优负压为20 k Pa,同时在技术应用过程中应保证垃圾场表层覆盖层的密封性能,尽量减少空气的渗入。输氧抽气技术在垃圾场的成功实施为同类型场地治理提供工程技术参考。     

水溶性吸收剂对甲苯废气的吸收性能

液体吸收法应用于处理工业有机废气涉及到2个关键因素,即吸收剂的选择与吸收液的再生处理. 选择8种水溶性吸收剂——2种氟碳表面活性剂(FSO100和FSN100)、2种非离子表面活性剂〔TW80(吐温80)和SP20(斯盘20)〕、2种阴离子表面活性剂〔脂肪醇聚氧乙烯醚硫酸钠(AES)和脂肪醇聚氧乙烯醚羧酸钠(AEC)〕及2种类表面活性剂〔β-CD(β-环糊精)和SA(乙酸钠), 对模拟甲苯废气进行了动力学吸收试验,研究吸收性能和加热蒸馏法对甲苯回收与吸收剂溶液再生的可行性. 结果表明:吸收剂类型是影响甲苯吸收能力的最主要因素. 2种氟碳表面活性剂吸收液的甲苯吸收能力最强,其次是SP20与AES,而其他4种吸收剂溶液对甲苯的吸收能力很弱. 上述3类吸收剂对甲苯的初始去除率分别为80%～90%、75%左右与60%～70%,甲苯饱和吸收浓度(以w计)分别为0.58～3.45、0.38～1.44与0.14～1.01 mg/g. 除TW80吸收液热稳定性差、不宜采用加热蒸馏方法再生外, 其他吸收剂溶液经5次重复使用,甲苯回收率可达70%～85%,并能保持其原有吸收性能. 甲苯分配系数计算结果表明,FSO100和FSN100分别为0.41、0.62, SP20和AES分别为0.76、0.95, 其他4种吸收剂溶液在1.12～3.54之间;甲苯分配系数与饱和吸收浓度呈负相关、与体积传质系数呈正相关. 因此,2种氟碳表面活性剂吸收液对甲苯的吸收能力强,加热蒸馏法回收甲苯与再生吸收液具有经济性,用于处理甲苯废气具有广泛的应用前景.