Conversion of chromium-containing solid wastes into value-added products through a plasma-assisted aluminothermic process

Chromium-containing solid wastes have been generated by chemical and leather/tanning industries, and the management and proper disposal of the same wastes have been challenging tasks. A significant fraction of these wastes contains chromium compounds with chromium present in the hexavalent (Cr⁺⁶) form, which is hazardous to human beings, animals, and ecosystems. Since these wastes are discarded largely without proper treatments, soil and groundwater get contaminated and they can cause several health issues to human beings. Conventional methods developed to convert hazardous Cr⁶⁺ to Cr³⁺/Cr metal either generate secondary toxic wastes and unwanted by-products and/or are time-consuming processes. In this work, a plasma-assisted aluminothermic process is developed to convert the toxic waste into non-toxic products. The waste was mixed with aluminium powder and subjected to transferred arc plasma treatment in a controlled air atmosphere. Chemical analysis and Cr leachability studies of the waste material prior to plasma treatment have shown that it is highly toxic. Analysis of the products obtained from the plasma treatment showed that Cr and Fe present in the waste could be recovered as a metallic mixture as well as oxide slag, which were found to be non-toxic. Easy separation of the metallic fraction and the slag from the treated product is one of the merits of this process. Besides converting chromium-containing toxic waste to non-toxic materials, the process is rapid and recovers the metals from the waste completely.

     

选矿技术在城市固体废弃物资源化中的应用

选矿技术作为一种成熟的矿物分离技术已广泛应用于城市固体废弃物资源化领域 ,促进了环境的保护和资源的综合回收 ;同时也开辟了选矿技术新的应用领域。结合实例介绍国内外常用的各种城市固体废弃物的分选工艺 ,指出选矿技术的运用对固体废弃物的资源化有着重要的实际意义     

湿热水解处理餐厨垃圾氮素转化规律

为了研究餐厨垃圾湿热水解过程中氮素的变化规律,设计了10、30、60、90和120℃5个温度水平以及30、60、90、120、150和180min6个加热时间水平,进行了30组完全实验,对不同湿热条件下餐厨垃圾粗蛋白、TN、NH4＋-N、NO3-N、有机氮及氨基酸等氮的不同存在形式的变化规律进行实验研究。结果表明,10、30及60℃条件下蛋白质的高级结构不会改变,利于粗蛋白的积累,且在温度120℃,加热时间90min条件下粗蛋白百分含量最高,占干物质的31．34％;随温度的升高和加热时间的延长TN、NHf-N和有机氮含量均上升;当温度达到120℃,由于水解反应,各温度处理下NHf．N浓度超过有机氮浓度,而NO3-N始终维持较低水平。氨基酸总量随温度的升高和水解时间的延长呈上升趋势,当温度达90％,加热时间达180min时,处理后餐厨垃圾总氨基酸百分含量最高,达164％,但温度达到120℃时,随着处理时间的延长,餐厨垃圾总氨基酸含量明显降低。     

Activated carbon amendment to sequester PAHs in contaminated soil: a lysimeter field trial

Activated carbon (AC) amendment is an innovative method for the in situ remediation of contaminated soils. A field-scale AC amendment of either 2% powder or granular AC (PAC and GAC) to a PAH contaminated soil was carried out in Norway. The PAH concentration in drainage water from the field plot was measured with a direct solvent extraction and by deploying polyoxymethylene (POM) passive samplers. In addition, POM samplers were dug directly in the AC amended and unamended soil in order to monitor the reduction in free aqueous PAH concentrations in the soil pore water. The total PAH concentration in the drainage water, measured by direct solvent extraction of the water, was reduced by 14% for the PAC amendment and by 59% for GAC, 12 months after amendment. Measurements carried out with POM showed a reduction of 93% for PAC and 56% for GAC. The free aqueous PAH concentration in soil pore water was reduced 93% and 76%, 17 and 28 months after PAC amendment, compared to 84% and 69% for GAC. PAC, in contrast to GAC, was more effective for reducing freely dissolved concentrations than total dissolved ones. This could tentatively be explained by leaching of microscopic AC particles from PAC. Secondary chemical effects of the AC amendment were monitored by considering concentration changes in dissolved organic carbon (DOC) and nutrients. DOC was bound by AC, while the concentrations of nutrients (NO(3), NO(2), NH(4), PO(4), P-total, K, Ca and Mg) were variable and likely affected by external environmental factors.     

Zn biomineralization processes and microbial biofilm in a metal-rich stream (Naracauli,Sardinia)

Several decades after the closure of the Ingurtosu mine (SW Sardinia), a variety of seasonal Zn biomineralizations occurs. In this work, waters, microbial consortia, and seasonal precipitates from the Naracauli stream were sampled to investigate chemical composition of stream waters and biominerals, and microbial strain identity. Molecular and morphological analysis revealed that activity of dominant cyanobacterium Leptolyngbya frigida results in precipitation of Zn silicate. The activity of the cyanobacterium was associated to other bacteria and many kind of diatoms, such as Halamphora subsalina and Encyonopsis microcephala, which are trapped in the process of biomineral growth. In this work, the precipitation process is shown to be the result of many different parameters such as hydrologic regime, microbial community adaptation, and biological mediation. It results in a decrease of dissolved Zn in the stream water, and is a potential tool for Zn pollution abatement.     

钙化物在废弃物基活性炭制备过程中的影响

研究了以城市垃圾中3种典型的固体有机废弃物——锯木屑、纸张和塑料的热解产物(分别简称木炭、纸炭和塑料热解物)为原料,水蒸气为活化剂制备废弃物基活性炭时钙化物含量对活化过程、活性炭吸附性能(以碘值表征)及其孔结构的影响。结果表明,钙化物可加快活化反应的速度,且钙化物含量在1.5％时活化反应速度即已不再随钙化物含量的增加而增加;活性炭的吸附性能则随钙化物含量的增加而减少,同时钙化物对活性炭的孔径分布基本无影响,但降低了活性炭的比表面积、微孔孔容及中孔孔容;钙化物的2种前驱体（即CaO和Ca(OH)₂）对活化过程具有相同的催化作用。     

Effluent trading in river systems through stochastic decision-making process: a case study

Environmental Science and Pollution Research - The objective of this paper is to provide an efficient framework for effluent trading in river systems. The proposed framework consists of two...     

Emerging trends in photodegradation of petrochemical wastes: a review

Various human activities like mining and extraction of mineral oils have been used for the modernization of society and well-beings. However, the by-products such as petrochemical wastes generated from such industries are carcinogenic and toxic, which had increased environmental pollution and risks to human health several folds. Various methods such as physical, chemical and biological methods have been used to degrade these pollutants from wastewater. Advance oxidation processes (AOPs) are evolving techniques for efficient sequestration of chemically stable and less biodegradable organic pollutants. In the present review, photocatalytic degradation of petrochemical wastes containing monoaromatic and poly-aromatic hydrocarbons has been studied using various heterogeneous photocatalysts (such as TiO₂, ZnO and CdS. The present article seeks to offer a scientific and technical overview of the current trend in the use of the photocatalyst for remediation and degradation of petrochemical waste depending upon the recent advances in photodegradation of petrochemical research using bibliometric analysis. We further outlined the effect of various heterogeneous catalysts and their ecotoxicity, various degradation pathways of petrochemical wastes, the key regulatory parameters and the reactors used. A critical analysis of the available literature revealed that TiO₂ is widely reported in the degradation processes along with other semiconductors/nanomaterials in visible and UV light irradiation. Further, various degradation studies have been carried out at laboratory scale in the presence of UV light. However, further elaborative research is needed for successful application of the laboratory scale techniques to pilot-scale operation and to develop environmental friendly catalysts which support the sustainable treatment technology with the “zero concept” of industrial wastewater. Nevertheless, there is a need to develop more effective methods which consume less energy and are more efficient in pilot scale for the demineralization of pollutant.     

Carbon dioxide sequestration of iron ore mining waste under low-reaction condition of a direct mineral carbonation process

Environmental Science and Pollution Research - Mining waste that is rich in iron-, calcium- and magnesium-bearing minerals can be a potential feedstock for sequestering CO2 by mineral carbonation....     

Sustainable utilization of industrial wastes in controlled low-strength materials: a review

Environmental Science and Pollution Research - The construction industry is experiencing an increasing demand for sustainable alternative materials. There is huge scope for converting the...     

Irrigation model of bleached Kraft mill wastewater through volcanic soil as a pollutants attenuation process

An irrigation process through volcanic soil columns was evaluated for bleached Kraft mill effluent pollutants retention. The system was designed to remove color and phenolic compounds and a simple kinetic model for determining the global mass transfer coefficient and the adsorption rate constant was used. The results clearly indicate that the global mass transfer coefficient values (K(c)a) and the adsorption rate constants are higher for the irrigation processes onto acidified soil. This means that the pretreatment of washing the volcanic soil with an acid solution has a positive effect on the adsorption rate for both pollutant groups. The enhanced adsorption capacity is partially explained by the activation of the metal oxides present in the soil matrix during the acid washing process. Increasing the flow rate from 1.5 to 2.5 ml/min yielded higher (K(c)a) values and adsorption rate constants for both pollutant groups. For instance, regarding color adsorption onto acidified soil, there is an increment of 43% in the (K(c)a) value for the experiment with a flow rate of 2.5 ml/min. Increasing the porosity of the column from 0.55 to 0.59, yielded a decrease in the (K(c)a) values for color and phenolic compounds adsorption processes. Onto natural soil for example, these decreases reached 21% and 24%, respectively. Therefore, the (K(c)a) value is dependent on both the liquid-phase velocity (external resistance) and the soil fraction in the column (internal resistance); making forced convection and diffusion to be the main transport mechanisms involved in the adsorption process. Analyzing the adsorption rate constants (K(c)a)/m, phenolic compounds and color adsorption rates onto acidified soil of 2.25 x 10(-6) and 2.62 x 10(-6) l/mg min were achieved for experiment 1. These adsorption rates are comparable with other adsorption systems and adsorbent materials.     

预处理-水解酸化-厌氧-好氧工艺对玉米淀粉废水有机污染物的降解

采用气相色谱/质谱(GC/MS)、三维荧光光谱(EEM)等检测手段分析预处理/水解酸化/厌氧/好氧组合工艺对玉米淀粉废水有机污染物的降解情况。结果表明,竖流沉淀预处理阶段对TOC平均去除率36.7%,废水中主要为芳烃、烷烯烃以及杂环类物质,EEM产生的5个荧光峰均为芳香蛋白类有机物;水解酸化阶段大部分杂环以及芳烃类有机物水解成有机酸和醇类物质,TOC平均去除率22.7%;厌氧阶段TOC平均去除率最高,达到97.8%,废水中以芳烃和烷烯烃为主,荧光峰减少至2个且强度减弱;好氧阶段TOC平均去除率为61.3%,有机物主要为难降解的长链烷烃物质,芳香蛋白类有机物荧光峰全部消失,新生成了与微生物代谢相关的腐殖酸类物质。     

Use of different organic wastes in reducing the potential leaching of propanil,isoxaben, cadusafos and pencycuron through the soil

In this study, we examined the effect of four different organic wastes (OW)—composted sheep manure (CSM), spent coffee grounds (SCG), composted pine bark (CPB) and coir (CR)—on the potential groundwater pollution of propanil and isoxaben (herbicides), cadusafos (insecticide) and pencycuron (fungicide) under laboratory conditions. For this purpose, leaching studies were conducted using disturbed soil columns filled with a clay loam soil (Hipercalcic calcisol). The addition of organic matter (OM) drastically reduced the movement of the studied pesticides. The results obtained point to the interest in the use of agro-industrial and composted OW in reducing the groundwater pollution by pesticide drainage.     

Retention time profiling of all 136 tetra- through octa- chlorinated dibenzo-p-dioxins and dibenzofurans on a variety of Si-Arylene gas chromatographic stationary phases

The applicability of three different Silphenylene Silicone co-polymer (Si-Arylene) GC stationary phases (J&W Scientific DB-5ms, Varian VF-5ms, and VF-Xms) has been evaluated for the separation of all 136 tetra- through the octa- chlorinated dibenzo-p-dioxins (PCDD) and chlorinated dibenzofurans (PCDF) from closely eluting isomers using gas chromatography/high resolution mass spectrometry (GC/HRMS). Their relative performance data are compared to the “conventional” 5% diphenyl 95% dimethylpolysiloxane GC column (Supelco Equity-5) and to each other based on absolute retention times, visualized mass chromatograms, and the separation of 2,3,7,8-substituted isomers. VF-Xms GC column was able to demonstrate a better performance towards separation of 2,3,7,8-substituted PCDD/PCDF compared to other Si-Arylene GC columns tested, where only 2,3,4,7,8-PnCDF can not be resolved from 1,2,3,6,9-PnCDF and 2,3,4,6,7,8-/1,2,3,6,8,9-HxCDF and 1,2,3,7,8,9-/1,2,3,4,8,9-HxCDF can be at least partially resolved. These data suggest that the development of a single GC column for the separation of all 17 2,3,7,8-substituted dioxins and furans is feasible, which therefore could be used as a standard tool for the PCDD/PCDF methods globally including USEPA methods 1613b, 8290A, 8280B, European Standard Method EN 1948, Canadian methods DFPCB-E3418, EPS 1/RM/19, Japanese methods JIS K0311 and JIS K0312. Having one specific GC column to separate all 2,3,7,8-substituted PCDD/PCDF will significantly improve the data quality, comparability by the various methods and assessment techniques while simultaneously leading to a more cost and time efficient operation.     

两阶段固定化方法制备微囊藻球对Ni2+的去除效果

采用硼酸-硼砂两阶段固定化方法制备PVA-SA复合微囊藻球,综合考察了硼酸(H3BO4)、氯化钙(CaCl2)、硼砂(Na2B4O3·10H2O)、聚乙烯醇(PVA)和海藻酸钠(SA)等因素对藻球性能、固定化过程中PVA泄露及Ni2+去除效果等的影响。结果表明,在以上各因素水平分别为3.5%、2.0%、3.0%、9%和1%时,成球效果、藻球性能较好,固化过程中PVA泄露量较小,Ni2+去除效率较高。两阶段固定化方法可以成功解决PVA-SA包埋固定化技术存在的水溶胀性问题,为其实际运用提供了可能性。     

西南地区某已封场非规范垃圾填埋场垃圾稳定化进程分析

以重庆某非规范填埋场为例,针对西南地区已封场非规范垃圾填埋场的稳定化进程进行了分析。按照场地布局选取4个采样点,在垃圾体上进行钻孔取样,分析不同深度的垃圾样pH值、有机质、含水率、生物可降解度以及垃圾样浸出液和填埋气组成以及各个指标随着填埋深度的变化规律,确定不同深度垃圾体的稳定化程度。结果表明,场内垃圾已呈现矿化垃圾特征;有机质、BDM、浸出液COD以及填埋气CH4含量等4个指标与填埋深度均较好地符合一级降解反应,可以预测垃圾体稳定化临界填埋深度。根据有机质、BDM、浸出液COD以及填埋气CH4含量等4个指标与填埋深度一级降解反应函数预测临界稳定化深度为15 m,与实测值判定的稳定化填埋深度相一致性。在对非规范垃圾填埋场场地利用过程中,需要先对未稳定的上层垃圾进行清理,并在已稳定的底层垃圾体上充填其他稳定介质后利用该地块。     

Dye house wastewater treatment through advanced oxidation process using Cu-exchanged Y zeolite: a heterogeneous catalytic approach

Catalytic wet hydrogen peroxide oxidation of an anionic dye has been explored in this study. Copper(II) complex of NN'-ethylene bis(salicylidene-aminato) (salenH2) has been encapsulated in super cages of zeolite-Y by flexible ligand method. The catalyst has been characterized by Fourier transforms infra red spectroscopy, X-ray powder diffractograms, Thermo-gravimetric and differential thermal analysis and nitrogen adsorption studies. The effects of various parameters such as pH, catalyst and hydrogen peroxide concentration on the oxidation of dye were studied. The results indicate that complete removal of color has been obtained after a period of less than 1h at 60 degrees C, 0.175M H2O2 and 0.3g l(-1) catalyst. More than 95% dye removal has been achieved using this catalyst for commercial effluent. These studies indicate that copper salen complex encapsulated in zeolite framework is a potential heterogeneous catalyst for removal of color from wastewaters.     

一种新型环境矿物材料在废水处理中的应用研究

实验研究表明 ,磷矿石作为一种新型环境矿物材料对重金属离子工业废水具有较好的处理效果 ,且自身具有显著的优点。采用分级处理的方法以及磷矿石的合适用量可以使处理后的工业废水达到排放标准甚至饮用标准 ,同时 ,由于磷矿石去除重金属离子速度快 ,在瞬间即可发生作用 ,使得利用动态法进行工业废水的连续处理成为可能 ,而且不会产生二次污染 ,具有工艺应用意义     

Persistence of chlorpyrifos in a mineral and an organic soil

Chlorpyrifos (Lorsban emulsifiable concentrate) was applied at 3.4 kg AI/ha and incorporated into sand and muck soil contained in small field plots. Soil samples were taken at intervals over 2 yr. Radishes and carrots, seeded yearly, served as indicator crops for absorption of insecticide residues. Samples were extracted and analyzed, by gas-liquid chromatography, for chlorpyrifos, oxychlorpyrifos, and 3,5,6-trichloro-2-pyridinol. Chlorpyrifos residues declined rapidly, with 50% of the initial application remaining after 2 and 8 wk in sand and muck, respectively, and 4 and 9% after 1 yr. Pyridinol residues increased to 13 and 39% of the initial chlorpyrifos application in sand and muck after 1 and 8 wk, respectively, and declined thereafter. Oxychlorpyrifos was detected in the 2 soils at very low levels only in immediate posttreatment samples. In the first year of the study low levels (less than 0.1 ppm) of chlorpyrifos and the pyridinol were detected in radishes and carrots.