Content, mobility and transfer behavior of heavy metals in MSWI bottom ash in Zhejiang province, China

Municipal solid waste incinerator (MSWI) bottom ash samples were taken from six cities of Zhejiang province, where 1/4 incinerators of China were located. The samples were instrumentally analyzed to detect the content of heavy metals. Sequential extraction procedure (SEP) was adopted to characterize the mobility and environmental impact of heavy metals. And the transfer coefficients of heavy metals from the input MSW to the bottom ash during the incineration were also calculated. It showed that the average content of Zn, Mn, Cu, Pb and Cr in the bottom ash exceeded 300 mg/kg, which was much higher than that in the soils. SEP results showed that although the residue fraction was the primary fraction of the heavy metals in the bottom ash, there were still 1.84 mg of Cd, 86.21 mg of Cu, 83.46 mg of Pb and 939.46 mg of Zn in 1 kg bottom ash having the potential of leaching, which indicated a great threat to the surrounding environment. The result of coefficients calculation revealed that almost all the Cu, Cr, Mn and Ni in the input MSW were transferred to the bottom ash during the incineration. Bottom ash was also the main destination of Cd, Co, As, Mo, Pb and Zn though considerable amounts of those metals were transferred to the raw gas.     

废弃混凝土中基质胶凝组分作原料煅烧水泥熟料的研究

每年拆除建筑物所产生的废弃混凝土数量巨大,因此废弃混凝土中基质胶凝组分作原料煅烧水泥熟料的再利用研究具有重要的意义。采用热处理和加入表面活性剂与机械粉碎相结合的方法将废弃混凝土中的骨料与基质胶凝组分进行了分离。将分离出的基质胶凝组分按不同配合比制备生料,分别在1400℃,1450℃下进行了熟料煅烧试验,并进行了结构和力学性能测定。试验结果表明,水泥净浆试体的抗压强度随基质胶凝组分配合比的增大而降低,但适当掺入(小于25%)时降低幅度不大;XRD和SEM分析结果表明,1450℃煅烧的熟料矿物结构与常规原料煅烧的熟料基本相同。根据晶种理论和水化物脱水相的反应活性分析了熟料烧成机理。     

High intakes of Cr, Ni, and Zn in clinker: Part I. Influence on burning process and formation of phases

The influence of high intakes of Cr, Ni, and Zn on the burning process and the formation of clinker phases is described. Three different raw meals were used and were burned with the metal oxides in four concentrations from 200 to 25,000 ppm. The resulting clinker was analysed for the content of free lime and X-ray diffraction analysis was done. Some of the clinker material was crushed and polished, and quantitative point counting was performed to provide the content of the different clinker phases. These samples were also analysed by scanning electron microscope connected with an energy-dispersive X-ray-spectrometer to detect the composition of the clinker phase. The results show that only very high intakes of heavy metals have measurable effects on the formation and composition of the clinker.     

原料预均化及其在优质矾土生产中的应用

原料预均化的基本原理为“平铺直取”．标准偏差和均化效果是考核均化过程的两个重要指标。标准偏差越小表示物料成分越均匀。原料预均化方式有多种，料仓式原料预均化库综合了各种方式的优点，它具有投资少，密封性好，占地面积小，无粉尘，操作条件和均化效果好等特点。     

Extraction of anthocyanins and luteolin from Arrabidaea chica by sequential extraction in fixed bed using supercritical CO2, ethanol and water as solvents

Phenolic compounds from Arrabidaea chica Verlot leaves, besides conferring staining properties to their extracts, also have various biological activities including anti-inflammatory and wound-healing properties. To evaluate new possibilities for obtaining extracts with differentiated yield and composition, sequential extractions in fixed bed were performed at 40 and 50 °C, and 300 and 400 bar, using as extracting solvents pure supercritical carbon dioxide (scCO₂) in a first step, acidified ethanol in a second step and acidified water in a third extraction step. Four flavonoids of interest were investigated in the extracts, one of them being flavone (luteolin), and three anthocyanin compounds of type 3-desoxyanthocyanidins which were quantified by high performance liquid chromatography (HPLC). The extraction curves, the global yields and the concentration and yield of the compounds under study were evaluated. The results indicated that the cumulative total yields in the three steps ranged from 22% to 27% in all conditions of temperature and pressure, with the highest global yield at 50 °C and 300 bar. Although the lowest extraction yield was obtained using pure scCO₂, this step was highly selective, since only carajurin in its aglycone form was extracted among the compounds of interest and this was confirmed by analysis of MS/MS.     

Extraction of phenolic compounds from pitanga (Eugenia uniflora L.) leaves by sequential extraction in fixed bed extractor using supercritical CO2, ethanol and water as solvents

With the goal of maximizing the extraction yield of phenolic compounds from pitanga leaves (Eugenia uniflora L.), a sequential extraction in fixed bed was carried out in three steps at 60 °C and 400 bar, using supercritical CO₂ (non-polar) as solvent in a first step, followed by ethanol (polarity: 5.2) and water (polarity: 9.0) in a second and third steps, respectively. All extracts were evaluated for global extraction yield, concentration and yield of both polyphenols and total flavonoids and antioxidant activity by DPPH method (in terms of EC₅₀). The nature of the solvent significantly influenced the process, since the extraction yield increased with solvent polarity. The aqueous extracts presented higher global extraction yield (22%), followed by ethanolic (16%) and supercritical extracts (5%). The study pointed out that the sequential extraction process is the most effective in terms of global extraction yield and yield of polyphenols and total flavonoids, because it produced the more concentrated extracts on phenolic compounds, since the supercritical ethanolic extract presented the highest phenolics content (240.5 mg GAE/g extract) and antioxidant capacity (EC₅₀ = 9.15 μg/mL). The most volatile fraction from the supercritical extract, which is similar to the essential oils obtained by steam distillation or hydrodistillation, presented as major compounds the germacrenos D and B + bicyclogermacrene (40.75%), selina-1,3,7(11)-trien-8-one + selina-1,3,7(11)-trien-8-one epoxide (27.7%) and trans-caryophyllene (14.18%).     

Study of the potential valorisation of heavy metal contaminated biomass via phytoremediation by fast pyrolysis: Part I. Influence of temperature, biomass species and solid heat carrier on the behaviour of heavy metals

Presently, little or no information of implementing fast pyrolysis for looking into the potential valorisation of heavy metal contaminated biomass is available. Fast pyrolysis of heavy metal contaminated biomass (birch and sunflower), containing high amounts of Cd, Cu, Pb and Zn, resulting from phytoremediation, is investigated. The effect of the pyrolysis temperature (623, 673, 773 and 873 K) and the type of solid heat carrier (sand and fumed silica) on the distribution of the heavy metals in birch and sunflower pyrolysis fractions are studied. The goal of the set-up is “concentrating” heavy metals in the ash/char fraction after thermal treatment, preventing them to be released in the condensable and/or volatile fractions. The knowledge of the behaviour of heavy metals affects directly future applications and valorisation of the pyrolysis products and thus contaminated biomass. They are indispensable for making and selecting the proper thermal conditions for their maximum recovery. In view of the future valorisation of these biomasses, the amounts of the pyrolysis fractions and the calorific values of the obtained liquid pyrolysis products, as a function of the pyrolysis temperature, are determined.     

High intakes of Cr, Ni, and Zn in clinker: Part II. Influence on the hydration properties

This work presents the results of the hydration of cements with high intakes of Cr, Ni, and Zn. The cements were produced from clinkers that were doped with 200 to 25,000 ppm of heavy metal. Investigations on the clinkers were presented in Part I. In this paper the rate of heat generation of the cements in the first 2 days was analysed by differential scanning calorimetry. The hydration products were investigated by scanning electron microscopy combined with energy-dispersive X-ray spectrometer and also by X-ray powder diffraction. The initial setting of some samples was tested, as well as the strength. The results show that heavy metals only have an influence on the hydration properties of the cements if the dosage is much higher than in ordinary Portland cement.     

Study of the leaching behaviour of paving concretes: quantification of heavy metal content in leachates issued from tank test using demineralized water

The leaching behaviour of concretes made from porphyry aggregate, river sand and Portland cement or blast furnace slag cement has been studied by means of a tank test using demineralized water in accordance with NEN 7345. The results show that the amount of heavy metals leached is small, much lower than the parametric values specified by the European Directive defining the quality of drinking water, and becomes negligible after prolonged immersion.At the end of the tank test, the fraction of heavy metals leached by the concrete represents less than 1% of the total heavy metal content of the cement. To refer to the bulk content as a criterion of environmental quality is therefore unjustified and unduly restrictive.The results suggest that the controlled use of alternative fuels and raw materials to replace natural materials does not in any way alter the leaching behaviour. Similarly, the replacement of a defined fraction of the clinker with blast furnace slag does not compromise the environmental compatibility of the concrete in terms of the heavy metals it releases.A second finding of these experiments is that the risk of contamination due to release of heavy metals from concrete on-site appears small. The total heavy metal content of concrete is of the same order of magnitude as (or even smaller than) that of a soil considered as being unpolluted in Belgium. Moreover, the fraction of heavy metals released by the concrete as a proportion of this total heavy metal content is nonsignificant.     

Influence of treated sewage sludge applications on temporal variations of plant nutrients and heavy metals in a Typic Xerofluvent soil

The objective of this study is to determine influence of Treated Sewage Sludge (TSS) rates as organic matter and nutrient resource on temporal variations of some macronutrients and micronutrients and heavy metals concentrations in a Typic Xerofluvent soil. The experiment was conducted in Menemen Plain, in the Western Anatolia Region of Turkey in 2003–2005. Moist TSS was added to the soil at the rates of 0, 30, 60 and 90 Mg ha⁻¹ on May 1, 2003. Peanut (Arachis hypogaea) was planted as the first crop. On the other hand, mixture of green barley (Hordeum vulgare) and common vetch (Vicia sativa L.) was planted as the second crop. During the experiment, soil samples were taken five times. Increasing TSS applications to this soil resulted in significantly increased concentrations of total N, Cu, Pb and Ni, and available P, K, Ca, Fe, Cu, Zn, Mn concentrations in soil. However, concentrations of available Mg and Na, total Fe, Zn, Mn, Cd, Co and Cr in soil did not significantly change. Micronutrients and heavy metals concentrations in soil were found under threshold values in all sampling periods in this study. Available nutrient concentrations in the soil decreased particularly in the last sampling periods because of plant uptake of nutrients from the applied TSS. It is recommended that 90 Mg ha⁻¹ moist TSS can be added once in a 2-year period for improving nutrient concentrations in Typic Xerofluvent soil.     

Separation and recovery of heavy metals from concentrated smelting wastewater by synergistic solvent extraction using a mixture of 2-hydroxy-5-nonylacetophenone oxime and bis(2,4,4-trimethylpentyl) -phosphinic acid

Extraction and separation of copper, zinc, nickel, and cadmium from calcium and magnesium in concentrated smelting wastewater by synergistic solvent extraction using a mixture of 2-hydroxy-5-nonylacetophenone oxime (Mextral 84H) and bis(2,4,4 -trimethylpentyl)-phosphinic acid (Cyanex 272) in an aliphatic diluent (DT-100) was studied. The effects of extractant concentrations, equilibrium pH, organic-to-aqueous phase ratios, system temperature, and extraction and stripping efficiencies on the extraction performance of the heavy metals were investigated. Extraction of pH isotherms showed that addition of Cyanex 272 to Mextral 84H causes obvious synergistic shifts for zinc and cadmium and a slightly antagonistic shift for nickel. The separation factor of cadmium over magnesium was 155.7 and the ΔpH₅₀ values between the metals were over 1.00 pH units. Semi-continuous tests for the metals extraction, scrubbing, and stripping were conducted in a continuous extraction apparatus with conditions further optimized for separation of the metals. Nearly 100% of the copper and nickel and over 98% of the zinc and cadmium were recovered with less than 0.1 mg/L copper and nickel, 26 mg/L of zinc, and 10 mg/L of cadmium remaining in the raffinate. A process in which all valuable metals are extracted simultaneously and stripped selectively at optimal conditions is proposed that is entirely feasible for the separation of copper, zinc, nickel, and cadmium from calcium and magnesium in concentrated smelting wastewater. The study determines the fundamental parameters for the treatment of smelting wastewater by solvent extraction.     

Critical evaluation of sequential extraction and sink-float methods used for the determination of Ga and Ge affinity in lignite

The affinities of Ga and Ge in lignite were determined using sequential extraction (SE) and element affinity calculation (EAC) based on sink-float data. For this study a bulk lignite sample was fractioned into two sets. The first set of samples (A) consisted of the different grain sizes fractions; the second one set (B) was prepared by density fractionation. Sequential extractions [1] were performed on both sets of fractions with very good agreement between determined organic elements affinities (OEA of Ga evaluated from A data is 32%, from B data 35%; OEA of Ge evaluated from A data is 31% and from B data 26%). The data of B lignite fractions were evaluated using two element affinity calculations: (a) EAC (I) of Klika and Kolomazník [2] and b) newly prepared subroutine EAC (II) based on quantitative contents of lignite macerals and minerals. There was also good agreement between both methods obtained (OEA of Ga calculated by EAC (I) is 83% and by EAC (II) 77%; OEA of Ge calculated by EAC (I) is 89% and by EAC (II) 97%). The significant differences of organic elements affinities of Ga and Ge evaluated by sequential extraction and by element affinity calculation based on sink-float data are discussed.     

Flame atomic absorption spectrometric determination of Cd,Pb, and Cu in food samples after pre-concentration using 4-(2-thiazolylazo) resorcinol-modified activated carbon

This work aimed to develop a solid-phase extraction method using low-cost activated carbon produced from waste and modified with 4-(2-thiazolylazo) resorcinol for Cd(II), Pb(II), and Cu(II). The results showed that quantitative recovery of analytes was obtained at pH 6 with 3 M nitric acid as the eluent and a sample volume up to 1000 mL. The method was validated using certified reference material and addition-recovery tests. The limits of detection (LODs) for Pb(II), Cd(II), and Cu(II) were 2.03 μg L⁻¹, 0.15 μg L⁻¹, and 0.19 μg L⁻¹, respectively. The procedure was applied for determination of analytes in food samples.     

Synergistic effects in the solvent extraction of some divalent metals by mixtures of versatic 10 acid and pyridinecarboxylate esters

Pyridinecarboxylate esters were found to cause appreciable synergistic shifts in the pH₅₀ values for the extraction of some divalent base metals by solutions of Versatic 10 acid in xylene. For n-octyl 3-pyridinecarboxylate, the synergistic shifts decreased in the order Ni > Co > Cd > Cu ≈ Fe > Mn > Zn, and for the commercial extractant Acorga DS5443A in the order Ni > Cu > Co > Fe > Cd > Mn > Zn. No synergistic effects were observed for divalent lead, calcium and magnesium. On the basis of the pH₅₀ values obtained, several possible practical metal separations are suggested. No loss of metal-loading capacity was found when the organic phases were contacted with 1 M sulphuric acid for prolonged periods at 30°C. The effect of changes in the structure of a series of isomeric octyl pyridinecarboxylates is reported for one of the smaller cations studied (copper), as well as for one of the larger cations (cadmium).     

The adsorption of PAHs, BTEX, and heavy metals on surfactant-modified desulfurization sorbents in a dry scrubber

The injection of dry Ca-based sorbents for removing acid gases had been investigated previously. However, the utilization of Ca-based sorbents for adsorbing other air pollutants was rarely examined. The objective of this study was to investigate the reduction of organic compounds polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylene (BTEX) and heavy metals by using the desulfurization sorbents in a dry scrubber integrated with a fabric filter. Four surfactants, calcium lignosulfonate, sodium lignosulfonate, alkyl naphthalene sodium sulfonate and β-naphthalene sodium sulfonate condensates, were used as additives to modify the surface characteristics of desulfurization sorbent calcium hydroxide (Ca(OH)₂). Modifying the desulfurization sorbents with surfactants showed different effects on removal of PAHs, BTEX, and heavy metals, and exploited the potential of Ca-based sorbents for adsorbing air pollutants other than SO₂.     

污泥重金属提取剂浸提效率及经济性比较

污泥中重金属的潜在危害严重影响其处理处置效果,因此本文研究了各种提取剂对污泥重金属的浸提效果,并依据经济可提取指数与浸提效果进行了经济性分析。结果表明,无机酸提取剂对污泥重金属的浸提效果随其pH值升高而降低,H⁺浓度是影响其浸提率的主要因素。低分子量有机酸提取剂对污泥中重金属的浸提效率随其浓度增加而增大,其对3种重金属的提取效率顺序为Zn> Cr> Cu。Zn是最易被提取的重金属,草酸对污泥重金属的浸提效果优于柠檬酸。污泥重金属浸提率与高分子量有机酸提取剂浓度呈正相关,其对3种重金属的提取效率顺序为Zn> Cu> Cr。污泥重金属的浸提一般应优先选用有机酸提取剂,对污泥重金属Zn的提取宜选用柠檬酸和草酸,对污泥重金属Cr和Cu的提取一般应选用柠檬酸和乙二胺四乙酸。     

The activity of Rh/Al2O3 and Rh-Na/Al2O3 catalysts for PAHs removal in the waste incineration processes: Effects of particulates, heavy metals, and acid gases

This study investigated the activity of Rh/Al₂O₃ and Rh-Na/Al₂O₃ catalysts for polycyclic aromatic hydrocarbons (PAHs) removal and the influence of particulates, heavy metals, and acid gases (SO₂ and HCl) on the performance of catalysts. The experiments were carried out in a laboratory-scale waste incineration system. Experimental results show that the destruction removal efficiency (DRE) of PAHs by Rh/Al₂O₃ and Rh-Na/Al₂O₃ catalysts were 80% and 59%, respectively when the flue gas did not contain any pollutants. The concentrations of PAHs increased by using a Rh/Al₂O₃ catalyst when the flue gas contained Cd, Pb, and SO₂ and also increased by using a Rh-Na/Al₂O₃ catalyst when the flue gas contained particulates, Cd, and HCl. Adding Na to the Rh/Al₂O₃ catalyst can inhibit the increases of 3-4 ring PAHs when the flue gas contained Pb. The influence of acid gases on the performance of the Rh/Al₂O₃ and Rh-Na/Al₂O₃ catalysts followed the sequence SO₂ > HCl > SO₂ + HCl. The activity of the catalysts for PAHs removal was significantly suppressed by increased concentrations in particulates and Cd, yet promoted by a high Pb concentration. The results of ESCA analysis indicated that the presence of Cd and Pb did not change the chemical states of Rh and Na, but the presence of SO₂ and HCl did.     

Sulfate removal from aqueous solutions by hydrous iron oxide in the presence of heavy metals and competitive anions : Macroscopic and spectroscopic analyses

Sulfate removal from aqueous solutions by hydrous iron oxide freshly prepared in the presence of some heavy metals cations and some anions has been investigated in batch systems by varying the pH and concentrations of various ions. Infrared spectroscopic analyses have been performed to characterize the effect of these ions on the mechanism of sulfate interaction with the surface of the hydrous oxide.The results of macroscopic studies show that in the binary systems, copper and zinc ions inhibit the sulfate removal at pH higher than 5.5. In the presence of oxalate and phosphate ions, significant competitive effects are observed contrary to acetate ions.The IR spectra of the solids obtained show that among the studied ions, only phosphate ions have an effect on the sulfate interaction with the surface of the oxide. In their presence, the formation of outer sphere complex is more probable.     

Biosorbents based on pine sawdust and malt sprouts for preconcentration and ICP-OES determination of nonferrous,heavy, and precious metals in the environmental samples

Pine sawdust and malt sprouts modified with orthophosphoric acid and carbamide have been proposed for solid-phase extraction (SPE) of nonferrous, heavy, and precious metals and their subsequent determination in the environmental samples by inductively coupled plasma optical emission spectrometry (ICP-OES). Modified adsorbents were characterized by SEM, TGA, and FT-IR and compared with native matrixes. SPE of some nonferrous and precious metal ions by biosorbents was studied. Depending on the SPE conditions, it was possible to separate nonferrous and heavy metals from alkali and alkaline earth metals. The proposed adsorbents are effective for preconcentration of nonferrous and heavy metals from natural waters and precious metals from solutions after digestion of geological samples.     

Damage evolution analysis in mortar, during compressive loading using acoustic emission and X-ray tomography: Effects of the sand/cement ratio

This paper explores the use of acoustic emission (AE) and X-ray tomography to identify the mechanisms of damage and the fracture process during compressive loading on concrete specimens. Three-dimensional (3D) X-ray tomography image analysis was used to observe defects of virgin mortar specimen under different compressive loads. Cumulative AE events were used to evaluate damage process in real time according to the sand/cement ratio. This work shows that AE and X-ray tomography are complementary nondestructive methods to measure, characterise and locate damage sites in mortar. The effect of the sand proportion on damage and fracture behaviour is studied, in relation with the microstructure of the material.