Thermal Treatment for Incinerator Ash: Evaporation and Leaching Rates of Metals

The disposal of different residues containing high concentrations of heavy metals causes environmental problems. To understand the effects of various properties of the residues on the evaporation and leaching rates of heavy metals (Cd, Pb, Zn, Cr, and Cu) by thermal treatment, three types of residues (including bottom ash, spray dryer ash, and baghouse ash) generated from various incineration conditions including spray dryer additives (SiO2, CaCl2, and NaHCO3), and feedstock additives [polyvinyl chloride (PVC), and NaCl] were investigated in the present study. The results indicated that the evaporation rate of Cd and Pb in the spray dryer ash and in the baghouse ash was higher than that in the bottom ash. The leaching rate of heavy metals in the spray dryer ash was less than 20% before the thermal treatment when Ca(OH)2 was used in the spray dryer. The addition of PVC could increase the evaporation rate of Zn in the spray dryer ash, whereas the addition of NaCl could decrease the leaching rate of Zn and Cu in the baghouse ash after the thermal treatment.     

Size Distribution of Heavy Metal Aerosols in Cooling and Spray Dryer System

The cooling process prior to treating flue gas and the spray dryer process that removes acid components in flue gas are believed to influence the mass and elemental size distributions of heavy metal in fly ash. The main objective of this study was to investigate the effects of operating parameters on the mass and elemental size distributions of heavy metals in fly ash produced from a fluidized bed incineration and a water cooling or spray dryer flue gas treatment system. The operating parameters investigated included (1) the controlling temperature in the gas cooling system; (2) the controlling temperature in the spray dryer system; (3) the addition of organic chloride; and (4) the addition of inorganic chloride. The experimental results indicated that the water cooling process and spray dryer process increase the amount of coarse fly ash (5–125 μm) and increase the total concentration of metal in fly ash. The amounts of fine fly ash (0.1–15.72 μm) and the total concentration of metal in fine fly ash increase with decreasing temperature during the water cooling process. However, the amounts of fine fly ash (0.1–15.72 μm) and the total concentration of metal in fine fly ash decrease with decreasing temperature during the spray dryer process.     

Dynamic Adsorption of Heavy Metals under Various Incineration Temperatures

Previous studies have indicated that an effective control technology, for heavy metal emissions from incinerators, is to use solid sorbents to capture metals by physical deposition and chemical adsorption. The controlling efficiency is affected by the kind and size of sorbents, the operating temperature, and the specific compositions of the waste. However, the dynamic adsorption behavior of heavy metals on sorbents during incineration is rarely discussed, because it is difficult to analyze and identify trace metals at high temperatures. The main objective of this study is to investigate the dynamic adsorption behavior of Cr, Cu, Pb, and Cd on sorbents (silica sand with limestone) at different operating temperatures (600, 700, and 800°C) and to find the adsorption saturation point of the sorbents during fluidized bed incineration. This will help us to determine when the sorbents should be renewed and investigate the adsorption mechanism. The results show that the adsorption saturation points of three of the four metals were: (1) Cr, 1.4 mg∕g at 600°C, 1.04 mg∕g at 800°C; (2) Pb, 16.08 mg∕g at 600°C, 12 mg∕g at 800°C; and (3) Cu, 10.6 mg∕g at 600°C, 5.34 mg∕g at 700°C. The adsorption capacity follows the sequence of Pb > Cu > Cr > Cd.     

新型缓释EDTA对土壤铅镉释放的影响

利用羧甲基壳聚糖的环境友好性和成模性将其作为缓释载体,将EDTA和羧甲基壳聚糖按照1∶1的配比通过喷雾干燥器制备了的缓释EDTA。以缓释EDTA为研究对象,进行了表征分析、缓释动力学研究、土壤重金属静态活化特性和动态淋溶特性研究。结果表明,缓释EDTA包封率可达87.51%,在水中释放过程符合Higuchi模型,具有明显的缓释效果。缓释EDTA相比EDTA可以在提高土壤溶液中Pb、Cd离子浓度的同时有效控制Pb、Cd离子的突增,促使土壤溶液中的Pb、Cd离子保持适量浓度持续提升。动态淋溶结果表明,添加两种不同形式的EDTA会显著提升Pb、Cd的淋失量,但缓释EDTA处理能显著降低Pb、Cd的初始淋失量和淋失总量,其中Pb和Cd的淋失总量分别降低了19.5%和20.9%。     

火焰原子吸收光谱法在分析污泥焚烧飞灰中重金属化学形态上的应用

应用微波消解-火焰原子吸收光谱法(FAAS)测定污泥焚烧飞灰中的Cd、Cr、Cu、Mn、Ni、Pb、Zn等各重金属元素总量。研究发现,样品用HNO3-HF混合酸经微波消解后, 溶解时间由原来的3～5 h缩短到30 min。选择合适的分析谱线, 用FAAS直接测定试液中上述7种重金属元素各自总量及其不同形态含量,所得各元素的线性相关系数均大于0.999 0。分析结果表明,污泥焚烧飞灰中重金属Zn, Pb, Mn含量较高, 而Ni的含量较低; 污泥焚烧飞灰中含有的重金属除Cr相对比较稳定外, 其它重金属元素的不稳定态所占比例均很高。 处置污泥焚烧飞灰时应选择不同的处置和利用方式,尽可能地将污泥焚烧飞灰中重金属的化学形态由不稳定态转变为稳定态。     

赣江上游龙迳河水体氨氮与重金属污染分布特征及风险评价

论文以我国典型的稀土矿区流域——赣江上游龙迳河为研究对象,自上游至下游采集了15个水样并现场测定了水体pH值,测试和分析了氨氮、硝氮、亚硝氮和Cr、Cd、Zn、Cu、As、Hg、Pb、Mn 8种重金属含量和相关性,并采用内梅罗综合污染指数评价法对重金属污染程度进行评价.结果表明:①龙迳河流域主要的重金属污染物为Mn、Hg、Pb,其超出地表Ⅱ类水质标准分别为93%、20%、6.7%;②表层水体中亚硝氮、硝氮、氨氮和重金属Zn、Mn、As、Cd、Pb沿程变化具有相似性,且重金属Zn、Mn、As、Cd、Pb与氨氮具有显著的正相关性,表明重金属Zn、Mn、As、Cd、Pb之间可能具有一定的同源性且氨氮含量与该重金属在水中的分布有密切联系;③龙迳河水质优良、良好、较好、较差和极差占整体采样点的概率分别为6.67%、26.67%、33.33%、6.67%和26.67%,河流水质整体较差,部分采样点水质较好,重金属污染上游大于下游.      

赣州市土壤重金属形态分布特征及污染评价

以赣州市6大功能区土壤重金属为研究对象,采取表层0~20cm土壤共50个样品,测定土壤中重金属Pb、Zn、Cu、Cd和Cr含量并分析其来源,采用改进BCR连续提取法进行形态分析,结合次生相与原生相分布比值法、单因子指数法进行污染评价。结果表明研究区土壤中Pb和Cu元素变异系数较大,重金属Zn, Cu和Pb之间相关性显著。通过单因子指数法评价结果可以看出,赣州市6大功能区都受到重金属Cd的重度污染,居民区和工业区受到重金属Cr的轻度污染,交通区受到重金属Pb和Zn的轻度污染。研究区土壤重金属Cd、Cr、Cu、Pb、Zn形态都以残渣态为主,次生相与原生相比值都是小于1的属于无污染。      

Carbonation of Municipal Solid Waste Incineration Fly Ash and the Impact on Metal Mobility

Fly ash from municipal solid waste incineration (MSWI) is considered as hazardous waste that calls for a robust, reliable, and reasonable treatment technique. This investigation aims to assess the impact of CO2 partial pressure, water addition, time, and temperature on the stabilization of MSWI fly ash with particular emphasis on Pb, Zn, Cd, and Cr. Carbonation and element mobility were studied by applying thermal analysis and leaching assays on fly ash samples treated according to a 24 factorial design. The relationship between the factors and the response variables was evaluated using partial least squares modeling. Chemical equilibrium calculations were performed so as to complement the experimental findings. Decalcification of carbonated fly ash in a typical Swedish landfill was estimated at 0.13?mm?yr?1 Treatment through carbonation reduced the availability of Pb and Zn about 100 times and also the carbonate alkalinity of 7.4?eq?(kg?FS)?1 (FS represents the fixed solids) was remedied successfully. However, shortcomings that need to be resolved are the remobilization of Cr with time and the mobilization of Cd.     

某锰矿区土壤剖面重金属形态迁移转化特征及生态风险评价

对贵州省某锰矿区剖面土壤进行采样,测定其中Cu、Zn、Cr、Mn、Pb和Cd含量,并采用改进的BCR连续提取法分析重金属的赋存形态,利用风险评价编码法（RAC）及次生相与原生相比值法（RSP）对其进行风险评价。结果表明,1）研究区域土壤中Cd、Cr、Cu、Zn、Pb和Mn的质量浓度平均值分别为2.63、126.39、48.95、751.8、37.28和4 992.88 mg/kg,均高于贵州土壤背景值。从土壤重金属垂向分布来看,由于矿区土壤受到较多人为影响,导致土壤垂向重金属元素含量未表现出明显的规律性。2）不同重金属的赋存形态分布差异较大,Cd的主要赋存形态为弱酸溶态,Pb、Mn均以可还原态为主,Cr、Zn和Cu均以残渣态为主,其中Cd、Cu元素有效态均表现出在表层富集的特征。3）潜在生态风险评价结果表明,研究区域土壤Cd有较高的污染风险,土壤Cu、Mn、Zn、Pb和Cr以中低风险为主。不同剖面深度土壤Cd和Cu生物有效形态组分污染风险均呈由浅至深逐渐降低的趋势。     

Adsorption on Carbon and Zeolite of Pollutants from Flue Gas during Incineration

The volatile organic compound, polycyclic aromatic hydrocarbon, dioxin, and metallic components released from incineration threaten human health. These pollutants, appearing in a molecular state, cannot be effectively removed by baghouse and electrostatic precipitators through capture and filtration mechanisms. Previous studies indicate that activated carbon is conventionally used to remove organic compounds from gas at low temperatures (less than 30°C). However, the adsorption characteristics of organic compounds from a gas phase at high temperatures (over 120°C) are seldom mentioned. Moreover, the complex compositions of flue gas cause the adsorption characteristics of organic compounds and heavy metals on adsorbent tubes to be more complicated. This research examines the adsorption characteristics of organic compounds and heavy metals at various incineration conditions. The evaluated parameters include: (1) the operating temperatures; (2) the characteristics of adsorbents (activated carbon and zeolite); and (3) waste compositions and the presence of heavy metals. The results indicate that activated carbon has a high adsorption capacity compared with zeolite.     

典型锰矿区周边农田土壤重金属污染风险评价及其来源分析

为探究典型锰矿区周边农田土壤重金属污染状况及主要来源,以重庆市秀山县溶溪锰矿区周边农用地的土壤为研究对象,测定了土壤中镉、砷、铅、铬、镍、铜、锌和锰的含量,采用了多种分析方法（包括多元统计分析、单因子污染指数法、内梅罗指数法和地质累积指数法）研究土壤重金属污染水平、分布特征,并结合皮尔逊相关性分析、PCA和APCS-MLR分析,解析研究区土壤重金属的主要来源和贡献率。结果表明,锰矿区周边水稻田土壤Mn均值含量显著低于其它农作物土壤（p＜0.05）,其他7种重金属均值含量在各农田土壤中均无显著差异（p＞0.05）。内梅罗综合污染指数表现为红薯地（13.34）＞大豆地（2.73）＞玉米地（2.19）＞水稻田（1.80）,重金属污染程度由大到小表现为：Mn＞Cd＞As＞Ni、Zn＞Pb、Cr、Cu。地累积指数由大到小表现为：Mn＞As＞Pb＞Zn＞Ni＞Cd＞Cu＞Cr。污染源解析表明,研究区土壤中Cd、Pb、Ni、Cu、Zn和Mn之间存在显著正相关关系（r=0.5~0.8、p＜0.01）,主要受到矿业开采等活动影响,贡献率分别为80.0%、55.3%、57.9%、61.4%、73.3%和98.4%。As和Cr存在显著正相关关系（r=0.548、p＜0.01）,主要受到土壤母质等自然因素的影响,贡献率分别高达88.5%和76.3%。因此,应重点加强对Mn和Cd的来源管控和污染防治。此外,红薯地8种重金属污染累积程度均高于其他农作物土地,应开展相应整治,防止持续对红薯地土壤造成污染。     

Structures and Metal Leachability of Sintered Sludge-Clay Ceramsite Affected by Raw Material Basicity

To solve the disposal problem of wastewater treatment sludge (WWTS), WWTS was mixed with clay and water glass (sodium silicate) for the production of lightweight ceramsite. The effect of mass ratio of CaO/SiO2 (defined as basicity) on physicochemical characteristics of ceramsite and stabilization of heavy metals was investigated. It was found that the optimal basicity for making ceramsite ranges was 0.024–0.069. The main thermal changes ( ≤ 1,000??°C) are phase transformations, which are caused by the evaporation and volatilization of water and carbonous matters and, finally, by the oxidation and decomposition of inorganic matters and minerals. Anorthite [Ca(Al2Si2O8)] and amorphous silica (SiO2) increase as the basicity increases. The formation of more multiple crystalline phases is the main reason for the decrease in the compressive strength of the ceramsite with higher basicity. Leaching contents of Cd, Cu, Cr, and Pb decrease as the basicity increases. The stable compounds of heavy metals in ceramsite are PbCrO4, Cr2O3, CdSiO3, and CuO, which prove that strong chemical bonds are formed and the leachability of these heavy metals is greatly reduced by the crystallization and chemical incorporation process. Results indicate that basicity can be used as an important parameter for controlling the properties of ceramsite.     

高炉喷吹垃圾焚烧飞灰预处理工艺分析

为了解决高炉协同处置垃圾焚烧飞灰时氯负荷高的问题,以去离子水作为洗脱剂,通过考查不同水洗条件(水灰比、水洗时间、水洗温度、水洗次数)下垃圾焚烧飞灰中Cl元素和重金属元素的脱除效果,对飞灰高炉焚烧固化预处理中的工艺参数进行研究。结果表明,飞灰中Cl主要以NaCl、KCl、CaClOH的形式存在。在高炉协同处理前水洗预处理的适宜条件为水灰比为4 ml/g、水洗时间为5 min、水洗温度为25℃、水洗1次。在此条件下飞灰中Cl脱除率为86.45%、Zn脱除率为4.77%、Pb脱除率为35.65%、Cu脱除率为7.63%、Cr脱除率为9.71%。水洗后飞灰的配加比例、单位时间喷吹量、喷吹速度需按企业自身情况确定。在高炉喷煤比为139.12 kg/t(Fe)和飞灰喷吹量为喷煤量的1%条件下,由水洗后飞灰带入高炉的Cl质量为0.078 kg/t(Fe)、Zn为9.74×10^-3 kg/t(Fe)、Pb为1.53×10^-3 kg/t(Fe)、Cu为8.35×10^-4 kg/t(Fe)、Cr为9.88×10^-5 k...     

高炉喷吹垃圾焚烧飞灰预处理工艺分析

为了解决高炉协同处置垃圾焚烧飞灰时氯负荷高的问题,以去离子水作为洗脱剂,通过考查不同水洗条件(水灰比、水洗时间、水洗温度、水洗次数)下垃圾焚烧飞灰中Cl元素和重金属元素的脱除效果,对飞灰高炉焚烧固化预处理中的工艺参数进行研究。结果表明,飞灰中Cl主要以NaCl、KCl、CaClOH的形式存在。在高炉协同处理前水洗预处理的适宜条件为水灰比为4 ml/g、水洗时间为5 min、水洗温度为25 ℃、水洗1次。在此条件下飞灰中Cl脱除率为86.45%、Zn脱除率为4.77%、Pb脱除率为35.65%、Cu脱除率为7.63%、Cr脱除率为9.71%。水洗后飞灰的配加比例、单位时间喷吹量、喷吹速度需按企业自身情况确定。在高炉喷煤比为139.12 kg/t(Fe)和飞灰喷吹量为喷煤量的1%条件下,由水洗后飞灰带入高炉的Cl质量为0.078 kg/t(Fe)、Zn为9.74×10-3 kg/t(Fe)、Pb为1.53×10-3 kg/t(Fe)、Cu为8.35×10-4 kg/t(Fe)、Cr为9.88×10-5 kg/t(Fe),远低于一般高炉熔炼要求,可以满足高炉正常运行需求。     

某铅锌尾矿库周边土壤重金属污染特征及其来源分析

以某铅锌尾矿库周边土壤为研究对象,测定土壤中Cd、Hg、As、Pb、Cr、Cu、Zn、Ni重金属含量,采用地质统计分析掌握重金属含量空间分布,再利用单因子污染指数、内梅罗综合污染指数和地质累积指数评价重金属污染状况,并结合相关性分析和主成分分析探重金属来源。结果表明,土壤中Cd、Hg、As、Pb、Cr、Cu、Zn、Ni平均含量分别为10.4、1.54、132、653、62.8、73.8、1 392、31.6 mg/kg,越靠近尾矿库,Cd、As、Pb、Cu、Zn、Hg含量越高。内梅罗综合污染指数表明,研究区综合污染指数为11.2,为重污染,单因子污染指数和地质累积指数表明,研究区土壤Cd污染最严重,其次是As、Zn、Pb、Cu、Hg污染,Cr和Ni无污染。相关性分析和主成分分析表明,Cd、Hg、As、Pb、Zn之间存在显著正相关关系,主要受铅锌尾矿库长期堆存、转运及加工等人为活动影响,Cr、Ni主要来自土壤母质,Cu主要受矿业活动和农业活动共同影响。     

煤炭矿区排矸场表层土壤重金属污染研究

采用填埋覆土的方式对煤矸石进行处理,在沉陷区沟壑地带分层充填矸石,使沟地变为平地,对环境保护有重要意义。神府东胜煤田的大多数煤矿现已基本采用填埋覆土的方式对煤矸石进行处理。以神府东胜煤田中某排矸场为研究对象,分析了排矸场表层土壤（地表及-1 m处）中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn含量的空间分布特征及土壤中重金属的赋存形态。研究表明,排矸场中As、Cd、Cr、Cu、Pb、Zn含量超过该地区的土壤背景值,对当地的土壤环境造成了一定的污染;排矸场土壤中As、Cd、Cr、Cu、Mn、Ni、Pb在-1 m处的含量高于表层土壤,并且排矸场中-1 m处土壤的8种重金属元素的含量都高于对照区土壤重金属含量;排矸场中Cd、Cr、Cu、Ni残渣态占比最大,As可氧化态占比最大,Mn、Zn、Pb可交换态和可还原态占比较大,Mn、Zn、Pb以更不稳定的形态存在,对生态环境影响较大。     

菖蒲和芦苇对复合重金属胁迫的生理反应及其富集能力

研究了水生植物菖蒲和芦苇对复合重金属(V、Cr和Cd)的富集能力及对重金属的生理响应,以考察这两种植物对重金属污染水体的修复效果.结果表明,随着水体中重金属污染浓度的提高,两种植物的耐性系数均有所下降,但菖蒲的生长状况优于芦苇.在不同重金属污染浓度下,菖蒲和芦苇均表现出对Cd的富集能力最强,其次是Cr,而对V的富集能力相对较弱.在相同重金属浓度下,菖蒲对三种重金属的富集总量大于芦苇,在重金属质量浓度为15 mg·L-1时,菖蒲对三种重金属的富集量分别是1065.02、1754.80和4372.40 mg·kg-1,且菖蒲地下部分对V、Cr和Cd的富集系数分别是芦苇的2.1倍、1.5倍和1.8倍.综合考虑得出菖蒲比芦苇更适用于V、Cr和Cd复合重金属污染的修复.      

密闭酸溶-电感耦合等离子体质谱法测定道路扬尘中铜铅锌镉铬镍砷

准确测定道路扬尘样品中重金属元素Cu、Pb、Zn、Cd、Cr、Ni、As,对于城市道路环境污染的防治工作来说意义重大。采用HF-HNO₃体系密闭酸溶法消解样品,选择⁵²Cr、⁶⁰Ni、⁶³Cu、⁶⁶Zn、⁷⁵As、¹¹¹Cd、²⁰⁸Pb为测量同位素,采用He气模式的碰撞反应池技术测定Cr和As,采用仪器自带干扰校正公式对Cd的测定结果进行校正,建立了电感耦合等离子体质谱法(ICP-MS)测定道路扬尘样品中Cu、Pb、Zn、Cd、Cr、Ni、As的方法。重点对溶样条件进行了优化,结果表明,在0.1 g样品中加入7.0 mL由HF和HNO₃按照体积比为1︰6组成的混合酸,于160 ℃密闭溶解2 h可将样品溶解完全。在优化的实验条件下,校准曲线的相关系数均大于0.999,检出限为0.012~0.096 μg/g,定量限为0.040~0.32 μg/g。将实验方法应用于道路扬尘样品中Cu、Pb、Zn、Cd、Cr、Ni、As的测定,并进行加标回收试验,结果的相对标准偏差(RSD,n=12)均小于4%,加标回收率为95%~104%。采用实验方法对道路扬尘样品进行分析,测定结果与高压微波消解-ICP-MS法测定Cu、Pb、Zn、Cd、Cr、Ni,氢化物发生原子荧光光谱法(HG-AFS)测定As的结果基本吻合。     

Hydraulic Conductivity and Leachate Characteristics of Stabilized Fly Ash

Disposal of fly ash on land amounts to sacrificing precious land space. Recycling of fly ash is one of the methods of solving the disposal problem. Stabilization of a low lime fly ash with lime and gypsum was studied through large scale tests on the stabilized material designed to simulate field recycling conditions as closely as possible, and found to be a very effective means to control hydraulic conductivity and leachate characteristics. The effects of moulding water content, lime content, gypsum content, curing period, and flow period on hydraulic conductivity, and on leachate of metals flowing out of the stabilized fly ash are reported herein. With proper proportioning of the mix, and adequate curing, the values of hydraulic conductivity on the order of 10?7 cm∕s were achieved. The concentrations of As, Cd, Cr, Cu, Fe, Hg, Mg, Ni, Pb, and Zn in the effluent emanating from the hydraulic conductivity specimens of mixes with higher proportions of lime or lime and gypsum were below threshold limits acceptable for contaminants flowing into ground water.     

冷水江锑矿废弃地乡土树种重金属富集能力研究

采集并分析了冷水江锑矿区废弃地乡土树种及其根际土壤重金属含量,研究了树种对重金属的富集和转运特征。结果表明:矿区废弃地土壤中Cd含量超出国家土壤污染风险筛选值(GB 15618—2018),Sb含量是全国土壤背景值的104~226倍,以Cd、Sb重污染为主,伴有As、Hg、Pb复合污染。采集的8种乡土树种均对重金属元素表现出一定的耐受性,柏木、楸树对Hg、Cd和Sb的富集与运转能力较强;构树对Pb、Hg、Cd和Sb的富集与运转能力较强;南酸枣对Hg、Cd和Sb富集能力强,Cd、Sb运转能力较弱;七里香、梓树、棕榈和大叶女贞对Hg、Cd富集与运转能力强。根据废弃地重金属污染情况与树种对重金属的富集系数、运转系数,得出柏木、楸树、南酸枣和构树适合作为锑矿区废弃地植物修复的优选树种。