Co-pyrolysis of sludge and kaolin/zeolite in a rotary kiln: Analysis of stabilizing heavy metals

• Adding kaolin/zeolite promotes the formation of stable heavy metals. • The potential ecological risk index of co-pyrolysis biochar is extremely low. • Increasing the pyrolysis temperature reduces the leaching toxicity of heavy metals. • The toxicity of biochar reduces with the increasing content of stable heavy metals. Pyrolysis is a promising technique used for treating of sewage sludge. However, the application of pyrolysis products is limited due to the presence of heavy metals. In this study, sewage sludge mixed with kaolin/zeolite was pyrolyzed in a rotary kiln, aiming to improve the immobilization of heavy metals in pyrolytic carbon. The total concentrations, speciation distributions, leaching toxicities, and potential ecological risk indices of heavy metals in pyrolysis biochar were explored to examine the effects of kaolin/zeolite and pyrolytic temperature on immobilizing heavy metals. Further, mineral composition and surface morphology of biochar were characterized by X-ray diffraction and scanning electron microscopy to reveal the potential mechanism of immobilizing heavy metals. Increasing pyrolysis temperature facilitated the stabilization of heavy metals in pyrolysis biochar. The proportions of stable heavy metals in biochar obtained at 650℃ were 54.50% (Cu), 29.73% (Zn), 79.29% (Cd), 68.17% (Pb) and 86.70% (Cr). Compared to sewage sludge, the potential contamination risk index of pyrolysis biochar obtained at 650℃ was reduced to 17.01, indicating a low ecological risk. The addition of 7% kaolin/zeolite further reduced the risk index of co-pyrolysis biochar prepared at 650℃ to 10.86/15.28. The characterization of biochar revealed that increase in the pyrolysis temperature and incorporation of additives are conducive to the formation of stable heavy metal-inorganics. This study demonstrates that the formation of stable mineral compounds containing heavy metals is the key to stabilizing heavy metals in pyrolysis biochar.     

Sorption mechanisms of diphenylarsinic acid on natural magnetite and siderite: Evidence from sorption kinetics,sequential extraction and extended X-ray absorption fine-structure spectroscopy analysis

• DPAA sorption followed pseudo-secondary and intra-particle diffusion models. • Chemical bonding and intra-particle diffusion were dominant rate-limiting steps. • DPAA simultaneously formed inner- and outer-sphere complexes on siderite. • DPAA predominantly formed occluded inner-sphere complexes on magnetite. • Bidentate binuclear bond was identified for DPAA on siderite and magnetite. Diphenylarsinic acid (DPAA) is both the prime starting material and major metabolite of chemical weapons (CWs). Because of its toxicity and the widespread distribution of abandoned CWs in burial site, DPAA sorption by natural Fe minerals is of considerable interest. Here we report the first study on DPAA sorption by natural magnetite and siderite using macroscopic sorption kinetics, sequential extraction procedure (SEP) and microscopic extended X-ray absorption fine-structure spectroscopy (EXAFS). Our results show that the sorption pseudo-equilibrated in 60 minutes and that close to 50% and 20%–30% removal can be achieved for magnetite and siderite, respectively, at the initial DPAA concentrations of 4–100 mg/L. DPAA sorption followed pseudo-secondary and intra-particle diffusion kinetics models, and the whole process was mainly governed by intra-particle diffusion and chemical bonding. SEP and EXAFS results revealed that DPAA mainly formed inner-sphere complexes on magnetite (>80%), while on siderite it simultaneously resulted in outer-sphere and inner-sphere complexes. EXAFS analysis further confirmed the formation of inner-sphere bidentate binuclear corner-sharing complexes (²C) for DPAA. Comparison of these results with previous studies suggests that phenyl groups are likely to impact the sorption capacity and structure of DPAA by increasing steric hindrance or affecting the way the central arsenic (As) atom maintains charge balance. These results improve our knowledge of DPAA interactions with Fe minerals, which will help to develop remediation technology and predict the fate of DPAA in soil-water environments.     

BiPO4/赤铁矿光催化降解气态苯乙烯

利用水热法合成了 BiPO₄/赤铁矿复合催化剂,并对催化剂进行了 X 射线衍射（XRD）、扫描电镜（SEM）、X 射线光电子能谱（XPS）、透射电子显微镜（TEM）、紫外可见漫反射（DRS）、BET 比表面及光致发光光谱（PL）等一系列表征,同时探讨了不同制备条件下的复合催化剂对气态苯乙烯降解的影响及其光催化机理 .结果表明：天然赤铁矿的负载能有效提高 BiPO₄光生电子-空穴对的分离效率,提升其光催化活性;当制备BiPO₄/赤铁矿的条件为质量比1∶1、溶液 pH=1、焙烧温度 300 ℃时,复合材料对 50 mg·m^-3气态苯乙烯的降解率最高,达到 87.9%,且在同等条件下进行 4 次循环实验后,降解率仅下降 5.9%,稳定性得以证明 . 经过机理实验研究证明,BiPO₄/赤铁矿复合催化剂光催化降解苯乙烯主要是光生电子-空穴对、氧衍生的超氧自由基及羟基自由基起主导作用 .     

水源水水质风险评价的讨论及实例——以南方N市为例

水质风险评价是环境风险评价的重要组成部分。文章从数据收集以及评估、有毒性评价、暴露评价、风险表征等四个方面,探讨了以长江水为饮用水源水的N市水质健康风险评价体系的构建,并利用相关数据进行分析讨论。结果表明,水源水体中致癌物质六价铬、砷的风险值较高,镉的风险值虽未超标但也已经接近国际标准;非致癌物质氟化物、铅、铁、氨氮、汞、氰化物、锰、挥发酚的非致癌风险都低于国际水平;水源水中11项污染物的危害指数排序为:砷氟化物六价铬铅镉铁氨氮汞氰化物锰挥发酚,其绝对值大部分都超过了1。     

序批式反应器工艺的研究进展

回顾了序批式反应器(SBR)技术的发展历史，介绍了近20年来国内外SBR技术研究与应用的新发展，着重分析了其基本原理、技术优势和不足之处，指出SBR技术是一项极具竞争力的废水生物处理技术。     

共生细菌SB1降解聚乙烯醇的研究--Ⅰ.共生细菌SB1的分离及某些性质

聚乙烯醇(PVA)是一种人工合成的水溶性大分子有机化合物。它广泛应用于纺织、化工和造纸等行业,随着化学合成技术的迅速发展,含这类物质的废水治理问题将日趋紧迫。七十年代以来国外已分离出降解PVA的菌株并用其净化环境。进入八十年代,国内在这方面也开始研究。本文报道的是共生细菌SB_1分离过程及其降解PVA的某些性质。     

多氯联苯的微生物降解

以多氯联苯(PCB)为唯一碳源,通过选择性富集培养,从变电站变压器油污染的土样中分离出25株PCB降解菌,底物生长试验结果表明,它们可以利用多种PCB作为唯一碳源,对其中三株菌作了鉴定,都属于假单胞菌属(Pseudomonas)用气相色谱法和氯离子测定法检测了八株菌对各种PCB的降解能力,降解率一般为20—50%,高的可达60—100%,降解能力随含氯量的增高而降低,不同异构体降解的难易程度有很大差别,在PCB的降解中有氯离子的释放。     

岸边带生态系统研究进展

水环境恶化,水资源紧缺是全球共同面临的重大环境问题之一,合理进行水资源的开发利用和水环境的管理是当前国际研究的热点.岸边带作为重要的水陆交错带,无论从经济评估角度还是生态学、景观学或者社会科学等方面对人类社会环境都具有重要的作用.国内外大量研究表明:岸边带生态系统具有廊道功能、缓冲功能和植被护岸功能,尤其在非点源污染和土壤侵蚀防治方面具有不可替代的作用.当前,岸边带理论在生态学、景观修复与管理领域仍然是科学前沿,从岸边带的定义、岸边带的结构、岸边带的管理系统理论和模型及岸边带系统的保护和恢复几方面对当前国内外岸边带的研究情况进行介绍.     

多氯联苯降解菌Pcb6所含质粒的某些特性的研究

研究证明,某些土壤微生物可以分解多氯联苯(PCBs)。笔者也曾报道过几株能够降解PCBs的细菌。细菌降解质粒可赋予细菌分解代谢各种复杂有机化合物的能力。Kamp和Furukawa等曾分别发现了能够将4-氯联苯和3,5-二氯联苯转化成对应的氯苯甲酸的质粒。 Pseudo monas.sp.Pcb6是一株含有质粒的PCBs降解菌,它对4-PCB、PCB-42、PCB-48和Aroclor1254降解效果显著,并具有明显的脱氯作用。本实验对该质粒的某些生物学特性进行了研究。     

湖泊沉积物有机碳的仪器分析法

通过条件实验，确定影响含碳酸盐湖泊沉积物有机碳分析的主要因素是清洗操作和空气中吸湿恒重操作。真空干燥法与清洗烘干法的结果一致。较合理的有机碳分析是用约４０～６０倍体积的１Ｎ盐酸在超声振荡作用下将无机碳清除，过滤清洗至无氯离子，并在分析前于空气中吸湿平衡，所用样品重量之差应小于５％，分析相对误差为±１４％。