Remediation of arsenic contaminated soil by sulfidated zero-valent iron

• Sulfidation significantly enhanced As(V) immobilization in soil by zerovalent iron. • S-ZVI promoted the conversion of exchangeable As to less mobile Fe-Mn bound As. • Column test further confirmed the feasibility of sulfidated ZVI on As retention. • S-ZVI amendment and magnetic separation markedly reduced TCLP leachability of As. In this study, the influences of sulfidation on zero-valent iron (ZVI) performance toward As(V) immobilization in soil were systemically investigated. It was found that, compared to unamended ZVI, sulfidated ZVI (S-ZVI) is more favorable to immobilize As(V) in soil and promote the conversion of water soluble As to less mobile Fe-Mn bound As. Specifically, under the optimal S/Fe molar ratio of 0.05, almost all of the leached As could be sequestrated by>0.5 wt.% S-ZVI within 3 h. Although the presence of HA could decrease the desorption of As from soil, HA inhibited the reactivity of S-ZVI to a greater extent. Column experiments further proved the feasibility of applying S-ZVI on soil As(V) immobilization. More importantly, to achieve a good As retention performance, S-ZVI should be fully mixed with soil or located on the downstream side of As migration. The test simulating the flooding conditions in rice culture revealed there was also a good long-term stability of soil As(V) after S-ZVI remediation, where only 0.7% of As was desorbed after 30 days of incubation. Magnetic separation was employed to separate the immobilized As(V) from soil after S-ZVI amendment, where the separation efficiency was found to be dependent of the iron dosage, liquid to soil ratio, and reaction time. Toxicity characteristic leaching procedure (TCLP) tests revealed that the leachability of As from soil was significantly reduced after the S-ZVI amendment and magnetic separation treatment. All these findings provided some insights into the remediation of As(V)-polluted soil by ZVI.     

磁性铁基改性生物炭去除水中氨氮

氨氮的过度排放是水体富营养化的一个重要原因.然而,随着环境法规的日益严格,传统方法处理效果难以达到要求.吸附法因高效、安全等优点近年来开始应用于去除水中的氨氮.本研究中以共沉淀法将磁性铁基材料负载到市政污泥生物炭上,结果表明其对水中氨氮有良好的去除效果.80℃下合成的材料（MB₈₀）在293 K下对氨氮的饱和吸附量可达17.52 mg·g^-1.动力学与热力学结果表明,MB₈₀吸附氨氮的过程更符合伪二级动力学和Langmuir等温线.MB₈₀对氨氮的吸附机制可归纳为静电吸引、孔隙填充、离子交换和氢键结合.且5次循环后对氨氮的吸附量仍十分理想,可达3.18 mg·g^-1.本研究的结果可以为高效去除水中氨氮提供一种行之有效的方法,并为市政污泥的处理提供新的出路.     

市政污泥热解过程中重金属迁移特性及环境效应评估

以昆明某市政污泥为原料,研究生物炭制备过程中重金属Fe、Zn、Mn和Ni的迁移特性,并基于其潜在环境风险确定污泥基生物炭制备的最佳热解温度.本实验选择总量较高的4种重金属Fe、Zn、Mn和Ni,采用BCR提取法测定不同热解温度下4种重金属的形态和含量变化,得到各金属的形态分布变化规律和迁移路径,利用潜在生态风险指数（PERI）和风险评估代码（RAC）对污泥基生物炭进行环境风险评估.结果表明,4种金属的易挥发程度排序为Zn > Mn > Fe > Ni,4种金属形态分布情况和变化规律各不相同,但迁移路径具有共通性.在低温热解阶段,不稳定形态向稳定形态转化;随着温度的升高,可氧化态和残渣态逐步分解破碎,部分逸散到大气中,部分形成可还原态.在环境风险评估方面,高温条件（>500℃）下制备的生物炭环境风险较低,500℃制备的生物炭经济性最好.     

浓度效应对卡马西平在生物炭上的吸附动力学影响

为了解人工合成药物在生物炭上的吸附动力学特征及其浓度效应的影响,选择卡马西平(CBZ)为目标污染物。探讨不同初始质量浓度(2、4、25、50 mg·L~(-1))在不同裂解温度(200、300、500℃)下制备的生物炭上的吸附动力学特征。结果表明,双室一级动力学模型可以精确地描述CBZ在生物炭上的吸附动力学特征。CBZ的快室吸附对总体吸附的贡献随初始浓度的增大而减小,而慢室吸附贡献则增大。π-π作用可能对CBZ的吸附贡献较大。孔隙填充可以描述慢室吸附过程,可能是吸附速率的控制环节。     

生物炭对菜地土壤氮平衡及酸碱缓冲能力的影响

针对太湖地区菜地化肥氮投入量较大导致氮淋失严重及土壤酸化的现状,选取太湖地区的菜地土壤,利用盆栽试验连续种植三季小白菜,结合生物炭埋袋回收技术,研究不同化肥氮施用量(以N计,0和110 mg/kg)及生物炭添加量(w为0%、1%、2%和5%)对土壤氮淋失及酸碱缓冲能力的影响. 结果表明:在化肥氮施用量为110 mg/kg条件下,与无生物炭添加相比,生物炭添加量为2%时可使作物对土壤矿质态氮的利用效率提高约1倍(由41%增至81%),因化肥氮施用引起的土壤氮素残留量降低83%;生物炭添加可有效减少48%~65%的土壤氮淋失量,当添加量为1%、2%时,生物炭主要通过削减淋失液中ρ(TN)来降低土壤氮淋失量;添加量为5%时,则主要通过削减淋失液体积来实现. 无论是否添加化肥氮,生物炭均能有效维持土壤原有的pH、w(有机质)及w(盐基离子);促使土壤酸碱缓冲能容量增加22%~37%,致酸速率降低17%~80%,显著提升了土壤的酸碱缓冲能力. 研究显示,在化肥氮施用量为110 mg/kg条件下,生物炭添加量为2%时能对土壤酸化产生较好的缓冲效果.      

Metal removal with two biochars made from municipal organic waste: adsorptive characterization and surface complexation modeling

The adsorptive characteristics of biochar produced from garden green waste (S-char) and a mixture of food waste and garden green waste (FS-char) were investigated. Adsorption of Cu²⁺, Zn²⁺, and Mn²⁺ onto the two biochars reached equilibrium within 48 hours. The metal adsorption was effectively described by the pseudo-second-order kinetic and Freundlich isotherm models which suggest heterogeneous chemisorption. The initial solution pH influenced adsorption of Zn²⁺ and Mn²⁺ but not of Cu²⁺. Simulation via a surface complexation model showed that the fraction of XOCu⁺ adsorbed onto biochar was increased with increasing pH until it reached the adsorption maximum at pH 8.5, while the endpoint for the maximum of XOMn⁺ was higher than pH 12.     

生物炭的土壤环境效应及其机制研究

近年来,随着土壤污染的逐渐加重以及食品安全问题的频出,生物炭作为重要的土壤改良剂以及对污染土壤修复表现出的巨大潜力引起人们的广泛关注.本文首先对国内外生物炭的土壤环境效应方面的研究以及成果进行分析总结.生物炭具有疏松多孔的性质以及巨大的表面积和阳离子交换量(CEC),可以改善土壤理化性质,能强烈吸附土壤中的污染物,降低其生物有效性和迁移转化能力;生物炭的碱性对于改良酸性土壤降低土壤中污染物的生物毒性具有很大的潜力;生物炭还可以为微生物提供生长繁殖的场所,有利于微生物对污染物的降解,但同时又可以保护被吸附的有机物免受微生物的降解,对不同的微生物影响不同;生物炭可以对蚯蚓等土壤动物的生存产生影响.在此基础上,依据生物炭的基本理化性质,对其土壤环境效应机制进行了分析.最后,从当前工作中存在的不足对今后的研究重点和方向进行了展望.     

One-pot preparation of graphene oxide magnetic nanocomposites for the removal of tetrabromobisphenol A

A simple solvothermal method was used to prepare monodisperse magnetite (Fe₃O₄) nanoparticles attached onto graphene oxide (GO) sheets as adsorbents to remove tetrabromobisphenol A (TBBPA) from an aqueous solution. These Fe₃O₄/GO (MGO) nanocomposites were characterized by transmission electron microscopy. The adsorption capacity at different initial pH, contact duration, and temperature were evaluated. The kinetics of adsorption was found to fit the pseudo-second-order model perfectly. The adsorption isotherm well fitted the Langmuir model, and the theoretical maximum of adsorption capacity calculated by the Langmuir model was 27.26 mg?g^-1. The adsorption thermodynamics of TBBPA on the MGO nanocomposites was determined at 303 K, 313 K, and 323 K, respectively. The results indicated that the adsorption was spontaneous and endothermic. The MGO nanocomposites were conveniently separated from the media by an external magnetic field within several seconds, and then regenerated in 0.2 M NaOH solution. Thus, the MGO nanocomposites are a promising candidate for TBBPA removal from wastewater.     

非均性多孔介质中生物炭胶体的迁移行为研究

生物炭颗粒在多孔介质中的迁移行为不仅决定了其在环境中的归趋,也极大地影响了被吸附污染物的环境行为.以往的研究主要集中在生物炭胶体在均性多孔介质中的迁移行为,但实际环境介质通常是非均性的,目前对生物炭胶体在非均性多孔介质中的迁移行为知之甚少.本研究采用两种不同粒径的石英砂构建了上下两层非均性填充柱（上层细颗粒,下层粗颗粒）,研究了生物炭胶体在非均性多孔介质中的迁移和截留行为,考察了溶液离子强度和pH对生物炭胶体迁移能力的影响.研究结果表明在非均性多孔介质中,生物炭胶体具有很高的迁移能力,在离子强度为1~50 mmol·L^-1,pH为4.0~11.0条件下,生物炭胶体的迁移率达40.2%~88.0%.非均性介质中生物炭胶体的截留曲线表现为非单调型曲线,截留量峰值往往出现在细-粗石英砂的交界面处（细石英砂侧）,这与非均性介质中显著的电荷异质性、介质尺寸异质性和迁移过程中传质通量异质性有关.生物炭胶体在上层细石英砂中的截留量显著大于其在下层粗石英砂中的截留量,表明上层细石英砂是影响生物炭胶体迁移行为的关键层.随着溶液离子强度增加,生物炭胶体自团聚作用增强,其与石英砂介质间界面作用能垒降低,因而生物炭胶体的迁移能力减弱.由于生物炭胶体与细石英砂间的物理张力作用趋于显著,增加离子强度提高了生物炭胶体在上层细石英砂中的截留比率.中性和碱性条件下生物炭胶体的迁移能力较强,而在酸性条件下,生物炭胶体表面电负性显著降低,团聚体粒径增大,生物炭胶体的迁移能力较弱.降低溶液pH增加了生物炭胶体在上层细石英砂中的截留比率.本研究的结果将有利于人们更好地了解生物炭胶体在复杂多孔介质中的迁移行为,为全面评估生物炭的潜在环境风险提供理论支持.     

硫脲改性猪粪生物质炭对模拟农田径流中镉和草甘膦吸附特征

为同时去除农田地表径流中的重金属和农药,利用猪粪制备未改性猪粪生物质炭（简称"未改性生物质炭"）和硫脲改性猪粪生物质炭（简称"改性生物质炭"）,分析比较硫脲改性对生物质炭的pH、元素组成、表面含氧官能团和巯基含量等理化性质的影响,并系统地研究了单一和复合污染体系中初始浓度对两种生物质炭吸附水溶液中镉（Cd）和草甘膦效率的影响.结果表明:①与未改性生物质炭相比,改性生物质炭的pH、O/C（原子比）和H/C（原子比）降低,比表面积增大,含氧官能团和巯基含量增加.②与未改性生物质炭相比,改性生物质炭对Cd和草甘膦的吸附能力增强,最大表观吸附量（Q_max）增加了近3倍;随着Cd和草甘膦初始浓度的增加,未改性和改性生物质炭对Cd和草甘膦的吸附量逐渐增加,增加量最高分别达18.52%和7.60%.③单一污染体系中两种生物质炭对Cd或草甘膦的吸附更符合Langmuir等温吸附模型,说明其对Cd或草甘膦的吸附机理是单分子层的吸附起主导作用.④复合污染体系中,未改性和改性生物质炭对Cd的吸附能力分别增加了25.28%和21.26%,未改性生物质炭对Cd的最大表观吸附量增加了29.34%,但改性生物质炭对Cd的最大表观吸附量降低了47.28%;未改性和改性生物质炭对草甘膦的吸附能力减弱,但最大表观吸附量分别增加了2.63和3.45倍.研究显示,硫脲改性猪粪生物质炭作为一项有前景的新技术,为解决实际环境中的复合污染问题提供了经济环保的技术手段.