新型多孔生物质铁炭基功能材料高效去除镉及其作用机制

通过高温厌氧碳热还原方法制备出一种新型多孔生物质铁炭基功能材料,并详细分析了材料的结构和性质;考察了制备过程中的热解温度、pH和干扰离子等环境因子对镉吸附性能的影响,并揭示了铁炭基功能材料对镉的固定机制。结果表明,材料比表面积和孔容随热解温度升高而增加,在800 ℃材料中形成了纳米零价铁和碳化铁,制备出了具有磁性的铁炭基功能材料(MCFe-800),有利于材料的磁性回收。动力学实验结果表明,MCFe-800对水体镉的去除率明显高于其他热解温度,最大吸附容量归一化到铁为463.84 mg·g⁻¹。在偏中性条件下更有利于对镉的去除。MCFe-800对镉的固定机制主要为静电吸附、共沉淀和表面络合。此外,经过4次循环实验后,MCFe-800对实际水体中镉的去除率仍为75.0%。滤柱实验结果表明,当镉初始质量浓度为1 000 μg·L⁻¹和2 000 μg·L⁻¹时,有效处理量分别为400 BV和270 BV。因此,新型多孔生物质铁炭基功能材料在水体镉污染修复方面具有很大应用潜力。     

生物炭对土壤吸附邻苯二甲酸二乙酯的影响

选择花生壳为原材料,采用限氧升温法在450、700℃温度下分别热解2、4、6 h制备6种生物炭,在对其表面性质和元素组成进行分析的基础上,重点考察生物炭对土壤吸附邻苯二甲酸二乙酯（diethyl phthalate,DEP）的影响。结果表明：生物炭的比表面积和总孔体积随着热解温度的升高而增加,热解时间的延长也会提高比表面积和总孔体积,而4 h是较为适宜的热解时间;生物炭中元素组成主要受热解温度的影响,热解时间的作用很小,热解温度的升高使生物炭的芳香性增强,极性降低;添加生物炭能显著提高土壤对DEP的吸附能力;Langmuir模型和Freundlich模型均能较好地拟合添加生物炭土壤对DEP的吸附特征;在不同的平衡浓度条件下,生物炭对土壤吸附DEP的贡献率介于82.07%~99.49%之间,表明生物炭对土壤中DEP的吸附发挥着主导作用。相关分析发现,吸附参数ΔKoc与生物炭的比表面积和总孔体积具有显著相关性,提高比表面积和改善孔隙结构可以增强生物炭对DEP的吸附能力。     

Arsenic sorption by red mud-modified biochar produced from rice straw

Red mud-modified biochar (RM-BC) has been produced to be utilized as a novel adsorbent to remove As because it can effectively combine the beneficial features of red mud (rich metal oxide composition and porous structure) and biochar (large surface area and porous structure properties). SEM-EDS and XRD analyses demonstrated that red mud had loaded successfully on the surface of biochar. With the increasing of pH in solution, arsenate (As(V)) adsorption on RM-BC decreased while arsenite (As(III)) increased. Arsenate adsorption kinetics process on RM-BC fitted the pseudo-second-order model, while that of As(III) favored the Elovich model. All sorption isotherms produced superior fits with the Langmuir model. RM-BC exhibited improved As removal capabilities, with a maximum adsorption capacity (Q_max) for As(V) of 5923 μg g^?1, approximately ten times greater than that of the untreated BC (552.0 μg g^?1). Furthermore, it has been indicated that the adsorption of As(V) on RM-BC may be strongly associated with iron oxides (hematite and magnetite) and aluminum oxides (gibbsite) by X-ray absorption near-edge spectroscopy (XANES), which was possibly because of surface complexation and electrostatic interactions. RM-BC may be used as a valuable adsorbent for removing As in the environment due to the waste materials being relatively abundant.     

生物碳和土壤性质对乙草胺吸附行为的影响

生物碳施加到土壤中可能会影响污染物的环境归趋,而吸附作用是其关键控制因素,为此,本研究考察了400、500和600℃下制备的玉米秸秆生物碳(分别记作CS400、CS500和CS600)和土壤性质对乙草胺吸附行为的影响。结果表明,生物碳和土壤对乙草胺的吸附等温线符合Freundlich模型(R2≥0.99)。随着生物碳热解温度的升高(从CS400到CS600),生物碳吸附乙草胺的非线性指数n值减小且logKOC值增大,说明吸附非线性程度和吸附能力增强,这是因为生物碳炭化程度增强(H/C原子比减小),疏水性增强(O/C原子比减小)和比表面积增大而有利于对乙草胺的吸附,吸附机制以表面吸附为主(比如疏水作用、π-π EDA作用和孔填充作用)。然而,土壤吸附乙草胺的n值(0.95)接近1.0,说明该吸附作用几乎是线性吸附,以分配作用机制为主。3种生物碳对乙草胺的吸附能力都高于土壤,特别是CS600对乙草胺的吸附能力(logKOC)比土壤及文献报道的土壤和沉积物高一个数量及以上,说明生物碳可能会有效保留土壤中的乙草胺而降低其迁移性。     

生物炭对Cd污染土壤的修复效果与机理

通过修复培养实验和BCR连续提取实验研究牛粪生物炭（DM）和水稻秸秆生物炭（RS）对2种镉污染土壤的修复效果、影响因素及修复后的Cd的形态分布,探讨可能存在的修复机理。经56 d修复后,与CK相比,5%添加量的牛粪生物炭（DM5%）和水稻秸秆生物炭（RS5%）使TCLP提取态Cd在S1土壤中分别降低了15%和18%,在S2土壤中分别降低了5%和6%。但生物炭添加量为1%时对S2土壤中Cd无显著修复效果。DM5%和RS5%处理使Cd的酸可溶态在S1土壤中降低8.66%和9.25%,在S2土壤中降低7.86%和13.4%,相应的残渣态在S1土壤中升高8.30%和10.54%,在S2土壤中升高8.67%和14.92%。同时,DM5%和RS5%处理使土壤pH提高了7.69%~13.13%,TCLP提取态P增高了0.046~0.39 mg·g-1。结果表明,添加量为5%的牛粪生物炭和秸秆生物炭可有效修复Cd污染土壤。     

Comparative assessment of metribuzin sorption efficiency of biochar,hydrochar and vermicompost

Abstract

In this study, we used two biochars (BC) produced from grapevine pruning residues (BCgv) and red spruce wood (BCrs), two hydrochars (HC) from urban pruning residues (HCup) and the organic fraction of municipal solid wastes (HCuw), and two vermicomposts (VC) obtained vermicomposting digestates from buffalo manure (VCbm) and mixed feedstock (VCmf). Adsorption kinetics and isotherms of metribuzin onto these materials were performed. Sorption kinetics followed preferentially a pseudo-second-order model, thus indicating the occurrence of chemical interactions between the sorbate and the adsorbents. Adsorption constants were calculated using the Freundlich and Langmuir models. Metribuzin sorption data on BCgv and both HC fitted preferentially the Freundlich equation, whereas on the other materials data fitted both isotherms well (r?>?0.95). Metribuzin sorption capacity of the materials followed the trend BC?>?HC?>?VC. Sorption constants of metribuzin normalised per organic carbon content (K_OC) on BCgv, BCrs, HCup, HCuw, VCbm and VCmf were 561, 383, 251, 214, 102 and 84?L kg^?1, respectively. A significant positive correlation (P?=?0.016) was calculated between distribution coefficients (K_d) of all materials and the corresponding organic carbon contents, thus indicating a prominent role of the organic fraction of these materials in the adsorption of metribuzin.     

Effect of culturing temperatures on cadmium phytotoxicity alleviation by biochar

Biochar produced from rice straw at 400 °C (RS400) was prepared to determine its alleviating effect on Cd phytotoxicity to wheat seedlings under different cultivation temperatures and pH. A hydroponic system (pH 4.3) and a loam soil slurry system were designed to respectively simulate acidic and neutral soil condition, and cultivation at increasing temperatures (20, 25, and 30 °C) were performed to evaluate the greenhouse effect. The root and shoot elongation and the Cd concentration in root and solution were measured; furthermore, batch experiments for Cd adsorption were undertaken. An increasing inhibition of the root by Cd addition was observed at increasing temperatures. The inhibition rate was 50.50 and 20.80% in hydroponic system and slurry system at 25 °C, respectively; however, the corresponding inhibition rates of root were significantly decreased to 25.5 and 3.5% with addition of RS400. This is mainly attributed to the reduction of Cd migration into the roots by RS400, which decreased Cd bioavailability. The mechanism behind the reduced Cd bioavailability is attributed to the Cd adsorption and the strong buffering capacity of acidity by RS400. Therefore, biochar could be a potential amendment for the remediation of Cd-contaminated soil even at increasing culturing temperatures.

     

化学淋洗与生物质炭稳定化联合修复镉污染土壤

为探讨土壤淋洗与生物质炭稳定化联合修复技术对镉（Cd）污染黄棕壤修复效果的影响,研究通过振荡淋洗实验、BCR 连续化学提取法和CaCl2 一次提取法,筛选确定污染土壤的最佳淋洗方案,并比较了淋洗修复、淋洗 + 稳定化修复技术对污染土壤中Cd生物有效性的影响。结果表明：3种淋洗剂的淋洗效率强弱顺序为EDTA-2Na>HCl> 柠檬酸,最佳淋洗条件为0.12 mol·L-1 EDTA-2Na在固-液比1:4条件下振荡淋洗3h,Cd的洗脱率为81.3%;淋洗后土壤中Cd的有效态（F1+F2）百分比减少了51.0%,显著降低了污染土壤的重金属总量及其环境风险;相比于单一淋洗修复技术,EDTA-2Na在添加体积（V添加）为最佳淋洗体积（V最优）的80%时,淋洗后再加入3%玉米秸秆炭稳定化15 d的联合修复技术能够将土壤中有效态Cd含量（CaCl2-Cd）从8.13 mg·kg-1降低到0.42 mg·kg-1。因此,淋洗修复后施加玉米秸秆炭的联合修复技术,能够有效降低重金属污染土壤的生态环境风险,提高土壤环境质量。     

Sequential sorption of lead and cadmium in three tropical soils

It is important to examine mechanisms of Pb and Cd sorption in soils to understand their bioavailability. The ability of three tropical soils to retain Pb, Cd, and Ca was evaluated. The objectives of this study were to (1) determine the extent to which soil sorption sites are metal specific, (2) investigate the nature of reactions between metals and soil surfaces, and (3) identify how metals compete for sorption sites when they are introduced to soils sequentially or concurrently. Lead was shown to be much less exchangeable than Cd and inhibited Cd sorption. Cadmium had little effect on Pb sorption, though both Ca and Cd inhibited the adsorption of Pb at exchange sites. Lead appears to more readily undergo inner-sphere surface complexation with soil surface functional groups than either Cd or Ca. Thus, regardless of when Pb is introduced to a soil, it should be less labile than Cd.     

Use of biochar for the sorption of volatile organic compounds (VOCs) emitted from cattle manure

Environmental Science and Pollution Research - The ability of biochar to be used as filter or as additive for the adsorption of volatile organic compounds (VOCs) emitted from cattle manure is...     

New insights into the sorption mechanism of cadmium on red mud

Effectiveness and mechanism of cadmium (Cd) sorption on original, acidified and ball milling nano-particle red muds were investigated using batch sorption experiments, sequential extraction analysis and X-ray absorption near edge structure (XANES) spectroscopy. The maximum sorption capacity of Cd was 0.16, 0.19, and 0.21 mol/kg for the original, acidified, and nano-particle red muds at pH 6.5, respectively. Both acidification and ball-milling treatments significantly enhanced Cd sorption and facilitated transformation of Cd into less extractable fractions. The Cd L_III-edge XANES analysis indicated the formation of inner-sphere complexes of Cd similar to XCdOH (X represents surface groups on red mud) on the red mud surfaces although outer-sphere complexes of Cd were the primary species. This work shed light on the potential application of red mud to remediate Cd-contaminated soils and illustrated the promising tool of XANES spectroscopy for speciation of multicomponent systems of environmental relevance.     

污泥基生物炭吸附重金属Cd的动力学和热力学

炭化是污泥资资源化利用的重要途径。研究了污泥基生物炭对Cd的吸附过程,探讨了污泥基生物炭吸附重金属Cd的动力学和热力学特征。结果显示污泥基生物炭对Cd的吸附符合准二级动力学方程。Freundlich方程能较好的模拟吸附等温线。随着温度增加,吸附呈现逐渐增强趋势。吸附热力学结果显示35℃时吸附并非自发进行,随着温度增加,吸附转为吸热并自发进行。污泥基生物炭对Cd的吸附主要以化学吸附为主,同时存在多种机制共同作用。研究结果表明污泥基生物炭有作为重金属Cd污染废水修复剂的潜力。     

镉和磷酸根离子在铝柱撑膨润土上的协同吸附

羟基金属柱撑粘土矿物表面带有大量强反应活性的羟基金属基团,因而对重金属阳离子和和含氧酸根阴离子都具有很好的吸附能力,相关研究特征也有大量研究报道。但实际环境中重金属阳离子和和含氧酸根阴离子往往共存,而它们在柱撑粘土上同时吸附的特征则鲜有研究报道。以铝柱撑膨润土(Al-Bent)为柱撑粘土代表,研究了重金属阳离子Cd2+和含氧酸根阴离子磷酸根(H2PO-4)共存条件下2种污染物在Al-Bent上的吸附特征。研究结果显示,Cd2+和H2PO-4在Al-Bent上具有协同吸附效应,即共存离子可以促进Al-Bent对另一污染物的吸附性能。吸附过程的p H变化特征表明,Cd2+主要通过与铝羟基上的H交换被吸附,H2PO-4则与铝羟基上的羟基交换被吸附;而两者共同吸附时,则可形成AlPO4-Cd三元络合物。XPS研究结果进一步证实了在Al-Bent上生成了三元络合物。因此,羟基金属柱撑粘土作为多功能吸附剂可用于含重金属阳离子和含氧酸根阴离子的复杂废水的处理。     

The immobilisation and retention of soluble arsenic, cadmium and zinc by biochar

Water-soluble inorganic pollutants may constitute an environmental toxicity problem if their movement through soils and potential transfer to plants or groundwater is not arrested. The capability of biochar to immobilise and retain arsenic (As), cadmium (Cd) and zinc (Zn) from a multi-element contaminated sediment-derived soil was explored by a column leaching experiment and scanning electron microanalysis (SEM/EDX). Sorption of Cd and Zn to biochar’s surfaces assisted a 300 and 45-fold reduction in their leachate concentrations, respectively. Retention of both metals was not affected by considerable leaching of water-soluble carbon from biochar, and could not be reversed following subsequent leaching of the sorbant biochar with water at pH 5.5. Weakly water-soluble As was also retained on biochar’s surface but leachate concentrations did not duly decline. It is concluded that biochar can rapidly reduce the mobility of selected contaminants in this polluted soil system, with especially encouraging results for Cd.     

Effects of biowaste-derived biochar on the dynamic behavior of cadmium fractions in soils

Environmental Science and Pollution Research - As a commonly used amendment to soil contaminated by heavy metals, biochar has attracted great attention and has been applied for decades due to the...     

KOH活化制备蚕沙基生物炭及其对镉的吸附特性

以蚕沙生物炭为原料,以KOH为活化剂,通过浸渍(KBC)和浸渍-热解(KBC400)活化工艺制备蚕沙基生物炭,用于吸附去除水体中的镉离子(Cd2+).运用一系列的表征技术分析了生物炭的形貌和性质,并通过批量实验考察了投加量、pH、共存离子、吸附时间和Cd2+浓度等因素对Cd2+吸附性能的影响.表征实验结果表明,活化的蚕...     

土壤颗粒级配对镉吸附-解吸规律的影响

利用甘肃金川某地土壤通过批实验进行等温吸附和动力学解吸实验,研究不同颗粒级配的中砂对镉的吸附、解吸特征,并采用Freundlich和一级动力学方程对其吸附解吸方程进行拟合。结果表明,(1)Freundlich和一级动力学方程对该土壤吸附、解吸镉的实验适用;(2)等温吸附实验中4组不同颗粒级配的中砂对镉的吸附性很强,最大平衡吸附量依次为260.667、286.107、299.362和292.232 mg/kg,吸附性能与颗粒级配中的细粒土相对含量大小成正比;(3)4组土壤对镉的解吸在初期2 h内解吸速率均较快,在3 h左右达到吸附-解吸平衡。平衡后4组土样Ⅰ、Ⅱ、Ⅲ和Ⅳ的最大解吸量依次为0.752、0.561、0.44和0.54 mg/kg,解吸速率和平衡时最大解吸量均与颗粒级配中细颗粒相对含量密切相关。     

Impact of woodchip biochar amendment on the sorption and dissipation of pesticide acetamiprid in agricultural soils

Pyrolysis of vegetative biomass into biochar and application of the more stable form of carbon to soil have been shown to be effective in reducing the emission of greenhouse gases, improving soil fertility, and sequestering soil contaminants. However, there is still lack of information about the impact of biochar amendment in agricultural soils on the sorption and environmental fate of pesticides. In this study, we investigated the sorption and dissipation of a neonicotinoid insecticide acetamiprid in three typical Chinese agricultural soils, which were amended by a red gum wood (Eucalyptus spp.) derived biochar. Our results showed that the amendment of biochar (0.5% (w/w)) to the soils could significantly increase the sorption of acetamiprid, but the magnitudes of enhancement were varied. Contributions of 0.5% newly-added biochar to the overall sorption of acetamiprid were 52.3%, 27.4% and 11.6% for red soil, paddy soil and black soil, respectively. The dissipation of acetamiprid in soils amended with biochar was retarded compared to that in soils without biochar amendment. Similar to the sorption experiment, in soil with higher content of organic matter, the retardation of biochar on the dissipation of acetamiprid was lower than that with lower content of organic matter. The different effects of biochar in agricultural soils may attribute to the interaction of soil components with biochar, which would block the pore or compete for binding site of biochar. Aging effect of biochar application in agricultural soils and field experiments need to be further investigated.     

Effect of bamboo biochar on reducing grain cadmium content in two contrasting wheat genotypes

Environmental Science and Pollution Research - Wheat is the second most important food crop worldwide, which is prone to accumulate cadmium (Cd). Accumulation of Cd in wheat grains depends not only...     

Geochemical modeling of cadmium sorption to soil as a function of soil properties

Cadmium sorption experiments were conducted to infer Cd sorption mechanisms to a reference smectite and three fractions of a Vertisol soil. Untreated Vertisol has a higher adsorption capacity for Cd than that of reference smectite. Surface complex modeling was used to calculate the potential contributions of Cd complexation reactions with permanent charge sites and pH-dependent charge sites over ranges in pH, for soils with given surface areas, and sorption site densities. The Langmuir model produced relatively good predictions of Cd sorption on reference smectite and Vertisol. However, the results of the triple-layer model (TLM) were inadequate to describe Cd adsorption on fixed-charge sites because the model could not account for the ion-exchange reaction on the basal plane. Based upon the two geochemical models of Cd adsorption to the reference smectite and Vertisol, it appears that the basal plane siloxane cavities are the most important sites for Cd complexation at pH < 6.5. For the pH-dependent sites, the edge-site aluminol appears to be the dominant surface functional group responsible for Cd adsorption at pH > 6.5.