不同部位梧桐生物质炭对水溶液中镉吸附的机理

为了探究梧桐不同部位废弃物所制备的生物质炭(皮、枝、叶)对Cd²⁺的吸附效率和稳定修复的机理,以此为园林废弃物炭化利用在重金属污染修复方面的应用提供科学依据.利用实验室模拟法,通过高温煅烧法制备梧桐不同部位生物质炭,采用元素分析仪、比表面积及孔隙分析(BET)、X射线衍射仪(XRD)、扫描电镜/能谱(SEM/EDS)及衰减全反射红外光谱(ATR-IR)等技术研究不同反应时间、重金属浓度和溶液初始pH条件下生物质炭对Cd²⁺吸附效果的影响,并运用四步萃取法和脱附实验分析生物质炭上Cd²⁺的吸附形态和稳定性.3种生物质炭都在8 h左右达到吸附平衡,最终吸附量依次为树皮炭>枝条炭>叶片炭;溶液初始浓度为0.5—2 g·L^-1时Cd²⁺的吸附量呈增长趋势,在2.5—3g·L^-1时逐渐平缓;生物质炭Cd²⁺吸附量均随着pH的升高而升高,但在pH值为5—8时,吸附的趋势逐渐平稳;树皮炭的酸溶态和非生物利用态的稳定Cd形态要高于枝条炭和叶片炭;比表面积不是影响梧桐生物质炭吸附Cd²⁺的主要影响因素,吸附动力学,ATR,XRD和重金属形态萃取均证实Cd碳酸盐类矿物生成是主导吸附机理;3种生物质炭的脱附量在4 h后逐渐趋于平衡,其中脱附量最大为叶片炭,最小为树皮炭.梧桐不同部位的初始性质对生物质炭吸附Cd²⁺具有明显的影响,其中梧桐皮具备更高的吸附量和重金属稳定形态,并且相比其他种类生物质炭有明显优势.因此,从吸附效果和生产成本的角度,本研究建议以梧桐皮为主,枝条和叶片为辅的生物质炭对重金属Cd进行修复治理.

Mechanism of cadmium adsorption by biochar from different parts of platanus acerifolia in aqueous solution

To explore the adsorption efficiency of Cd²⁺ by biochar(bark,branch and leaf)prepared from Wutong waste from different components and the mechanism of repair stability,and provide scientific basis for the application of carbonization of garden wastes in heavy metal pollution remediation.The biochar made from different platanus acerifolia components was prepared by means of laboratory simulation and calcined at high temperature.The effects of reaction time,heavy metal concentration and initial pH on the adsorption of Cd²⁺by biochar were studied by elemental analyzer,specific surface area and pore analyzer(BET),X ray diffractometer(XRD),scanning electron microscopy/energy dispersive spectrometry(SEM/EDS)and attenuated total reflectance infrared spectroscopy(ATR-IR).Four step extraction method and desorption experiment were used to analyze the adsorption form and stability of Cd²⁺on biochar.All the three biochar reached adsorption equilibrium at about 8 h and the final adsorption amount was bark biochar>branch biochar>leaf biochar;When the initial concentration of Cd²⁺solution was 0.5—2 g·L^-1,the adsorption amount of Cd²⁺by biochar showed an increasing trend and gradually flattens out at 2.5—3 g·L^-1;The adsorption of Cd²⁺on biochar increased with the increase of pH,but the adsorption trend gradually stabilized at pH 5—8;The acid soluble and abiotic utilization of Cd speciation in bark biochar were more stable than that in branch biochar and leaf biochar.The specific surface area was not the main factor affecting the adsorption of platanus acerifolia biochar,adsorption kinetics,ATR,XRD and heavy metal speciation confirmed that the formation of Cd-carbonate minerals is the dominant adsorption mechanism.The desorption amount of the three biochar tended to balance gradually after 4 h.The maximum desorption amount was leaf biochar and the minimum was bark biochar.Different platanus acerifolia components had obvious effects on Cd²⁺adsorption by biochar.The bark biochar had higher adsorption capacity and stable form of heavy metals and it had significant advantages over other biochar species.Therefore,from the perspective of adsorption effect and production cost,this study suggested that biochar should be prepared mainly from bark,supplemented by branches and leaves,and use it to repair and remediation Cd pollution.