银中杨、玉簪落叶生物质炭对Pb~(2+)、Cd~(2+)、Cr~(6+)吸附的影响因素

为探讨银中杨、玉簪落叶所制备生物质炭对水体Pb~(2+)、Cd~(2+)和Cr~(6+)吸附规律的差异及影响因素,采用限氧裂解法将银中杨及玉簪落叶制成生物质炭,并以此为吸附载体研究其在不同初始离子质量浓度、pH值、Na+浓度及接触时间等因素影响下对Pb~(2+)、Cd~(2+)和Cr~(6+)的吸附。结果表明:随着初始Pb~(2+)、Cd~(2+)和Cr~(6+)质量浓度的增加(0~800 mg·L~(-1)),落叶生物质炭对相应重金属离子的吸附量也增加。将初始质量浓度设置在0~200 mg·L~(-1),生物质炭对3种金属离子的吸附量由大到小表现为Pb~(2+)、Cd~(2+)、Cr~(6+),然而,将初始离子质量浓度提升至300~800 mg·L~(-1),吸附量由大到小表现为Pb~(2+)、Cr~(6+)、Cd~(2+);溶液pH值由2增至8,可使Pb~(2+)和Cd~(2+)在生物质炭表面的吸附率得到迅速提升,然而,生物质炭对Cr~(6+)的吸附率在整个pH值变化范围则呈渐趋降低的趋势;随着Na+浓度增加(0~0.6 mol·L~(-1)),落叶生物质炭对3种金属离子所表现的吸附规律各不相同,其中,对Pb~(2+)的吸附量先下降而后渐趋升高,对Cd~(2+)的吸附量逐渐下降,而对Cr~(6+)的吸附量则表现为先增加而后下降。Na+离子浓度由0 mol·L~(-1)提升至0.6 mol·L~(-1)可使生物质炭对Pb~(2+)和Cd~(2+)的吸附量分别降低16.8%和97.1%,相反,对Cr~(6+)吸附量却有所促进,使其增加55.6%;生物质炭对初始质量浓度为400 mg·L~(-1)的Pb~(2+)、Cd~(2+)和Cr~(6+)吸附的数量随接触时间延长(0~1 440min)而逐渐增加,相同条件下由大到小表现为Pb~(2+)、Cr~(6+)、Cd~(2+);生物质炭对Pb~(2+)、Cd~(2+)的吸附主要以电性吸附为主,而专性吸附则为生物质炭吸附Cr~(6+)的主要机制。

Influencing Factors of Pb2+, Cd2+, Cr6+ Ions Adsorbed onto the Biochar Prepared from Populus alba×P.berolinensis and Hosta plantaginea Leaves

The experiment was conducted to discuss the differences and influencing factors of Pb2+, Cd2+, Cr6+ ions of aqueous solution adsorbed onto the biochar prepared from the leaves of Populus alba×P.berolinensis and Hosta plantaginea.The method of limited oxygen pyrolysis was adopted to transform the leaves of Populus alba×P.berolinensis and Hosta plantaginea into the biochar, and then they were served as the adsorbents to adsorb Pb2+, Cd2+, and Cr6+ ions under the different influencing factors containing different initial ion contents, pH, ionic strengths and contact times.With the initial ion concentrations of Pb2+, Cd2+, Cr6+ increasing (0-800mg·L-1), the amounts of Pb2+, Cd2+, Cr6+ ions adsorbed on the biochar prepared from leaves were all enhanced.If the initial ion contents were designed in 0-200mg·L-1, the adsorbed amount of Pb2+, Cd2+, and Cr6+ ion on the biochar would be in descending order of Pb2+>, Cd2+, and Cr6+.However, when the initial ion contents were enhanced to 300-800mg·L-1, their adsorbed amounts showed a descending order of Pb2+, Cr6+, and Cd2+.When the initial pH was increased from 2 to 8, the adsorption rates of Pb2+, Cd2+ on the biochar were significantly promoted, on the contrary, the adsorption rate of Cr6+ had a gradually declining trend in the whole increased process of pH.With the Na+ ion increasing (0-0.6mol·L-1), the biochar had the different adsorbed rules to Pb2+, Cr6+, Cd2+: the amount of Pb2+ being adsorbed on the biochar was declined first and then increased slowly, and in the process the adsorbed amount of Cd2+ was gradually declined, however, the adsorbing capacity of Cr6+ was increased first and then declined.The amounts of Pb2+ and Cd2+ adsorbed on the biochar were reduced by 16.8% and 97.1%, respectively, by enhancing the Na+ ion contents from 0 to 0.6mol·L-1, but in the process the adsorbed amount of Cr6+ was increased by 55.6%.With the extension of contact time, the initial concentrations of Pb2+, Cd2+, Cr6+ ions were 400mg·L-1, whose adsorbed amounts on the biochar had a gradually increasing trend and showed a descending order of Pb2+, Cr6+, and Cd2+.The adsorption of Pb2+ and Cd2+ on the biochar was mostly in the form of electrostatic adsorption, while the specific adsorption was the main way of Cr6+ on the biochar