纳米羟基磷灰石对土壤重金属吸附与解吸特性的影响

采用纳米羟基磷灰石(nano-HAP)对安吉(AS)和华家池(HS)的土壤进行重金属吸附-解吸实验.结果表明,土壤对重金属的吸附均可用Langmuir方程描述,重金属在土壤中的亲和力顺序:Pb(Ⅱ)Cu(Ⅱ)Cd(Ⅱ)Zn(Ⅱ).AS的pH值、土壤有机质(OM)含量和阳离子交换量(CEC)均高于HS,因此具有更强的吸附性能.nanoHAP的施加显著增加了土壤对重金属的吸附量和吸附亲和力,nano-HAP添加量为3%时,AS和HS的KCu值分别从0.979 1和0.284 9提高至1.389 7和1.131 6,KPb值分别从0.566 8和0.234 3增加到1.963 4和3.442 7,KCd值分别从0.420 8和0.096 8增加至1.724 3和0.426 9,KZn值分别从0.313 4和0.015 1增加0.508 7和0.099 7.nano-HAP对pH值较低和OM、CEC含量较低的土壤具有更显著的吸附改良作用.同时,nano-HAP的施加能有效降低土壤重金属的解吸百分数,表明nano-HAP可以显著削弱重金属的移动性,增加其在重金属污染土壤中的化学稳定性.

Effect of nanoscale hydroxyapatite on soil adsorption and desorption of heavy metals

Adsorption and desorption of Cu(II), Pb(II), Cd(II) and Zn(II) on the soil of Anji (AS) and Huajiachi (HS) amended with nanoscale hydroxyapatite (nano HAP) are studied by batch experiments. The result shows that Langmuir model fits the experimental data very well with high coefficients (R2=0.95~0.99). The adsorption isotherms show that different kinds of heavy metals have different affinity to the soils following the orders of Pb(II)>Cu(II)>Cd(II)>Zn(II). The amount of each heavy metal adsorbed on AS soil is higher than that on HS soil, because the former has higher pH、OM and CEC values than the latter. The amendment of nano HAP in the soils significantly can enhance the adsorption ability of heavy metals. The values, simulated from the adsorption isotherms, increased from 0.979 1 to 1.389 7 for Cu(II), 0.566 8 to 1.963 4 for Pb(II), 0.420 8 to 1.724 3 for Cd(II), 0.313 4 to 0.508 7 for Zn(II) on AS, and from 0.284 9 to 1.131 6 for Cu(II), 0.234 3 to 3.442 7 for Pb(II), 0.096 8 to 0.426 9 for Cd(II), 0.015 1 to 0.099 7 for Zn(II) on HS, when 3% nano HAP is added into the soils. Nano HAP is more efficient to soils which has low pH、OM and CEC values. The nano HAP has remarkably inhibited the desorption of heavy metals from the soils, suggesting that the addition of nano-HAP can significantly reduce the mobilization of heavy metals and increase their geochemical stability in metal contaminated soils.