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不同磷酸盐改性生物炭对铅的吸附特征研究
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Abstract:
磷改性生物炭对铅有很好的钝化效果，但不同溶解性的磷酸盐改性对铅的吸附效果及影响因素尚不清楚。本研究使用未改性、磷酸二氢钾(可溶)和羟基磷灰石(难溶)改性芦苇秸秆制备生物炭BC、BCK和BCCa，研究了三种生物炭对铅的吸附特征。结果表明，Langmuir模型较好地描述三种生物炭对Pb2+的等温吸附趋势，最大吸附量依次为BC (46.5 mg/g) < BCCa (58.5 mg/g) < BCK (59.5 mg/g)。动力学模型拟合结果表明，三种生物炭对Pb2+的吸附不仅与离子交换等化学过程有关，而且受颗粒内扩散共同作用。此外，BC、BCK和BCCa对Pb2+的吸附能力受溶液pH影响，酸性条件下，pH越低吸附能力越弱。综上所述，磷改性增强生物炭对铅的吸附能力，且随吸附时间和吸附质浓度的增加，吸附容量升高。与不溶性磷酸盐改性生物炭相比，可溶性磷酸盐改性生物炭对铅的吸附效果更佳。
Phosphate-modified biochar is effective in passivating lead, but the effect of biochars modified by phosphates with different solubilities on the adsorption of lead and the impact of pH is unknown. In this study, biochar BC, BCK and BCCa were prepared using unmodified, potassium dihydrogen phosphate (soluble) and hydroxyapatite (insoluble) modified reed straws, investigated the ad-sorption characteristics of the three biochars for lead. The results showed that the sorption iso-therms of Pb2+ were better described using the Langmuir model with the maximum adsorption amounts of BC (46.5 mg/g) < BCCa (58.5 mg/g) < BCK (59.5 mg/g) sequentially. The kinetic models fitting results indicated that the adsorption of Pb2+ by the three biochars was associated with a combination of chemical processes (such as ion exchange) and intraparticle diffusion. Additionally, the adsorption capacities of BC, BCK and BCCa for Pb2+ were affected by solution pH, which was weaker with lower pH under acidic conditions. In summary, phosphorous modification enhanced the adsorption of Pb2+ on biochar; moreover, with the increase of adsorption time and adsorbate concentration, the adsorption amount increases. Soluble phosphate-modified biochar was more effective in Pb2+ adsorption compared to insoluble phosphate-modified biochar.
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