纳米羟基磷灰石改性生物炭对铜的吸附性能研究

Comparison of copper adsorption onto unmodified and nano-hydroxyapatite-modified wheat straw biochar

为了提高生物炭对重金属铜的吸附能力,选取小麦秸秆作为原料,将不同比例纳米羟基磷灰石与秸秆混合均匀,在600℃高温限氧条件下制备了羟基磷灰石改性生物炭材料,比较了生物炭和生物炭改性材料对铜的吸附特性,同时分析了两者间的表面特征等。结果表明:热重分析显示,生物炭表面附着纳米羟基磷灰石可以提高生物炭的热稳定性;扫描电子显微镜分析显示,纳米羟基磷灰石可以较为均匀地附着在生物炭表面,但同时会伴随不同程度的聚集现象;接触角测试结果显示,生物炭表面附着纳米羟基磷灰石可降低其疏水性;生物炭和生物炭改性材料对铜的吸附符合伪二级动力学模型,生物炭改性材料可使铜的吸附速率提高7.69%~130.77%;生物炭和生物炭改性材料对不同浓度的铜吸附符合Langmuir等温吸附模型,对铜的最大吸附量分别为32.65 mg·g^(-1)和57.01 mg·g^(-1)。

To improve wheat straw biochar′s removal ability of copper from polluted water and soils, wheat straw biochar was modified using nano-hydroxyapatite. The characteristics of unmodified and nano-hydroxyapatite-modified wheat straw biochars were analyzed, and batch and kinetic adsorption experiments were conducted. The results showed that the nano-hydroxyapatite coating was uniformly attached to the surface and improved the thermal stability of the wheat straw biochar. All three concentrations of the nano-hydroxyapatite coating decreased the hydrophobicity of the biochar. The nano-hydroxyapatite coating increased the adsorption rate of copper by 7.69%~130.77%. The maxi-mum adsorption capacity of nano-hydroxyapatite-modified wheat straw biochar increased from 32.65 mg·g^-1without coating to 57.01 mg·g^-1with 0.5% coating. Copper adsorption onto unmodified and nano-hydroxyapatite-modified wheat straw biochars were well fitted by the pseudo-second-order kinetics and Langmuir adsorption models.