Kingston University London, Faculty of Science, Engineering and Computing, Kingston Upon Thames KT1 2EE, UK.
Kingston University London, Faculty of Science, Engineering and Computing, Kingston Upon Thames KT1 2EE, UK.
Sci Total Environ. 2019 Jul 20;675:623-631. doi: 10.1016/j.scitotenv.2019.04.232. Epub 2019 Apr 16.
The removal of phosphorus (P) from sewage effluents is necessary to control eutrophication in receiving waters. Biochar has been proposed and is investigated for the capture and reuse of P, however the forces driving and limiting P adsorption are still largely unclear. To identify the forces governing P uptake by biochar, biochars with markedly different physicochemical characteristics derived from a variety of biomass (oilseed rape straw, wheat straw, miscanthus straw, rice husk, soft wood and sewage sludge residue), pyrolysed at various temperatures, were investigated. The biochar samples were characterised in terms of pH, electrical conductivity, total acidity, carbon chemistry, metal composition, surface area and porosity, and the uptake and release of P was compared to the biochar properties using multivariate analysis. Uptake of P by the biochars as such was low (< 0.71 mg P/g biochar with feed solutions of 50 mg P/l) and, among the variables studied, the biochars' Ca and Mg content was key in P removal and found to be pH dependant. Enhancement of biochar surface area and porosity was carried out by activation with CO at 800 °C and the uptake significantly improved (p < 0.05) (i.e. an increased surface area from <20 m/g up to 781 m/g gave a limited improvement in P removal to <1.2 mg P/g biochar at feed level of 50 mg P/l). These results confirm that the potential to use these unmodified biochars derived from a variety of biomass for P sorption is low, but that the material provides properties that may be modified or enhanced to increase sorption capacity. This study indicates that biochar/biochar feedstock with greater content of Ca and Mg will be more advantageous for P capture.
从污水中去除磷 (P) 对于控制受纳水体的富营养化是必要的。生物炭已被提出并被研究用于捕获和再利用磷，然而，驱动和限制 P 吸附的力在很大程度上仍不清楚。为了确定生物炭对 P 吸收的作用力，研究了源自各种生物质（油菜秸秆、小麦秸秆、芒草秸秆、稻壳、软木和污水污泥残渣）、在不同温度下热解的具有明显不同物理化学特性的生物炭。生物炭样品在 pH 值、电导率、总酸度、碳化学、金属组成、表面积和孔隙率方面进行了表征，并使用多元分析比较了 P 的吸收和释放与生物炭特性的关系。生物炭本身对 P 的吸收很低（<50mg P/L 进料溶液中 0.71mg P/g 生物炭），在所研究的变量中，生物炭的 Ca 和 Mg 含量是去除 P 的关键，且发现其与 pH 值有关。通过在 800°C 下用 CO 进行活化来提高生物炭的表面积和孔隙率，吸收显著提高（p<0.05）（即表面积从<20m/g 增加到 781m/g，在 50mg P/L 的进料水平下，对 P 的去除仅略有提高至<1.2mg P/g 生物炭）。这些结果证实，这些源自各种生物质的未经修饰的生物炭用于 P 吸附的潜力很低，但该材料提供了可以修改或增强以提高吸附能力的特性。本研究表明，含有更多 Ca 和 Mg 的生物炭/生物炭原料将更有利于磷的捕获。
