固定化改性生物质炭模拟吸附水体硝态氮潜力研究

Adsorption of Aqueous Nitrate-N by Immobilized Modified Biochar

为了有效去除水体硝态氮污染,对两种生物质炭(花生壳炭、小麦秸秆炭)进行铁改性处理,研究其对硝态氮吸附特性,考察吸附时间、硝态氮初始浓度、p H、生物质炭添加量和共存离子对改性生物质炭吸附效果的影响。在此基础上,为解决粉末态生物质炭易随水流失的问题,对改性生物质炭进行固定化处理,探索固定化改性生物质炭对硝态氮吸附潜力。研究结果表明,改性生物质炭对硝态氮的吸附主要发生在前6 h,并在24 h左右达到吸附平衡,其吸附量随着水溶液中硝态氮浓度的上升而升高,改性花生壳炭和小麦秸秆炭对硝态氮最大吸附潜力分别为2674、1285 mg N·kg-1,且酸性至中性条件有利于改性生物质炭对硝态氮的吸附。在20 mg·L-1的硝态氮溶液中,改性花生壳炭和小麦秸秆炭的适宜固液比分别为10、28 g·L-1,其去除率达到80%。当包埋载体海藻酸钠浓度为2%、改性生物质炭含量为0.1 g·m L-1时,固定化改性生物质炭微球成形完整,对硝态氮具有较强的吸附能力,固定化并未显著降低改性生物质炭的吸附性能。因此,固定化改性生物质炭能有效吸附水体硝态氮,为污水处理厂尾水等低污染水硝态氮去除提供有效的技术方法。

Adsorption characteristics of nitrate by two common biochars prepared from peanut shell and wheat straw were investigated. Laboratory adsorption experiments were conducted to assess the nitrate-N removal ability of two modified biochars from water at different time,p H, adsorbent dose, nitrate concentration and coexisting ion. To overcome the problem of biochar outflow, methods for immobilizing biochar were also explored. The results showed that nitrate adsorption was very fast within the first 6 hours and then reached equilibrium slowly in24 hours. The adsorption increased with nitrate concentrations. The maximum adsorption amount was 2674 mg N·kg-1and 1285 mg N·kg-1for peanut shell and wheat straw biochars, respectively. The suitable p H for sorption ranged from 3 to 9. The optimal solid-liquid ratios were10 g·L-1and 28 g·L-1for peanut shell and wheat straw biochars, respectively. At 2% alginate and 0.1 g·m L-1biochar, the immobilized biochar microspheres were well-shaped and had a high adsorption capacity for nitrate. Immobilization did not significantly reduce the adsorption capacity of the modified biochars. Therefore, the immobilized modified biochars can be used as effective adsorbents to remove nitrate-N from water including sewage treatment plant effluents.