核桃壳炭的制备及其对氨氮废水的吸附性能研究

为解决当前氨氮废水污染问题,以自制核桃壳炭为吸附剂,以NH+4为模型吸附分子,考察了核桃壳预处理方式、焙烧温度、焙烧时间和铵根离子初始浓度等对氨氮废水吸附的影响,并采用多种手段对核桃壳炭进行表征。研究结果表明:经H3PO4预处理后于700℃焙烧2 h制备的核桃壳炭对低浓度的NH+4具有优异的吸附能力;当铵根离子初始质量浓度为8 mg/L,100 mL NH+4溶液中加入核桃壳炭2 g,吸附时间为240 min时,NH+4去除率达93.41%;核桃壳炭吸附氨氮符合准二级动力学模型。比表面积和孔径分析结果表明:经H3PO4预处理后制备的核桃壳炭的比表面积为269.18 m^2/g,总孔容积为0.1736 cm^3/g,微孔容积为0.125 cm^3/g,平均孔径为5.46 nm。FT-IR、XRD和SEM分析表明:经H3PO4预处理制备的核桃壳炭为石墨碳晶相,表面呈现石墨片层结构,从而使其具有良好的NH+4的吸附性能。

Preparation of Walnut Shell Carbon and Its Adsorption of Ammonia-nitrogen Wastewater

Aiming at the problem of ammonia-nitrogen wastewater pollution, walnut shell carbon was used as adsorbent, and the NH₄⁺ was used as model adsorption molecules. The effects of pretreatment conditions of walnut shell, roasting temperature, roasting time and initial concentration of ammonium ion on the adsorption of ammonia-nitrogen wastewater were investigated. The results showed that walnut shell carbon modified by H₃PO₄ (700℃, 2 h) had excellent adsorption capacity for low concentration NH₄⁺. When the initial concentration of NH₄⁺ was 0.8 mg/L, the amount of walnut shell carbon was 2 g/L and the adsorption time was 240 min, the adsorption rate was 93.41%. Adsorption of ammonium ion by walnut shell charcoal accorded with pseudo-second-order kinetics model. The specific surface area of the walnut shell carbon obtained by H₃PO₄ pretreatment was 269.18 m²/g, the total pore volume was 0.173 6 cm³/g, the micropore volume was 0.125 0 cm³/g and the average pore size was 5-46 nm. Phase characterization of walnut shell charcoal was carried out by infrared (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that walnut shell carbon modified by H₃PO₄ (700℃, 2 h) was graphite-carbon crystalline phase with graphite lamellar structure on its surface which resulted in good adsorption.