Adsorption of Nitrite by Hydrochloric Acid Modified Insoluble Dietary Fiber in Watermelon Peel(盐酸改性西瓜皮不溶性膳食纤维对亚硝酸盐的吸附作用)
摘要
Insoluble dietary fiber (IDF) was extracted from watermelon peel and modified by hydrochloric acid. The adsorptions of nitrite by hydrochloric acid modified insoluble dietary fiber (HCl-IDF) and IDF were evaluated. The effects of pH value, oscillating temperature, HCl-IDF dosage, adsorption time, NO-<sub>2</sub> initial concentration on NO-<sub>2</sub> adsorption of HCl-IDF were tested. The results showed that the adsorption capacity of NO-<sub>2</sub> was doubled after modification. When the addition amount of HCl-IDF was 12.5g/L, the removal rate was 64.6% and tended to adsorption equilibrium. When the initial concentration of NO-<sub>2</sub> was 40mg/L, the adsorption was close to saturation. Increasing temperature, lowering pH and prolonging adsorption time were beneficial to the adsorption of NO-<sub>2</sub> by HCl-IDF, and the adsorption equilibrium was reached at pH 1.5,8K and 70min. The adsorption equilibrium of HCl-IDF for NO-<sub>2</sub> could be fitted by Langmuir isotherm equation, and the adsorption kinetics conformed to Langergren quasi-second-order kinetic model, which was mainly chemical adsorption. Thermodynamic studies showed that the adsorption of NO-<sub>2</sub> by HCl-IDF was an endothermic spontaneous reaction.(以西瓜皮为原料提取不溶性膳食纤维(IDF),并通过HCl改性,对比HCl改性西瓜皮不溶性膳食纤维(HCl-IDF)和未改性IDF对亚硝酸盐的吸附作用,探讨pH值、振荡温度、HCl-IDF添加量、吸附时间、NO-<sub>2</sub>初始质量浓度对HCl-IDF吸附NO-<sub>2</sub>的影响。结果表明,经HCl改性后,西瓜皮IDF对NO-<sub>2</sub>的吸附量提升为原来的2倍；当HCl-IDF添加量为12.5g/L时,去除率为64.6%,并趋于吸附平衡；NO-<sub>2</sub>初始质量浓度达到40mg/L时,吸附量接近饱和；升高温度、降低pH值、延长吸附时间有利于HCl-IDF对NO-<sub>2</sub>的吸附,在pH值1.5、温度328K、吸附时间70min时可达吸附平衡；HCl-IDF对NO-<sub>2</sub>的吸附平衡可以通过Langmuir等温方程拟合,吸附动力学行为符合Langergren准二级动力学模型,该吸附过程以化学吸附为主；HCl-IDF对NO-<sub>2</sub>的吸附是一个吸热自发反应。)