摘要
通过静态吸附实验，对比研究了水溶液中硝酸盐在自制层状氢氧化镁铝（每批500kg）（Mg-Al LDH）及其焙烧产物（Mg-Al CLDH）上的吸附性能和机理，用多晶X射线衍射对层状氢氧化镁铝（吸附前后）及其焙烧产物（吸附前后）的结构进行了表征．结果表明，硝酸盐在层状氢氧化镁铝及其焙烧产物上的吸附分别是通过离子交换和“结构记忆”效应实现的．硝酸盐在层状氢氧化镁铝及其焙烧产物上的吸附量受吸附时间、温度、吸附剂用量、初始pH值、溶液初始浓度、离子强度等因素的影响．在25～80℃的条件下，硝酸盐在层状氢氧化镁铝及其焙烧产物上的吸附均符合Freundlich线性吸附等温方程式．在层状氢氧化镁铝上的吸附为放热反应，平衡吸附量为34．87-26．95mg·g^-1，而在焙烧层状氢氧化镁铝上的吸附为吸热反应，平衡吸附量为4541～203.44mg·g^-1,焙烧层状氢氧化镁铝可有效脱除溶液中的硝酸盐，吸附后产物在700℃下重复再生3次，吸附量无变化．溶液初始浓度为500mg·L^-1、吸附剂用量为0．1g、吸附时间为15min、温度为40℃是焙烧层状氢氧化镁铝吸附的最佳条件．
A long consumption of high levels of nitrate can affect health of people, especially infants, causing methaemoglobinaemia or cancer risks due to nitrosamines or nitrosamides. Adsorption of nitrate from aqueous solution by Mg-Al-CO3-layered double hydroxide （Mg-Al LDH） and its calcined product （ Mg-Al CLDH） were compared. Adsorption experiments were carded out as a function of contact time, temperature, adsorbent dosage, initial pH, initial concentration of solution, and ionic strength. The results showed that the adsorption process of nitrate on Mg-Al LDH occurred by ion exchange while on Mg-AI CLDH and the mechanism was a ＇ memory effect＇ , which was corroborated by XRD. In the range of 298 to 353 K, the adsorption data for both sut）strates fit the Freundlich adsorption isotherm equations. The equilibrium adsorption capacity was 34.87 to 26.95 mg·g^-1 for Mg-Al LDH but for Mg-Al CLDH it was 45.41 to 203.44 mg·g^-1.The adsorption process on Mg-Al LDH was found to be exothermic while that on Mg-Al CLDH was endothermic. The results indicated that Mg-Al CLDH was an effective adsorbent for removal of nitrate from aqueous solution and can be regenerated by calcination at 700℃ for 3 h. Orthogonal experiments showed that the initial concentration of solution was the most important factor and the temperature was the next most important factor. The optimum adsorption effect was achieved using the following conditions： adsorption of solution with initial concentration of 500 mg·L^-1 at40℃ for 15 min by0.1 g Mg-Al CLDH.
出处
《环境科学学报》
CAS
CSCD
北大核心
2008年第7期1340-1346,共7页
Acta Scientiae Circumstantiae
基金
国家自然科学基金(No.20477041)资助~~
