几种不同处理方法对活性炭表面化学性质的影响

活性炭表面官能团的种类和数量决定了活性炭的表面化学性质,而化学性质决定了活性炭的表面吸附特性。使用5种常见的处理方法处理活性炭,采用Boehm滴定法,XPS对活性炭进行表征,通过单因素实验系统地考察了活性炭表面含氧官能团及碱度随处理条件的变化,同时通过碱度变化讨论了部分处理方法对于原活性炭表面灰分的去除。结果表明:在处理液150 mL、20℃、200 r/min条件下:50 g活性炭经0.01～5 mol/L HCl处理4 h,活性炭表面碱度降低范围63.2%～76.5%,灰分去除效果好,低浓度的盐酸就能达到较好的灰分去除效果,活性炭表面没有形成大量的含氧官能团;在HNO3浓度1～12 mol/L、处理时间1～8 h、活性炭量25～75 g条件下处理后总碱度降低显著,灰分去除效果优于HCl处理,HNO3氧化作用使活性炭表面形成了大量含氧官能团,总酸度、羧基、内酯基、酚羟基含量均相对于原活性炭增加明显;在H2O2质量浓度5%～20%、处理时间0.5～4 h、活性炭量25～75 g条件下处理后碱性灰分去除不好,活性炭表面没有形成大量含氧官能团,H2O2处理引起活性炭表面化学性质变化较小;在NaOH浓度0.1～2 mol/L、处理时间1～8 h、活性炭量25～75 g条件下处理后碱度增加明显,酸度减小明显,羧基、酚羟基含量降低。50 g活性炭在微波功率100～500 W、处理时间2～10 min、载气流量600～1 400 mL/min条件下经微波处理后,微波热效应导致含氧官能团分解,总碱度增加,总酸度下降,羧基含量、内酯基含量降低,酚羟基含量因条件的不同而变现出不同的变化。

Effect of several different treatment methods on surface chemical properties of actived carbon

The surface chemical properties of activated carbon(AC),which were marked by the types and quantities of function groups on the surface,determine the absorption properties of AC.Five common surface treatment methods were used in treatment of AC.Boehm titration,XPS and other analysis methods were applied to characterize AC.Changes of oxygen-containing functional groups and alkalinity on AC vary with different treatment conditions were investigated through single-factor experiment,as well as the effect of some treatments on the removal of ash was also investigated.The results showed that alkalinity dcreased in range of 63.2%～76.5%,the removal efficiency of ash was well,but there was not many chemical propertities formed when AC(50 g) was treated by 0.01～5 mol/L HCl for 4 h.The alkalinity dcreased obviorsly,the removal efficiency of ash was better than HCl treatment and a lot of chemical propertities formed when the AC was treated by HNO3 under the conditions of HNO3 concentration of 1～12 mol/L,treatment time of 1～8 h,AC mass of 25～75 g,the acdity,the contents of carboxyl,hydroxyl and lactone increased evidently.The removal efficiency of ash was bad and there was not many chemical propertities formed when AC was treated by H2O2 under the conditions of H2O2 mass concentration of 5%～20%,theatment time of 0.5～4 h,AC mass of 25～75 g.The alkalinity increased obviorsly and the acidity decreased obviorsly when AC was treated by NaOH under the conditions of NaOH concentration of 0.1～2 mol/L,treatment time of 1～8 h,AC mass of 25～75 g,the contents of carboxyl and hydroxyl dcreased.The haeting effect of microwave caused the oxygen propertities decomposed,the alkalinity increased,the acdity increased and the contents of carboxyl and hydroxyl decreased when AC was treated by microwave under the conditions of microwave powder of 100～500 W,treatment time of 2～10 min,gas flow of 600～1 400 mL/min,the content of lactone changed differently with different conditions.