粉煤灰对水溶液中磷的吸附性能及机理

以粉煤灰为吸附剂去除溶液中的磷,考察了其吸附除P动力学特征、热力学特征以及溶液初始pH和粉煤灰投加量对吸附除P效果的影响,并对其吸附除P机理做了初步探讨。结果表明,在给定实验条件下,粉煤灰对P具有较好的去除效果,随着初始P浓度从10 mg/L升高到80 mg/L,平衡吸附量为0.46～2.44 mg P/g粉煤灰,吸附效率从92.2%降低至61.1%;对不同浓度的含P溶液,粉煤灰最适用量为0.6～1.5 g粉煤灰/mg P;相同反应条件下,当温度由25℃升高到45℃时,P初始吸附速率提高了3倍;粉煤灰对P的吸附过程能够较好地拟合Langmuir、Freundlich及D-R吸附等温模型,相关系数均在0.98以上。通过对吸附饱和的粉煤灰进行解析实验发现,初始P浓度较低(<50 mg/L)时,以化学吸附为主,而在初始P浓度较高(>80 mg/L)时,则以物理吸附为主。

Performance and mechanism of phosphorus adsorption in aqueous solution with fly ash

Fly ash was used as adsorbent to remove P from solution,phosphorus adsorption kinetics,thermodynamics as well as the influences of pH and adsorbent dosage on P removal effects were all investigated,the mechanism of P adsorption onto fly ash was preliminarily studied.Results indicated that P could be removed by fly ash efficiently under the given conditions.With the concentration of P increased from 10 mg/L to 80 mg/L,the equilibrium adsorption capacity of fly ash increased from 0.46 mg P/g fly ash to 2.44 mg P/g fly ash,while the removal efficiency decreased from 92.2% to 61.1%.The optimal dosage of fly ash was 0.6～1.5 g fly ash/mg P,even when P concentrations were different;under the same conditions,the initial sorption rate was improved by 3 times when the temperature increased from 25℃ to 45℃.Langmuir,Freundlich and D-R isotherms were all fit to the adsorption characteristics of fly ash(R2>0.98).The results obtained from P desorption indicated that with lower P concentration(<50 mg/L),the adsorption was mainly chemical reaction,whereas,with higher P concentration(>80 mg/L),physical adsorption was the main process.