不同土壤对化肥厂废水中铵的吸附特征

含铵化肥厂废水污灌有可能引起地下水污染。包气带土壤的吸附作用是阻滞其铵进入含水层的重要过程。选取某包气带不同深度4个典型土样,利用室内批模拟实验,以实验室配制硫酸铵溶液作对比,研究土壤对化肥厂废水中铵的吸附动力学及等温吸附特征。结果显示:土壤颗粒极易吸附铵,废水有机物等物质能延长吸附平衡时间,并影响土壤对铵的吸附能力——在低浓度铵溶液中表现为增加作用,在高浓度铵溶液中的表现为受土壤有机质含量影响;不同质地土壤对铵具有不同的吸附行为,总体上黏性土的吸附能力大于砂土;与Freundlich和Langmuir等温式相比,BET等温式能够与实验吸附数据更好拟合,验证了BET公式用于铵等温吸附特征研究的可行性,表明铵在土壤胶体颗粒中的吸附方式为多分子层吸附。

Adsorption of ammonium in wastewater from fertilizer plant by different kinds of soils

The dischar ge of ammonium2co nt aining w astewater fr om fertilizer plants may cause g ro undwater contamination. T he adsor pt ion by soil in the vadose zo ne is an important pr ocess t o prevent ammonium from entering the aquifer. We select ed four typical so il samples at differ ent depths in a vadose zo ne, and co nducted batch labor ator y experiments to study the adso rption ki2 netics and iso thermal adsor ption char acteristics of the soils w ith reg ard to ammo nium in wastew ater fr om fertilizer plants. T he ammonium sulfat e solution was prepa red fo r the ex periments. Results show ed that ammonium can be adso rbed easily by v arious so il particles. Some materia ls such as o rg anic matters in the wastew ater can pr olong the adso rptio n equilibrium time, and affect the adsor ption capacity of soils to ammo nium; specifically , they will incr ease the capacity in low2concentr atio n ammo nium so lu2 tion, but their effects in hig h2concent ratio n ammonium so lutio n depend o n the soil or ganic matt er co ntent. Soils w ith differ ent textures have differ ent adso rptio n behav iors. Generally , the adsor ption ca pacity o f co hesiv e so il is better than that of sandy soil. Compar ed w ith the Freund lich and L angmuir iso thermal, BET adsorptio n iso thermal can better f it the ex perimental adso rptio n data. This verifies the feasibility of apply ing BET formula to the study of isotherma l adsor ption of ammonium and indicates t hat the adsor ption of ammonium in soil particles is multi2mo lecular layer adso rption.