超声波辅助微波消解预处理测量污泥金属元素

Measuring Metal Elements in Sludge with Ultrasound-assisted Microwave Digestion Pretreatment

以实验室污泥和污水厂污泥为研究对象,建立了超声波辅助微波消解预处理测量污泥金属元素的方法与程序。首先通过超声波分散污泥絮体,然后对污泥进行加热预处理和微波消除,最后采用火焰原子吸收法测量污泥中的金属元素。结果表明,150 W超声波作用于25 mL污泥3 min为超声波分散污泥的较优条件,能保证后续操作过程取样均匀。微波消解前适宜的加热预处理条件为90℃,20 min。实验室污泥微波消解的较优酸体系为2 mL双氧水＋4 mL反王水（或4 mL王水）;污水厂污泥微波消解的较优酸体系为1 mL氢氟酸＋2 mL双氧水＋4 mL王水,同时,第3阶段消解条件为压强2.0 MPa下消解20 min。超声波辅助微波消解预处理具有用酸量少、简易快捷、准确度和精密度高等优点,测量K,Ca,Mg,Fe的相对标准偏差≤2.75%,加标回收率为97.5%～102%。

By adopting laboratory sludge and sewage sludge as objects, a method and process of measuring metal elements with ultrasound-assisted microwave digestion pretreatment is researched. First, sludge flocs are dispered by ultrasound. Then they are pretreated by heat and disgested. Last mental elemeats are measured by using atomic absorption. The results show that the optimal conditions of ultrasonic treatment are 150 W in 3 min for 25 mL sludge, which can ensure well-distributed sampling in the following procedure. Before microwave digestion, the suitable condition of heating pretreatment is 20 min at 90 ℃, the optimal acid of microwave digestion for laboratory sludge is 2 mL hydrogen peroxide with 4 mL anti aqua regia（or 4 mL aqua regia）, while the optimal acid system of microwave digestion for actual sewage sludge is 1 mL hydrofluoric acid, 2 mL hydrogen peroxide and 4 mL aqua regia, of which the third digestion procedure is 20 min at 2.0 MPa. Ultrasound-assisted microwave digestion pretreatment has some advantages, such as saving acid, simplicity, high precision and accuracy, with which the relative standard deviation of measuring K, Ca, Mg, Fe in sludge is lower than 2.75%, and the recovery is 97.5%-102%.