碱高温熔融-乙二胺四乙酸滴定法测定铝灰中的总铝量

Determination of Total Aluminum in Aluminum Ash by Ethylenediaminetetraacetic Acid Titration with Alkali High-Temperature Melting

为了加强对铝灰中铝资源的回收利用,提出了碱高温熔融-乙二胺四乙酸(EDTA)滴定法测定铝灰中总铝量的方法。针对铝灰基质复杂以及钙、镁、氩含量高的特点,优化了前处理和滴定条件。0.1 g样品经干燥、乙醇润湿后,加入3 g氢氧化钠和2 g磷酸钠(与钙、镁形成沉淀分离除去,避免钙、镁氢氧化物吸附Al^(3+)),于400℃预熔融20 min。加入1 g过氧化钠,于750℃熔融15 min。加入沸水煮沸,使熔块全部溶解,再加入3 mL 6 mol·L^(-1)盐酸溶液煮沸除去过氧化氢。用水定容至100 mL,过滤,取滤液25 mL,加入10 mL 6 mol·L^(-1)盐酸溶液和5 mL高氯酸,加热至近干,以消除样品中高含量F^(-)对Al^(3+)的络合干扰。残渣用10 mL 6 mol·L^(-1)盐酸溶液溶解,再加入10 mL水、8 mL 40 g·L^(-1)EDTA溶液和二甲酚橙指示剂,用6 mol·L^(-1)盐酸溶液将溶液调至亮黄色,煮沸5 min,使EDTA充分络合Al^(3+)。加入15 mL乙酸-乙酸钠缓冲溶液(pH 5.8)和二甲酚橙指示剂,用1.00 mg·L^(-1)锌标准溶液将溶液滴定至橙红色。加入5 mL氟化钾溶液(100 g·L^(-1)),煮沸5 min,将Al^(3+)从EDTA络合物中完全置换出来。加入10 mL乙酸-乙酸钠缓冲溶液(pH 5.8)和二甲酚橙指示剂,用1.00 mg·L^(-1)锌标准溶液将溶液滴定至橙红色,记录滴定液消耗体积,并通过滴定度计算总铝量。结果显示:总铝回收率为96.8%~103%,测定值的相对标准偏差(n=6)小于1.0%,方法适用于试验条件有限的实验室进行矿山冶炼铝灰中总铝量的测定。

In order to strengthen the recycling and utilization of aluminum resources in aluminum ash,the method was proposed to determine the total aluminum in aluminum ash by ethylenediaminetetraacetic acid(EDTA)titration with alkali high-temperature melting.In response to the complexity of the aluminum ash matrix and the high content of calcium,magnesium,and fluorine,the pre-treatment and titration conditions were optimized.After drying and wetting with ethanol,0.1 g of the sample was taken,3 g of sodium hydroxide and 2 g of sodium phosphate were added(forming precipitates with calcium and magnesium and separating them out,to prevent calcium and magnesium hydroxides from adsorbing Al^(3+)),and the mixture was pre-melted at 400℃for 20 min.Then 1g of sodium peroxide was added,and the mixture was melted at 750℃for 15 min.Boiling water was added to dissolve all the frits by boiling,and 3 mL of 6 mol·L^(-1)hydrochloric acid solution was added.The mixed solution was boiled to remove hydrogen peroxide.After diluting to 100 mL by water and filtering,25 mL of the filtrate was taken,mixed with 10 mL of 6 mol·L^(-1)hydrochloric acid solution and 5 mL of perchloric acid,and the mixed solution was heated to near dryness to eliminate the complexation interference of F^(-)with high content in the sample on Al^(3+).The residue was dissolved by 10 mL of 6 mol·L^(-1)hydrochloric acid solution,and 10 mL of water,8 mL of 40 g·L^(-1)EDTA solution,and xylene orange indicator were added.The solution obtained was adjusted to bright yellow color by 6 mol·L^(-1)hydrochloric acid solution,and boiled for 5 min,allowing EDTA to fully chelate Al^(3+).Then 15 mL of acetic acid-sodium acetate buffer solution(pH 5.8)and xylenol orange indicator were added,and 1000 mg·L^(-1)zinc standard solution was added for titration until the solution turned orange red.Then 5 mL of potassium fluoride solution(100 g·L^(-1))was added,and the mixed solution was boiled for 5 min,to completely replace the Al^(3+)from EDTA complex.After adding 10 mL of acetic acid-sodium acetate buffer solution(pH 5.8)and xylenol orange indicator,titration was conducted with 1000 mg·L^(-1)zinc standard solution until the solution turned orange red,and the volume of titrant consumed was recorded.Total aluminum was calculate by titration.It was shown that the total aluminum recoveries were found in the range of 96.8%-103%,and RSDs(n=6)of the determined values was less than 1.0%.The proposed method was suitable for the determination of total aluminum in aluminum ash from mining smelting in laboratories with limited experimental conditions.