水蒸气蒸馏-离子色谱法测定硫化矿石中氟和氯

对于硫化矿石来说，由于其中含有大量的硫，若采用常规的水蒸气蒸馏，其中的硫会以硫化氢与硫单质的形式馏出，使待测样品净化不彻底。同时，由于蒸馏在硫酸中进行，馏出液会引入一定量的硫酸，当硫酸根浓度过高时，淋洗时间增长，还有碍设备的保养。据此，实验改良了水蒸气蒸馏法，即硫化矿石试样在硫酸中分解，并在160～180 ℃下水蒸气蒸馏，蒸馏过程中加入氧化剂重铬酸钾使负二价硫氧化成硫酸根，以减少馏出液中硫离子的含量，馏出液经D860钡型阳离子交换树脂净化除去硫酸根与铬酸根后，通过离子色谱法测定氟离子与氯离子含量。以4.5 mmol/L NaHCO₃-2.7 mmol/L Na₂CO₃混合溶液为淋洗液，经SH-AG-1保护柱及SH-AC-1分离柱分离，氟离子在0.2～2.0 mg/L、氯离子在0.5～5.0 mg/L范围内与峰面积呈线性关系，相关系数分别为0.999 5和0.999 2。检出限分别为0.006与0.010 mg/L。实验方法用于分析硫化铜精矿样品与硫化锌精矿样品，氟离子和氯离子的加标回收率分别为96.0%～98.0%、96.0%～97.6%之间，相对标准偏差(RSD，n=11)分别为1.3%～3.1%和1.2%～4.0%。

Determination of fluoride and chloride in sulfide ores by steam distillation ion chromatography

Sulfide ores contain high content of sulfur which would be distilled in the form of hydrogen sulfide and elementary sulfur upon conventional steam distillation, rendering an incomplete purification of the to-be-tested sample. Meanwhile, as the distillation process was conducted in sulfuric acid, the distillate would introduce a certain amount of sulfuric acid. Excessive concentration of sulfate radical would increase the leaching time and get in the way of system maintenance. Therefore, the experiment improved the steam distillation method in this way: the sulfide ores samples were decomposed in sulfuric acid and subjected to distillation in steam within the temperature range of 160-180 ℃, with the involvement of potassium bichromate, an oxidant, to oxidize negative bivalent sulfur ion into sulfate radical and reduce the content of sulfur ion in the distillate. The distillate, upon the purification through D860 Barium type cation exchange resin and the removal of its sulfide radical and chromate radical, was subjected to the measurement of the content of fluorine ion and chloride ion by means of ion chromatography. With the mixture solution of 4.5 mmol/L NaHCO₃ and 2.7 mmol/L Na₂CO₃ serving as the eluent, upon the separation through the SH-AG-1 guard column and SH-AC-1 separation column, fluorine ion and chloride ion showed a linear correlation with the peak area within the range of 0.2-2.0 and 0.5-5.0 mg/L with correlation coefficients of 0.999 5 and 0.999 2, respectively. The detection limit was 0.006 and 0.010 mg/L, respectively. The method was applied to the analysis on samples from copper sulfide concentrate and zinc sulfide concentrate, registering an addition standard recovery for fluorine ion and chloride ion at the range of 96.0%-98.0% and 96.0%-97.6%, and a range of relative standard deviation (RSD, n=11) at 1.3%-3.1% and 1.2%-4.0%, respectively.