(中南大學(xué)冶金與環(huán)境學(xué)院，長(zhǎng)沙410083)
摘 要: 從熱力學(xué)分析和試驗(yàn)兩方面研究As(Ⅲ)在酸性水溶液中與金屬鐵的反應(yīng)行為。熱力學(xué)計(jì)算結(jié)果表明：在酸性水溶液中，As(Ⅲ)與金屬鐵作用，分別生成As元素或AsH3氣體的反應(yīng)在熱力學(xué)上均是可行的。試驗(yàn)結(jié)果表明：在溫度為20~80℃、溶液初始pH值為-0.31~4、溶液初始濃度ρ[As(Ⅲ)]為1~20 g/L、鐵粉大量過(guò)剩的條件范圍內(nèi)，由于動(dòng)力學(xué)方面的原因，生成AsH3的反應(yīng)實(shí)際并不會(huì)發(fā)生，鐵粉僅能使As(Ⅲ)還原為As元素。鐵粉“過(guò)量”系數(shù)、溶液pH值和溫度對(duì)沉砷率有顯著影響，提高鐵粉“過(guò)量”系數(shù)和溫度，可使沉砷率增大，在溶液pH值為3的條件下，沉砷效果最佳。在酸性溶液中，鐵粉置換As(Ⅲ)生成As的反應(yīng)難以進(jìn)行到底的原因，可能是由于還原的As在鐵粉表面沉積阻滯了反應(yīng)的延續(xù)。而在初始pH值為3或較高溫度條件下能達(dá)到較高的沉砷率，是由于在這些條件下，置換的砷呈疏散形態(tài)沉積，未能對(duì)鐵粉表面形成緊密包裹，使得反應(yīng)得以延續(xù)。
關(guān)鍵字: As(Ⅲ)；金屬鐵；酸性溶液；反應(yīng)行為
（School of Metallurgy and Environment, Central South University, Changsha 410083, China）
Abstract:The reactive behaviors between As(Ⅲ)and metallic iron in acidic aqueous solutions were investigated thermodynamically and experimentally. The thermodynamic calculation results show that the reactions between As(Ⅲ) and metallic iron in acidic aqueous solutions, which produce both elemental arsenic and AsH3 gas, respectively, are feasible thermodynamically. The experimental results show that, owing to the kinetic reason, the reaction producing AsH3 gas never occurs actually under a wide range of the conditions, such as, temperature from 20 to 80 ℃, initial solution pH value from -0.31 to 4, initial As(Ⅲ) concentration from 1 to 20 g/L, and a massive surplus in iron powders. Under these conditions, the iron powders can only reduce As(Ⅲ) ions from solution as elemental arsenic deposition. These factors, such as surplus coefficient of iron powders, solution pH value and temperature, all have obvious effects on the arsenic deposition rate. The arsenic deposition rate increases with the increase of the surplus coefficient of iron powders and temperature, while the best result of arsenic deposition rate is obtained when the pH value is 3. In acidic aqueous solutions, the reaction of iron powders replacing As(Ⅲ) is difficult to progress quickly to the end, the reason may be that arsenic reduced deposits on the surface of iron powders retard the reaction forward. Moreover, a higher arsenic deposition rate is obtained under the condition of pH=3 or higher temperature, the reason can be deduced that, under these conditions, arsenic deposits in loose form, and does not closely coat the surface of iron powders, thus making the reactions between As(Ⅲ) and iron powders sustainable.
Key words: As(Ⅲ); metallic iron; acidic aqueous solution; reactive behavior
