不同类型土壤中As(V)解吸行为的研究

The arsenate adsorption behavior of seven Chinese soils

为了解As(V)在土壤中的解吸行为及不同类型试剂(NaOH、NaCl、NaHCO3、柠檬酸、草酸及磷酸盐缓冲液)对所吸附砷的解吸效果,对As(V)在不同类型土壤中的解吸热力学和动力学效果进行了研究.结果表明,NaOH和磷酸盐缓冲液对几种土壤吸附砷的解吸效果较好,解吸率分别在47.3%～73.0%和35.4%～66.6%之间;除黑土外,草酸和柠檬酸对其它几种土壤吸附砷的解吸能力中等;NaHCO3和NaCl对各种土壤吸附砷的解吸效果较差,解吸率分别在10.3%～42.1%和2.3%～32.2%之间.供试土壤中,第四纪红色粘土发育的红壤和花岗岩发育的红壤解吸的砷量较高,解吸量分别在0.004～0.135mg·g-1和0.009～0.101mg·g-1之间,黄壤和黑土其次,紫色土、紫色砂页岩发育的红壤和潮褐土的解吸量较少,潮褐土的解吸量仅在0.012～0.027mg·g-1间.以NaOH为解吸剂进行热力学试验发现,随初始砷浓度的增加,土壤对砷的吸附量和解吸量均相应增加,吸附量与解吸量间呈线性关系;动力学试验结果表明,几种土壤的解吸量均在开始的1h内快速上升,5min内即达到平衡解吸量的43.9%～65.1%,至2h后基本处于稳定状态,此时解吸量达平衡解吸量的78.4%～91.8%,之后解吸量和解吸率均不再变化或变化很小.

Arsenate desorption was studied in batch experiments using seven Chinese soils and different extractants（sodium hydroxide,sodium chloride,sodium bicarbonate,citric acid,oxalic acid and phosphate buffer solution）.The results showed that NaOH and phosphate buffer solutions were most effective to extract As（V） from soils,removing 47.3%~73.0% and 35.4%~66.6% of As（V）,respectively.Except for black soil,the extractability of the citric acid and oxalic acid solutions were moderate.For the solutions of NaHCO3 and NaCl,only 10.3%~42.1% and 2.3%~32.2% of As（V） were extracted,respectively.Among the seven soils,As（V） desorbed from red soil developed from Quaternary red clay soil and red soil developed from granite were the highest,with desorbed amounts of 0.004~0.135 mg · g-1 and 0.009~0.101 mg · g-1,respectively,followed by yellow soil and black soil.The amounts of As（V） adsorbed on purple soil,red soil developed from purple sandy shale and fluvo-aquic soil were released less,especially on fluvo-aquic soil,with a desorbed amount of 0.012~0.027 mg · g-1.The results of isotherm experiments with NaOH as an extractant showed that the adsorption and desorption amounts of As（V） on different soils increased with the increase of initial As（V） concentration,and a significant positive relationship was found between adsorption and desorption amounts.With time,As（V） on the soils desorbed rapidly within 1 h,reaching 43.9%~65.1% of the desorption equilibrium within 5 minutes.After 2 h,the desorption curves changed slightly,reaching 78.4%~91.8% of the equilibrium desorption amount.