浊点萃取-双波长光度法测定镀镍废水中的Ni(Ⅱ)

Determination of Nickel(Ⅱ) in Nickel Electroplating Wastewater by Cloud Point Extraction/ Double-Wavelength Spectrophotometry

非离子表面活性剂Triton X-114在温度高于其浊点时形成相分离,利用此行为可浊点萃取富集痕量Ni(Ⅱ)。在pH值为9.5的Na2 B4 O7-NaOH缓冲溶液中,Ni(Ⅱ)与1-(4-硝基苯基)-3-(5,6-二甲基-1,2,4三氮唑)-三氮烯(NPDMTT)反应生成稳定的配位化合物,吸收光谱中475 nm处出现正吸收峰,540 nm处出现负吸收峰,故可采用双波长光度法测定痕量Ni(Ⅱ)。建立了浊点萃取-双波长光度法测定Ni(Ⅱ)的新方法。结果表明:Ni(Ⅱ)含量在0～140μg/L内符合比尔定律,表观摩尔吸光系数为7.29×105 L/(mol.cm);该法用于测定镀镍废水中的痕量Ni(Ⅱ),结果与催化-分光光度法相符,相对标准偏差小于4.0%,加标回收率为98.1%～103.0%。

Non-ionic surfactant Triton X-114 experiences phase separation upon being heated to its cloud point,which makes it feasible to enrich trace nickel(Ⅱ) in nickel electroplating wastewater via cloud-point extraction.Besides,in the Na2B4O7-NaOH buffer solution of pH=9.5,nickel(Ⅱ) reacts with 1-(4-nitrophenyl)-3-(5,6-dimethyl-1,2,4-triazol)-triazene(NPDMTT) to form a stable complex that shows a positive adsorption peak at 475 nm and a negative adsorption peak at 540 nm,which makes it feasible to determine trace nickel(Ⅱ) by double-wavelength spectrophotometry.Therefore,a new cloud point extraction/double-wavelength spectrophotometric method was established to determine trace Ni(Ⅱ) in Ni electroplating wastewater.Results show that Beer's law is obeyed in a concentration range of 0~140 μg/L for nickel(Ⅱ),with the apparent molar absorptivity being 7.29×105 L/(mol·cm).When the established method was applied to determine trace nickel in nickel electroplating wastewater,relevant results agreed well with those of catalytic spectrophotometric method,with the relative standard deviation being less than 4% and the recoveries of samples being within 98.1%~103.0%.