| Large amount of wastewater from electroplating industry usually contains a variety of toxic organics,among which,nickel is the main component.In recent years,the discharge standard of Ni in China has been increasingly stringent,thus posing new challenges for the advanced treatment of wastewater.The most difficult disposal fraction is the electroless nickel plating wastewater,which contains a wide variety of organic chelating agents.They could remarkably enhance the stability of Ni via complexation,making it difficult to efficiently remove nickel by conventional physicochemical treatment processes including precipitation,adsorption,and ion exchange.The combined process of ozonation coupling physicochemical treatment has been proved to be efficient in destruct Ni-organic complexes,however,its effect on actual wastewater remains to be further verified.In addition,the speciation of Ni have a direct impact on the oxidation process itself and all downstream treatment steps.Hence,it is of great significance to develop a systematic methodology to probe the molecular speciation of Ni-bearing complexes for deep wastewater technology.The aim of this study is to establish a speciation analysis method for nickel in biochemical effluent from electroless nickel plating wastewater by means of HPLCICPMS,HPLC-ESIMS and other analytical methods and to investigate the performance of ozonation-adsorption combined process on Ni-bearing complexes of EN biochemical effluent in a representative electroplating plant.Eventually,the ozonation process parameters and the adsorbent employed in the adsorption process were determined.Meanwhile,this study investigated the regenerative performance and the actual water treatment capacity of selected adsorbent,the ozonation degradation products were also analyzed using the previously established analytical method.The nickel in the biochemical effluent of electroless nickel plating wastewater was dissolved and the large amount of inorganic salts coexisting in the wastewater would interfere with the UV detection of nickel at a wavelength of 395 nm.ICPMS could be used as proprietary detector for 60Ni in electroless nickel plating wastewater.The chromatography hyphenated IC-ICPMS results showed that the nickel in wastewater was composed of positively charged free nickel ions and negatively charged non-free nickel,the specific content of which could be determined by IC-Na-ICP experiment.The molecular formula of nickel-containing complexes could be analyzed by SPE and HPLC-ICPMS-ESIMS experiment.The result demonstrated that the nickel-containing complexes in the biochemical effluent were more hydrophobic with low H/C ratio and high unsaturation,and might contain unsaturated double bond structure or aromatic ring structure which could be effectively degraded by ozone to form hydrophobic degradation products with higher saturation,higher degree of oxidation,smaller molecular size and stronger polarity.Ozonation was necessary for the stable discharge of nickel to the standard,the ozonation-HZO-001 adsorption combined process could reduce the total nickel concentration of electroless nickel plating wastewater to 0.1 mg/L.The working capacity of HZO-001 was around 550 BV,in which HZO-001 could remove all free nickel ions in the ozonation effluent,but had no effect on the nickelcontaining complexes.The sequential recovery experiment showed that HZO-001 nanocomposite had excellent regeneration performance and had great potential in practical applications.This study will be helpful to achieve stable low-level emission of nickel in the electroless plating industry,and provide reference for the construction of speciation analysis methods for other pollutants in industrial wastewater systems. |
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