Study On Process Of Copper-Containing Wastewater By Ion Flotation With Graphene Oxide Based Nano Collector

Copper-containing wastewater is a serious hazard to human health and life.Therefore,how to treat and utilize copper-containing wastewater efficiently and rationally has been one of the hot spots in the field of wastewater treatment.Based on the microstructure and interface characteristics of graphene oxide（GO for short）,the study of Cu（Ⅱ）removal through ion flotation with GO at different oxidation degrees as nano collector was carried out by adjusting the oxidation degree of GO.Subsequently,GO was modified with amidoxime to enhance the selectivity of GO-based nano collector.The main research contents and conclusions were as follows:（1）The influence law of oxidation degree on the microstructure and interface properties of GO nano collectors with four kinds of oxidation degrees were studied in detail.The results showed that with the oxidation degree increased from 18.35%to53.21%,more oxygenous functional groups were inserted into the graphite layers,which increased the spacing between graphite oxide（Gr O for short）from 0.619 nm to0.777 nm,and weakened the attractive force between the layers.Therefore,it was easier to peel off into nano collector with a signle layer or a few layas and a larger lateral size.With the increase of oxidation degree,the oxygenous functional groups introduced onto the surface of GO nano collector increased from 15.805 mmol/g to 32.154 mmol/g,so that the surface hydrophilicity increased and the hydrophobicity decreased and the negative charge density was strengthened.Meanwhile,the surface free energy increased from 60.96 m J/m²to 63.82 m J/m².（2）The influence law and mechanism of GO’s oxidation degree on Cu（Ⅱ）removal and GO’s recycling performance was explored with four oxidation degrees GO as nano collector.The results showed that with the increase of oxidation degree,the adsorption capacity of Cu（Ⅱ）on GO nano collector increased from 72.20 mg/g to 222.57 mg/g,so that the removal of Cu（Ⅱ）increased gradually.Meanwhile,the higher the oxidation degree of GO nano collctor was,the easier it was to complex into flocs with larger particle size,higher compactness and better hydrophobicity,and the probability of collision and adhesion with bubbles would be improved.After flotation,the turbidity of the residual solution decreased from 3.28 NTU to 0.19 NTU rapidly,the recovery rate of water increased from 89.55%to 95.80%,therefore,the enrichment ratio of foam products increased.That was to say,the Cu（Ⅱ）removal performance and flotation efficiency of GO nano collector increased with the increase of its oxidation degree.In addition,GO nano collector with four oxidation degrees all possessed good recycling performance,and the higher the oxidation degree,the better recycling performance.（3）The selective adsorption experiment of multi-component metal ions on GO nano collector was carried out,and the influence law and mechanism of oxidation degree on the selective performance of GO nano-collector were systematically studied.The results showed that the selective order of GO nano-collector for multi-component heavy metal ions was Cu（Ⅱ）>Cd（Ⅱ）>Ni（Ⅱ）>Zn（Ⅱ）>Co（Ⅱ）.But the maximum selcectivity coefficients（βCu（Ⅱ）/Co（Ⅱ）、βCu（Ⅱ）/Ni（Ⅱ）、βCu（Ⅱ）/Zn（Ⅱ）和βCu（Ⅱ）/Cd（Ⅱ））of GO nano collector were 18.969,11.880,18.182 and 8.106,respectively,so that the selectivity performances were poor,which needed to be improved urgently.In addition,the selectivity of GO nano collector for Cu（Ⅱ）became worse with the increase of oxidation.（4）Oxime ammonia functionalized GO nano collector（AMID-GO for short）was synthesized by modifying GO with 1,3-diamino-1,2,3-trioxime propane（AMID for short）,and its selectivity performance and mechanism were studied in detail.The results showed that the selectivity coefficients of AMID-GO(β_{Cu（Ⅱ）/Co（Ⅱ）}、β_{Cu（Ⅱ）/Ni（Ⅱ）}、β_{Cu（Ⅱ）/Zn（Ⅱ）}和β_{Cu（Ⅱ）/Cd（Ⅱ）})were 3.23,7.56,3.67 and 3.06 times that of GO3,respectively.The selectivity for Cu（Ⅱ）had been greatly improved.During the interaction between AMID GO and Cu（Ⅱ）,both O in oxime group and N in adjacent oxime group participated in the adsorption of Cu（Ⅱ）through complexation,making the stability energy of the complex formed by AMID-GO and Cu（Ⅱ）much higher than the complex formed by AMID and other co-existing ions.Therefore,AMID-GO nano collector exhibited a high selectivity for Cu（Ⅱ）in the ion flotation process.（5）GO3,AMID-GO and sodium dodecyl sulfate（SDS for short）were used to purify simulated electroplating wastewater by ion flotation.The results showed that after process optimization,the wastewater treated by the three kinds of collectors could meet the electroplating wastewater discharge standard（GB21900-2008）and the first-level emission standards for the second category of pollutants（GB8978-1996）.By comparison,it was found that nano-collector had the advantages of low dosage,good removal performance,high enrichment ratio of foam products,short process,etc.,and AMID-GO could also recover useful components during the treatment of copper-containing wastewater with high selectivity,so as to realize resource recycling and provide a solid foundation for the practical application of nano-collector ion flotation for copper-containing wastewater purification.