| With the speeding up of industrialization process, the heavy metal wastewaterpollution of the environment by increasingly serious, has been a serious threat tohuman health. Iron and steel metallurgy enterprises water consumption is very big,and they are the kind of enterprises with a lot of heavy metal wastewater discharge.Heavy metal wastewater treated with traditional chemical method is often not up tothe standard, treated wastewater contains a large number of Cl-, SO42-and Na+whichcan improve the water conductivity and be harm to aquatic environment. Membraneseparation technology is one of the high and new technologies which can be appliedto water treatment, its main advantage is that without adding medicament, clean andhigh efficiency, simple process flow, and through the multi-stage membraneprocessing, the valuable resources contained in wastewater can be recycled andproduced water also can be recycled. This paper mainly studies on the separations ofhigh salinity wastewater and high concentration acid metallurgy heavy metalwastewater using nanofiltration membrane (NF) and reverse osmosis membrane (RO).Use a high concentration sodium chloride solution and sodium sulfate solution asthe high salt waste water to study the effect of NF/RO membrane intercept andinfluence factors. The results show that the two kinds of membrane separationtechnology are greatly influenced by the pH of the raw water. The stronger the acidwastewater is, the lower intercept rate of the membrane has. But with the alkalineconditions, the membrane intercept rate of salt is maintained at a good level. As theoperating pressure change, the penetrating fluid pressure changes at the same time,but the overall driving force maintains a constant, membrane intercept rate were notsignificantly affect. NF/RO membrane to the interception of sodium sulfate is superiorto intercept of sodium chloride. NF membrane main intercepts sodium sulfate,entrapment of sodium chloride is only20%~30%. The interception rate of sodiumsulfate and sodium chloride by RO membrane is much higher than NF membrane.Study on the acid high concentration heavy metal wastewater containingchromium, lead, copper, zinc treatment using NF-RO membrane and study themembrane interception rate of the metal ions and the influencing factors of membraneinterception rate. Results show that the NF/RO membrane interception rate of metalion is slightly decreased with the increase of metal ion concentration. High concentration wastewater (each metal ion concentration in the range of50~100mg/L)after NF membrane treatment, the metal ion concentration in penetrant reduced to therange of10~30mg/L. Put the kind of waste water which in the scope of theconcentration into the RO membrane as depth processing. the results show that eventhe concentrations of Cr3+, Pb2+, Cu2+, Zn2+are as high as30mg/L, RO membranehas good effect of entrapment on its, interception rate were99.8%,97.0%,97.8%and99.8%respectively. RO membrane fresh water, in addition to the concentration ofCu2+only reaches the secondary indexes of the national integrated wastewaterdischarge standard GB8978-1996, the other three kinds of heavy metal ionsconcentration reaches the first index requirements.The study found that RO membrane interception rate of metal ions is not only bythe affects of metal ion valence, ionic radius, hydrated radius, also is associated withthe apparent concentration of ions in the water. Membrane interception rate of highmetal ion valence is higher than the low ones. When the ion concentration is in a lowlevel, ionic radius is the main influencing factor of the membrane intercept rate. Whenion concentration is in a higher level, the ion hydration radius is the main influencingfactor of the intercept rate. When the ion concentration is in the medium level, themembrane interception rate is affected by ionic radius and the ion hydration radiustogether. |
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