Treatment Of Naphthalene-2-ol Production Wastewater With Solvent Extraction-activated Carbon Adsorption Process

With the rapid development of economy in our country, the industry level also gets rapid ascension, and wastewaters from printing and dyeing, paper making,chemical industry, metallurgy, pharmaceutical industries and other industrial production processes also increase. They are all high salt organic wastewaters, which not only contain a large number of soluble inorganic salts such as Na⁺, SO₄^2-, Cl^-, etc.,but also contain degradation-resistant soluble organic matters with high concentration and toxicity. If the aforementioned wastewaters are discharged directly into surface water without any treatment, they will seriously pollute surface water resources, cause severe toxic effects on animals, plants, microorganisms and human, trigger diseases,and even lead death. How to deal with high salt organic wastewaters has become a major research problem in the field of environment. Traditional disposal technologies such as physic-chemical methods or biological methods can not obtain satisfactory treatment results, and these methods always take high processing cost and lead possible secondary pollution. As for high salt organic wastewaters, therefore,developing a way that could efficiently treat such wastewaters will be of great importance to industrial wastewater treatment field, and also provide some relevant bases for the treatment of such wastewaters in the future.This study used the combined solvent extraction and activated carbon adsorption processes to deal with naphthalene-2-ol production wastewater, which was organic wastewater with high salt. The whole process was as follows: the organic matter of high concentration was first separated from wastewater by solvent extraction method.The activated carbon adsorption was then used to further reduce the organic matter in wastewater, as well as possible trace extraction agent dissolving in water, which may lead to higher COD and then using alkali made organics and extractants both recycled and reused by reverse extraction process. At the same time, using chemical method to make activated carbon recycled and reused. The solvent extraction and adsorption processes alternated, and COD content was used as measuring standard of organic matter content in wastewater.This research adopted the combined extraction and adsorption process to deal with wastewater, and the effects of process parameters on solvent extraction and activated carbon adsorption process in treating wastewater were also studied. The experimental results were as follows: As for the solvent extraction process, 1. Theextraction solvent combination of naphthalene-2-ol was TBP + 1-octanol+cyclohexane, and the volume ratio of the three extraction solvents was 20% : 30% :50%. 2. The optimal extraction condition was with the initial pH around 5, three phases, cross-flow extraction volume ratio 1:1 and the reaction time at about 30 min.3. The process was an exothermic process, the extraction temperature was about25 ℃, the stirring speed was at 150 r/min, and under above experiment condition, the removal rate of COD maintained aroud 94% in this process. 4. The reagent that recycle of mixed extractants involved was sodium hydroxide solution with mass fraction of 15%, the experiment conditions of reverse extraction were with O/A ratio1:1 and the contact time of 15 min. Regenerative mixed extractants within 3 cycles could still keep high extraction efficiency. As for the adsorption process: 1. This experiment adopted the natural coconut shell activated carbon as adsorbent. 2. The optimal COD removal efficiency could be obtained when the additive amount of active carbon was 4 g/L and the pH of wastewater was 5, so wasterwater after extraction treatment needed no adjustment. 3. The adsorption ability of activated carbon displayed negative correlation with the temperature. For the sake of economy and convenient operation, the adsorption temperature was set at room temperature about 25℃. 4. This study chose 60 min as the reaction time. 5.Chemical method was used as stripping method of activated carbon in this experiment, using the mass concentration of 10% sodium hydroxide solution, under the condition of 50 ℃. The adsorption ability of activated carbon after regeneration could remain about 84% of the original natural activated carbon. After extraction and adsorption, COD removal rate of wastewater could reach 98%.