| Fumaric acid is a very important raw material of organic chemistry. During the production process of fumaric acid, lots of wastewater was produced and exhibits low pH, high CODcr value, high thiourea concentration and low biodegradability, therefore, belongs to the system difficult to treat. Some researchers have offered many different methods to treat fumaric acid wastewater, including microelectrolysis of iron and carbon, catalytic microwave oxidation, anaerobic hydrolysis, bio-contact oxidation, supercritical water oxidation and solvent extraction. The disadvantage of all these efficient methods is that fumaric acid is degraded and can not be reused in the processes or the undesirable results. In this article, membrane separation technologies were applied in the recovery and resourceful treatment of fumaric acid wastewater.Firstly, traditional complex extraction was used to treat the fumaric acid wastewater. Trialkylamine N7301, kerosene and n-octanol were selected as the extractant, diluent, and co-solvent, respectively. And the optimum composition of the extraction solvent mixture was 40 vol% N7301+40 vol% kerosene+20 vol% n-octanol. Many influencing factors were investigated in detail, including extractant concentration, feen and stripping characteristics and operating conditions, and the optimum operating conditions were obtained. Furthermore, the heat effect of extraction process, the formation of acid-amine complexes and corresponding equilibrium constant were determined. The reuse times and the loss of the extraction solvent mixture were studied. Under the optimum operating conditions (pH of 0.5, W/O of 1:1, Temperature of 303 K), by complex extraction, fumaric acid was almost completely recovered and the COD of the fumaric acid wastewater decreased from 71040 mg/L to 8411 mg/L, and the COD removal rate came to 88.16%. The regenerated extraction solvent mixture can be resued 7 times without decreasing stripping rate and COD removal rate. The loss of extraction solvent mixture of every extraction process was abou 0.4%.Secondly, hollow fiber supported liquid membrane with stripping dispersion (HFSLM-SD) was introduced to treat fumaric acid wastewater to decrease extraction solvent mixture loss. Polypropylene (PP) as the membrane material, N7301 as the carrier, the Hansen solubility parameters model was introduced to select the suitable liquid membrane organic solvent. Many factors having strong impact on the extraction characteristics of the system were studied in detail, including the characteristics of feed and stripping solutions, the composition of membrane organic phase and the operating conditions (stirring speed, feed and stripping solution pumping velocity, transmembrane pressure and so on). The optimum operating conditions obtained were pH of 1.0 in the feed solution, transmembrane pressure of 7.5 psi, stripping solution of 10% NaOH, stirring rate of 400 rpm and the carrier N7301 concentration of 0.7137 mol/L in kerosene and n-octanol, and the volume ratio of kerosene/n-octanol=7/6. Under the optimum operating condition, the extraction of fumaric acid reached 89.5% and the total TOC removal rate was 96.5%. Fumaric acid crystal was obtained by acidification of the sodium fumarate solution. The kinetics study revealed that the extraction and stripping reactions occurred very quickly. In other words, the overall transport process in the HFSLM-SD was controlled by diffusion in the membrane and the two aqueous boundary layers. After five consecutive transport studies without reimpregnation of the carrier, the extraction remained fairly constant and no significant loss of the membrane solution was observed, which demonstrated that the stability of HFSLM-SD was much remarkable.Based on the optimization of operating conditions and the kinetics and stability studies of HFSLM-SD extraction of fumaric acid, the fumaric acid extraction process by HFSLM-SD was modeled. The fumaric acid, carrier, and extraction complex concentration distributions through HFSLM-SD were obtained by solving the distribution equations model. Many factors influencing the mass transfer of fumaric acid through HFSLM-SD were studied by the total mass transfer coefficient model. Under steady state, the individual mass transfer coefficients of the feed solution, membrane, and the stripping solution were kw =8.044×10-6 m/s, km = 5.333×10-6 m/s, ks = 1.404×10-5 m/s, respectively. The total mass transfer coefficient was Kw = 4.942×10-6 m/s. Operating conditions (feed and stripping pumping velocity, transmembrane pressure, characteristics of feed and stripping solutions and package) had strong impact on distribution ratio, and thus influenced the total mass transfer coefficient.Finally, reverse osmosis was used to further treat fumaric acid wastewater after complex extraction or HFSLM-SD extraction, and the membrane fouling was studied. Furthermore, the combination of complex extraction with reverse osmosis as well as the integration of HFSLM-SD with reverse osmosis was introduced for the recovery and resourceful treatment of the fumaric acid wastewater. Results showed that the TOC of wastewater was below 290 mg/L after treated by the combination technology, and TOC removal rate reached 99.2%. As for the integration technology, the TOC of wastewater was below 100 mg/L, and TOC removal rate was above 99.7%. In conclusion, both the combination of complex extraction with reverse osmosis and the integration of HFSLM-SD with reverse osmosis can effectively recover fumaric acid, and the TOC of the wastewater decreased to further treatment requirement. Therefore, This paper offers an efficient and feasible method for the treatment of industrial fumaric acid wastewater, also for the resourceful treatment of other organic acid wastewater if suitable complex extractant or carrier obtained.
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