Experimental Study On Reducting Of Salt In 2,4-D Acid Production Wastewater By Ion Exchange Method

2,4-dichlorophenoxy acetic acid is not only a highly efficient hormone used in plant growth, but also a kind of broad-spectrum herbicide, which is widely used in recent years. But acid precipitation liquor is organic wastewater with high salinity and high concentrations which is difficult to treat.In this study, before neutralization process and acid precipitation process, ion exchange method was used to transfer Na+ in acid precipitation liquor exchanged with H+ in chloroacetic acid. Firstly, chloroacetic acid solution flew through the Na resin, then Na resin was converted into H resin, which decreased the amount of alkali in neutralization process. Analog condensation liquor flew through the H resin, then H resin was converted into Na resin, which reduced its' pH and decreased the amount of acid used in acidification process. This process decreased the amount of acid and alkali as well as the salt content in acidulated wastewater.Firstly, by comparing exchange capacity in exchange volume and balance time of three resins'(732?D001?110), which used diluted concentration simulated solution, the resin with best exchange capacity was chose. Optimal experiments conditions under diluted concentration simulated solution were studied. Finally, repeated stabled experiments under both dilute concentration simulated solution and concentrated solution was studied to test the durability of the resin.Three kinds of exchange resins' dynamics experimental data concluded by using dilute concentration simulated solution showed that Na resins and H resins' balance times were all 20 minute at the temperature 293K, their equilibrium adsorption arranged order of size is D001>732>110. Weber-Morris model showed that both the particle diffusion and liquid film diffusion were the rate-controlling step of adsorption. The adsorption isotherm equilibrium experiments demonstrated that the equilibrium adsorption capacity decreased with the temperature increasing. The adsorption isotherm data could be well fitted with the Langmuir isotherm equation, it showed that when at the temperature 293 K and the flow rate 8 BV/h, the order of three kind of resins'exchange capacity is D001>732>110, and the resins'adsorption capacity of Na+ was greater than H+. According to the fitted results of Freundlich isotherm equationof Na-resins'data, raise temperature was not conducive to adsorption, and n>2 showed a preferential adsorption. According to H-resins'data fitted by Redlich-Peterson isotherm equation. Krp decreased with temperature increasing, which also showed that raising temperature was not conducive to the adsorption. The thermodynamic data (? G<0,? H<0, ? S<0) showed that reaction of Na-resins converted to H and H-resins converted to Na were all spontaneous and exothermic reactions along with a increase of the system entropy.Results of column optimization experiments verified results of static absorption experiments:adsorption capacity of three resins decreased with the increasing of temperature. After changing the experimental conditions of different flow velocity, get optimum operating conditions that temperature was 293 K, flow velocity of chloroacetic acid solution was 4BV/h, flow velocity of saturated simulated solution was 5BV/h.Repeated stabled experiments under concentrated solution showed that after the analog feed concentration increasing, the exchange capacity of the resin was improved. It might be because Na-exchange experiments process under high alkalinity concentrated solution hadn't generated 2,4-dichlorophenoxy acetic, and H-exchange experiments process under concentrated solution exchanged completely. Therefore, exchange efficiency of stability experiments under high concentration solution was better than low concentration.Based on the calculationdata of acid andalkali consumptionsavings, the relationship between savings and volume of effluent were achieved. In effluent of H-exchange experiment, the first 20 mL (0.952BV) saved alkaline 62.61%. When effluent reached 60 mL (2.86BV), resin was saturated. At the same time, Cumulative alkaline saving was 28.45%. In effluent of Na-exchange experiment, the first 15 mL (0.714BV) saved alkaline 50.34%. When effluent reached 40 mL (1.90BV), resin was saturated. At the same time, cumulative alkaline saving was 23.23%. Data above can be used as the basis of practical technology design.In a word,2,4-D's production process improved by ion exchange method could reduce the amount of acid and alkali, and made Na+ be reused to decrease Na+ in acidic waste water. Therefore, it decreases the difficult of wastewater treatment and save the cost of wastewater treatment and production.