The Study Of Desalination Technics Of Fruit Acid Effluent

In international market, the price of apple juice concentrate is in direct proportion with its acidity. If the acidity rises by 1°,the price will increase $100-150 /t. Most apple juice concentrate in China are low-acidity juice as a result of apple material. While, in the production of color and acid free apple juice, a great deal of natural L-malic acid is let with resin alkali lotion. That is a waste of resources, but also brings about environment pollution. In this paper, the feasibility of three methods(electrodialysis,ion exchange resin and TiO2 alloy membrane) used in desalination and reutilization of fruit acid effluent was studied. Their technical parameters were as follows:1. The optimum technological conditions of desalinating by electrodialysis were found out. Under the condition of pH4.0 , electric current 11A ,flow rate of effluent 9cm/s and 2 hours'circulation, the desalination rate reached more than 99%. Na+ in the effluent could be desalted to 42.88 mg/L, and the L-malic acid in the effluent reduced by 18.94%.Expierance model of limited electric current density used for this equipment is: Jlim=87.272×c0.749v0.854.2. The gel acid cinnamene resin of HP1110Na was selected as the best desalination resin. The optimal desalinating process based on the following condition: desalination was optimized at effluent pH 4.0, flow volume 4 BV/h. Under these conditions, the volume ratio of resin and effluent in which the concentration of Na+was less than 30mg/L was about 1:6,and the loss rate of malic acid was 18.94%.The optimum regenerative solution was the solution of hydrochloric acid of 4%,and regenerative method was: 2BV solution at 2 BV/h+2BV solution at 4 BV/h.3. The optimal operation conditions of desalination by TiO2 alloy membrane were found out. Under the condition of system pressure 1.0MPa,surface flow rate 5cm/s,temperature 70℃,the filtration flux of fruit acid effluent was high. Experiment results also shew that the desalination effect of TiO2 alloy membrane could satisfy addition demands, but the malic acid lost very much(≥50%).As a result, the TiO2 alloy membrane was not suitable for the desalination and reutilization of fruit acid effluent.Primary economic benefit evaluation was performed on electrodialysis and ion exchange resin. For a 10t/h color and acid free apple juice production line, the reutilization of malic acid in the effluent could add production value 4～6 million yuan/year. With the same addictive...