The Treatment And Resources Recycling Technology Of The Mother Liquor In Caffeine Production Process

The mother liquor is from the caffeine production process, which is a high concentration of biodegradable organic wastewater. The characteristics of the wastewater are high salinity, high COD content,deep color, complicated components and large amount. At present the caffeine wastewater treatment method is rarely reported, and China is a big caffeine-producing country, therefore, it has far-reaching significance to find an economical and applicable technique of wastewater treatment with high efficiency to protect the water environment and promote the development of caffeine production in China.Two technologies have been designed by the author, the first is the direct use of physical-chemical technology to reduce mother liquor's COD, and the second is the resources recycling technology of caffeine mother liquor. the principal research results are as follows: Ⅰ. The COD reduction technology of caffeine mother liquorIn this paper, extraction-adsorption-oxidation method is used to treat caffeine mother liquor, and the effect on its COD removal rate is studied.1. Using TBP as extractant and kerosene as diluents, TBP and kerosene ratio is 1:1, under room temperature extraction time is 15min, agent water ratio is 1:1, the single COD removal rate of caffeine mother liquor is up to 45%.2. Utilizing powdered activated carbon as adsorbent to treat caffeine mother liquor after extraction, the amount of activated carbon is 18g(six batches) in 95mL caffeine mother liquor, under room temperature adsorption time is 40min, the COD removal rate of caffeine mother liquor is 90%.3. Using NaClO-Fenton to treat caffeine mother liquor after extraction and adsorption. the amount of NaClO(10-15% available chlorine content) and H2O2(30%) are both 0.8mL, the amount of 0.1mol·L-1 FeSO4 is 0.4mL, pH is 3, under room temperature reaction time is 40min, the COD removal rate of caffeine mother liquor is above 95%. At last, using 3g activated carbon to deal with treated water, under room temperature adsorption time is 40min, the COD removal rate of caffeine mother liquor is up to 98.85%.Ⅱ. The resources recycling technology of caffeine mother liquorThrough the composition and characteristics of caffeine mother liquor analysis, the recyclable components in this caffeine wastewater are HAc and Na2SO4, and their concentrations are 0.5mol·L-1 and 0.84mol·L-1. The design uses a process handle rather than the end of treatment technology. The treated water is applied directly to the corresponding production processes. Through the recycling of treated water resources, it has significantly reduced the amount of wastewater, and other resources have achieved efficient cycle. It has not only achieved the environment objective of energy saving, but also good economic benefits.1. The high concentration SO42- in caffeine mother liquor is converted into gypsum by quicklime chemical precipitation method, the single conversion of SO42- is up to 86%, the gypsum purity as high as 95%, which has certain economic and practical value.2. Through the method of chemical precipitation, Na+ with high concentrations in the caffeine mother liquor is converted into NaHCO3, with yield 78%, purity 92%.3. The acetic acid is isolated and recycled from caffeine mother liquor using extraction method to reduce the side effects on the entire cycle. With tributyl phosphate (TBP) as extractant, agent water ratio is 1:1, the single recovery rate of acetic acid is about 53%.4. Through the above process, the treated water is applied directly to the production system, after many times of recycling, SO42- removal rate,CaSO4 and NaHCO3 yield and purity,HAc recovery effects and purple acid urea(1,3-dimethyl-4-imino-5-nitrosourea hydrochloride) production has good stability.