Study On Preparation And Performance Evaluation Of Green Scale Inhibitors For Membrane

Since twenty-first century, microfiltration, ultrafiltration, nanofiltration, reverse osmosis membrane technology have been widely popularized in the world. They were developing in a rapid speed especially in the field of water treatment, which leads to a massive phosphorus membrane scale inhibitor use. The use of such scale inhibitors has brought severe environmental problems as the wastewater contains phosphorus substances flowing into nature which aggravated water eutrophication. Therefore, the study of green membrane scale inhibitor is of great significance. The method of simple preparation of green scale inhibitor, especially, has great application value.This paper expounds the connotation of green membrane scale inhibitor, and discusses the membrane scale inhibitor’s development, classification, performance evaluation methods, research status of green scale inhibitor and scale inhibition mechanism systematically. In terms of the present status that scale inhibitor production mostly use organic synthesis methods which has the disadvantages of complex process and high production cost, the paper mainly discussed the feasibility of using polyepoxysuccinic acid (PESA), poly aspartic acid (PASP), citric acid (AA) and sodium citrate (SC) to prepare for the green membrane scale inhibitor. the paper also introduces the research of the calcium carbonate scale inhibition rate and the calcium phosphate scale inhibition rate which applies EDTA titration and spectrophotometry in the static scale inhibition experiments. The experimental results show that:AA and SC separately compound with PESA and PASP and the mixture shows a good compatibility. The scale inhibition was evaluated based on the rate index.Firstly,14 kinds of mixed monomers are preliminary screened based on literature review and expert consultation. A index system was built to evaluate their environmental effects, their compatibility with other chemical substances, their safety, their economy and their potential innovation. Ultimately four monomer was choosen to be applied to the static experiment.The analysis method of spectrophotometry application on measuring water treatment substances’scale inhibition performance was studied. The comparison between it and EDTA tiltration was studied based on scale inhibition rate as the evaluation index. The results show that the spectrophotometry has a lower data than EDTA tiltration, and its reproducibility is poor. The main reason is the high sample error caused by the sample dilution. Through the independent static scale inhibition experiments of PESA and PASP, their calcium carbonate scale inhibition rate and calcium phosphate scale inhibiton rate was tested. The relationship separately between inhibition rate and dosage, time in a constant temperature, the solution alkalinity and the solution hardness was studied. The optimum condition of test was determined. The best time in a constant temperature is 10h. the study found that the scale inhibition rate would increase to a certain value with the inhibitor add, and it would decrease as the alkalinity and hardness increase.The research applied static scale inhibition experiment method to study the compatibility separately between AA and SC and PESA, and it also use that method to study the material proportion’s effect to the scale inhibition rate. The results show that calcium carbonate scale inhibition of compositions is lower than that of PESA alone. When the composition rate is 10:1 to both compositions, the scale inhibition rate is separately 80.31% and 76.89%, while separate use of PESA can reach the rate 87%. It implies that AA and SC did not play a synergistic effect to PESA. Under the same condition of dosage or proportion, mixture of PESA and AA has a better calcium carbon scale inhibition effect compared to PESA and SC. The calcium phosphate scale inhibition shows similar characteristics.he research applied static scale inhibition experiment method to study the compatibility separately between AA and SC and PASP, and it also use that method to study the material proportion’s effect to the scale inhibition rate. The results show that calcium carbonate scale inhibition of compositions is lower than that of PASP alone. When the composition rate is 10:1 to both compositions, the scale inhibition rate is separately 78.92% and 75.27%, while separate use of PASP can reach the rate 83%. It implies that AA and SC did not play a synergistic effect to PASP. Under the same condition of dosage or proportion, mixture of PASP and AA has a better calcium carbon scale inhibition effect compared to PASP and SC. The calcium phosphate scale inhibition shows similar characteristics.A comparative analysis of the cost of the calcium carbonate scale inhibitor between one substance and compound mixture was studied from a economic point of view. The cost for every 1% percent of the scale inhibition rate was studied, and the results show that adding AA has a higher than using PESA or PASP alone, while adding SC has a small difference with using PESA or PASP alone. So the conclution from economic view is compound contains AA has no advantage while compound contains SC has, and SC can play the role fo alternative at low dosage.