Synthesis and Performance Study of Maleic Anhydride Binary Water Treatment Agent

. A binary copolymer water treatment agent was synthesized by using maleic anhydride and sodium allyl sulfonate as raw materials and ammonium persulfate as initiator. The scale inhibition and dispersion properties of the copolymer were studied through static experiments. The results show that the binary water treatment agent has excellent scale inhibition and dispersion performance. Moreover, the polymer is an environment-friendly agent with good application prospects.


Introduction
The application of circulating cooling water is essential in industry, but the repeated use of cooling water increases the concentration of scaling ions in the water [1][2][3][4][5].This leads to the formation of scale in the form of precipitation on the apparatus, resulting in a significant decrease in the efficiency of the equipment and, in more serious cases, making it impossible for the equipment to operate properly [6][7][8]. At this point in the system is very necessary to add water treatment agent. The effective ions in the water treatment agent will react chemically with the scale forming ions in the cooling water so that scale cannot be formed. That is, the addition of water treatment agents large can alleviate the scaling phenomenon in the water system [9][10][11][12].
In this study, a binary polymeric water treatment agent was synthesized using maleic anhydride and sodium allyl sulfonate as raw materials. Both raw materials contain double bonds and they can undergo polymerization under certain conditions. Moreover, the carboxylic acid groups and sulfonic acid groups contained in the raw materials can make the synthesized polymer have excellent scale inhibition and dispersion properties.

Experiment apparatus
Electronic balance, electric thermostatic water bath, double-beam UV spectrophotometer, collector magnetic stirring thermostatic water bath, vacuum drying oven, magnetic stirrer.

Synthesis of the copolymer
We first weighed a certain amount of raw material maleic anhydride and sodium allyl sulfonate into a four-neck flask, added deionized water to dissolve, and the system was warmed up to 90°C. After that, a certain proportion of ammonium persulfate and isopropyl alcohol were added, while nitrogen gas was introduced into the system. When the system is filled with nitrogen, a syringe pump is used to inject the oxidation-reduction system into the system, i.e., a certain amount of 30% hydrogen peroxide and 10% sodium bisulfite solution. The system was kept at a constant temperature for 6 hours to obtain the final product as an amber liquid (MA/SAS copolymer).
The obtained liquid product was repeatedly washed with anhydrous ethanol to obtain a creamy yellow viscous solid. Finally, it was washed again with formaldehyde and dried in a vacuum drying oven at 60°C. The final milky white solid was obtained as the copolymer agent after purification.
The reaction equation is:

Evaluation of the scale inhibition performance of agents against CaCO3
According to the national standard GB/T16632-2008. Prepared water containing a certain concentration of agent (calcium ion concentration of 600 mg · L -1 and bicarbonate concentration of 1200 mg·L -1 ) was added to the conical flask. The conical flask was subjected to a water bath at 80 °C for 10 hours. The calcium ion concentration in the clear solution was titrated after taking out and cooling, and the scale inhibition rate η 1 was calculated. (2)

Equation 2: Calculation formula of scale inhibition rate
Where C 0 represents the post-experimental calcium ion concentration in blank solution, C 2 is the postexperimental calcium ion concentration in the presence, and C 1 represents the calcium ion concentration in raw water at room temperature, all in mg·L -1 .

Determination of the dispersion performance of the agent
500 mL of prepared water containing different concentrations of agents (150 mg·L -1 for Ca 2+ , 10 mg • L -1 for Fe 2+ in terms of CaCO 3 ) was added to a conical flask, strongly stirred and then water-bathed at 50 °C for 5 hours. After cooling, the transmittance of the upper clear layer of the solution was measured (3 cm colorimetric tube at 450 nm). The light transmittance of distilled water was 100%, and the smaller the light transmittance of the clear solution, the better the dispersion effect.

Study of scale inhibition performance of pharmaceuticals
The scale inhibition performance of the synthesized agent against calcium carbonate was studied, and the experimental results are shown in Figure 1. It can be seen that the scale inhibition performance of the copolymer against calcium carbonate tends to increase with the increasing dosage. At the dosage of 20 mg • L -1 , the scale inhibition rate of calcium carbonate can reach 100%. The scale inhibition rate of the polymer to calcium carbonate is mainly due to the carboxylic acid group contained in the copolymer, which can chelate with calcium ions in water, and it will not precipitate in the form of calcium carbonate scale after occupying the calcium ions, which plays the role of scale inhibition.

Study on the dispersion performance of the agents
As Figure 2 shows the results of the dispersion performance study of the copolymer, after the two monomers were polymerized, the copolymer exhibited excellent dispersion performance. After the copolymerization of maleic anhydride and sodium allyl sulfonate, the copolymer contains sulfonic acid groups, which have certain chelating ability with iron ions in water, which will make the iron oxide can be uniformly dispersed in the solution and washed away with water. As can be seen from the figure, the translucency of the upper clear solution after dispersing iron oxide is 35% when the addition amount of polymer is 20 mg • L -1 . The water treatment agent has excellent dispersion effect.

Conclusion
(1) An environmentally friendly water treatment agent without phosphorus and nitrogen was synthesized by using maleic acid and sodium allyl sulfonate as raw materials.
(2)The scale inhibition and dispersion performance of the copolymer was studied by static experimental method, and the result is that the agent has excellent scale inhibition and dispersion performance, which is an excellent scale inhibition and dispersion agent for circulating water.
(3)The binary water treatment agent does not contain phosphorus and nitrogen in the molecule, is a green and environmentally friendly agent, long-term use will not cause eutrophication of water bodies, and has good application prospects.
(4) In the future, we want to further strengthen the research on water treatment technology and hope to further reduce the use of drugs.