Synthesis, characterization and performance evaluation of the environmentally benign scale inhibitor IA/AMPS copolymer
Abstract: With the increasing awareness and efforts for environmental protection, developing non-phosphorus and biodegradable scale inhibitors is becoming a hot research topic. In this work, an environment-friendly scale inhibitor was synthesized by free radical polymerization with Itaconic acid (IA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS). FTIR spectrometry was employed for copolymer identification. Morphology and phase structure of the scales were analyzed via SEM and XRD. The effects of reaction time/temperature, the ratio of monomers, the dosage and ratio of initiators used on the dispersion property and scale inhibition performance of the copolymer were systematically investigated to obtain the optimized synthesis conditions. Results show that IA/AMPS copolymer with best dispersion index (51.10 mg•g-1) can be prepared through the following reaction conditions: 1:2 (molar ratio of IA and AMPS), 7% (dosage of initiators: total mass of monomers), 4:1 (molar ratio of initiators, ammonium persulfate: sodium bisulfite), 95°C (reaction temperature) and 5 hours (reaction time). The results of static scale inhibition tests demonstrate that the inhibition efficiency of IA/AMPS (14mg•L-1/18mg•L-1) towards CaCO3/CaSO4 is about 81.2％/80.6％, respectively. TGA analysis reveals that obvious thermal degradation of IA/AMPS doesn’t occur until 345℃ and above, which means the copolymer has excellent temperature resistance. In addition, the interactions between IA/AMPS copolymer and CaCO3/CaSO4 scale crystal were calculated through molecular dynamics (MD) simulation. Results show that the binding strength of IA/AMPS with the (110) surface of calcite crystal is firmer than that with the (104) surface, while the binding energies of IA/AMPS with the two surfaces of anhydrite crystal, (001) and (010) planes, are nearly equal. In a word, IA/AMPS copolymer is a very promising scale inhibitor not only for CaCO3 but also for CaSO4.