Synthesis, characterization and performance evaluation of an environmentally benign scale inhibitor IA/AMPS co-polymer

With increasing awareness and efforts on 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 spectroscopy was employed for co-polymer identification. The morphology and phase structure of the scales were analyzed via SEM and XRD. The effects of the reaction time/temperature, the ratio of monomers, and the dosage and ratio of initiators used on the dispersion properties and the scale inhibition performance of the co-polymer were systematically investigated to obtain optimized synthesis conditions. The results show that an IA/AMPS co-polymer with the best dispersion index (51.10 mg g−1) can be prepared based on the following reaction conditions: 1 : 2 (molar ratio of IA and AMPS), 7% (dosage of initiators: total mass of monomers), and 4 : 1 (molar ratio of initiators ammonium persulfate: sodium bisulfite), at 95 °C (reaction temperature) and 5 hours (reaction time). The results of static scale inhibition tests demonstrate that the inhibition efficiency of IA/AMPS (14 mg L−1/18 mg L−1) towards CaCO3/CaSO4 is about 81.2%/80.6%, respectively. TGA analysis reveals that obvious thermal degradation of IA/AMPS does not occur up to 345 °C and above, which means that the co-polymer has excellent temperature resistance. In addition, the interactions between the IA/AMPS co-polymer and the CaCO3/CaSO4 scale crystal were calculated by molecular dynamics (MD) simulation. The results show that the binding strength of IA/AMPS with the (10) surface of the calcite crystal is firmer than that with the (104) surface, while the binding energies of IA/AMPS with the two surfaces of the anhydrite crystal, (001) and (010) planes, are nearly equal. In a word, the IA/AMPS co-polymer is a very promising scale inhibitor not only for CaCO3 but also for CaSO4.