Methallylsulfonate Polymeric Antiscalants for Application in Thermal Desalination Processes

Nine copolymers of acrylic acid and sodium methallyl sulfonate were tested as scale inhibitors in thermal desalination. The nine antiscalants covered molar masses between 2000 and 9500 g.mol^-1 and concentrations of sulfonated monomer ranging between 10 and 30 mole percent. A pressure measurement and control (P-MAC) unit and a high-temperature pressurized vessel were used to measure the effectiveness of the scale inhibitors in seawater, concentrated seawater, and model solutions at 125 °C. The effectiveness of the novel copolymers was comparable to commercial antiscalant at times up to 15 min and improved at longer times. Molar mass was a more important determinant of effectiveness than degree of sulfonation, with the greatest mitigation of calcium sulfate precipitation observed for antiscalants of molar mass 2000 to 2500 g.mol^-1 regardless of sulfonate content. Antiscalants of molar mass 4500 to 5000 g.mol^-1 showed a higher threshold effect than antiscalants of molar mass 7000 to 9500 g.mol^-1, with a 30% sulfonated polymer of molar mass 4500 g.mol^-1 performing appreciably better than other polymers of a similar molar mass.