Inhibition of calcium sulfate scale by poly (citric acid)

• Condensation polymerization of citric acid successfully prepared Poly (citric acid).
• Poly (citric acid) has excellent inhibition performance for CaSO4 scale.
• Poly (citric acid) decreases deposit of CaSO4 crystals in simulated scaling water.
• Poly (citric acid) can distort CaSO4 crystal polymorphs.

Condensation polymerization of citric acid successfully prepared Poly (citric acid). The polymerization product has characterized by FTIR and UV spectroscopy. The polymerization has confirmed to perform well and there are suspended carboxylic groups on the polymer molecules. Inhibition performance of new obtained poly (citric acid) for CaSO4 scale has evaluated by static scale inhibition method. When the dosage of polymer scale inhibitor is 2.5 mg/L in initial simulated scaling aqueous solution in which the ion concentrations of Ca2 + and SO42 − are both 2040 mg/L, the scale inhibition rate exceeds to 90%. When the dosage of polymer scale inhibitor is 25 mg/L, the scale inhibition rate is up to 98.8%. All of the results indicate that poly (citric acid) increase the Ca2 + ion concentration in heated simulated scaling water and decrease the deposit of CaSO4 crystals. The CaSO4 crystals collected from simulated scaling water observed by SEM and characterized by FTIR and XRD. The results illustrate that the polymer inhibitor evidently affects the procedure of scale crystal growing. Poly (citric acid) might absorb on the surface of CaSO4 scale crystals and distort the CaSO4 scale crystal polymorphs. Therefore, poly (citric acid) could use as a kind of potential CaSO4 scale inhibitor.

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