Novel eco-friendly polyaspartic acid derivative for the control of CaCO3 and CaSO4 scales in reverse osmosis desalination

Eco-friendly antiscalants have recently attracted considerable interest, particularly focusing on the progression of their structures and assessing their effectiveness. Polyaspartic acid (PASP) and a novel derivative, PASP 2-aminoethane sulfonic acid (PASP-SEA), were produced via condensation polymerization. Additionally, two other green antiscalants were included for comparative evaluation: sodium carboxymethylcellulose (CMC) and a citric acid-sodium citrate blend (CA-SC). The inhibition efficiency (IE) of PASP, PASP-SEA, CMC, and CA-SC was assessed through static testing. The saline solution was brine from a reverse osmosis unit supplied by brackish water at 80% recovery. The optimal doses at pH 8.2 and Langelier Saturation Index 2.9 were determined to be 1, 0.25, 0.5, and 5 mg L− 1, respectively. At an antiscalant dose of 1 mg L− 1 and pH 7.07, the IE values were 94, 100, 38, and 29% respectively. Performance improved for all antiscalants with rising ionic strength from 0.321 to 0.363 using NaCl, with IE ranking as PASP-SEA > PASP > CMC > CA-SC. Dynamic testing was performed on PASP and PASP-SEA, revealing a significantly lower scaling rate for PASP-SEAP. PASP and PASP-SEA were characterized using ultraviolet-visible spectroscopy, Fourier transform infrared spectrometer for functional groups, Thermo-gravimetric analysis for thermal properties, Gel permeation chromatography/size exclusion chromatography for average molecular weight, and biodegradability was evaluated using the biochemical oxygen demand method. X-ray diffraction and Scanning electron microscope analyses illustrated crystal deformation. Furthermore, each antiscalant underwent an economic assessment.