Novel eco-friendly antiscalant for major inorganic scaling control: laboratory tests and scale-up in a pilot RO unit†

Abstract

Eco-friendly antiscalants have garnered considerable interest, particularly regarding their structural development and performance assessment. In this study, polyaspartic acid (PASP) and a novel derivative, polyaspartic acid–2 amino ethane sulfonic acid (PASP–SEA), were synthesized. For comparative analysis, two additional green antiscalants were utilized: sodium carboxymethylcellulose (CMC) and a citric acid–sodium citrate (CA–SC) mixture. The inhibition efficiency (IE, %) of PASP, PASP–SEA, CMC, and CA–SC was evaluated through static tests. A saline solution was derived from a brine RO unit. The optimal doses determined at pH 8.2 and an LSI of 2.9 were 1, 0.25, 0.5, and 5 ppm for PASP, PASP–SEA, CMC, and CA–SC, respectively. At an antiscalant concentration of 1 ppm and pH 7.07, the IE was in the order PASP–SEA > PASP > CMC > CA–SC, with values of 94%, 100%, 38%, and 29%, respectively. All the antiscalants exhibited improved performance with increasing ionic strength (I). Dynamic tests were performed on the antiscalants using a pilot RO unit, revealing a significantly lower scaling rate for PASP–SEA. UV-vis spectroscopy, FTIR spectroscopy, and GP/SEC analyses confirmed PASP–SEA synthesis. While PASP–SEA was slightly less biodegradable than PASP, it exhibited superior thermal stability, and XRD and SEM analyses revealed its optimal performance with the highest crystalline deformation. Furthermore, an economic assessment of each antiscalant was conducted.