Comparative analysis of the effectiveness of green antiscalants and SHMP for calcium sulfate scale control

Insufficient research on green antiscalants necessitates further investigations. In a comparative study, sodium hexametaphosphate (SHMP), a non-green antiscalant, was assessed alongside three green antiscalants: a citric acid and sodium citrate mixture (CA-SC) with a 1:1 molar ratio, polyaspartic acid (PASP) and sodium carboxymethyl cellulose (CMC). The saline solution 30 mM CaSO₄. The inhibitory efficiency (IE. %) of each antiscalant was determined based on dosage, pH and ionic strength (I) using the standard static test. Additionally, the current prices of the antiscalants were evaluated. PASP was identified through FTIR and GPC/SEC analyses. While XRD was employed to characterize the CaSO₄ crystals. The polymeric green antiscalants, PASP and CMC, exhibited higher IE.%. At the same pH, I and dosage PASP and CA-SC demonstrated an IE. of 96%, SHMP had 80% and CMC had 58%. Antiscalant performance was better in basic conditions than in acidic conditions, although CMC showed a consistent performance across both environments. An increase in I resulted in an increase in IE. %, but SHMP and CA-SC exhibited alternating IE. % due to variations in electrostatic interactions. PASP and CMC are a promising green antiscalants; however, PASP requires some structural modifications to enhance efficacy and reduce industrial production costs. In contrast, CMC needs a controlled dosage for ease of application.