DOI: 10.14457/tu.the.2022.770
title: Synthesis and performance of bio-based antiscalant derived from poly (itaconic acid)

description: Scale formation in water-treatment facilities is a critical issue due to serious reductions in the unit’s performance and possible damage to the system. An addition of antiscalants is essential in coping with this problem. However, the majority of these are non-degradable and derived from non-renewable resources, which may cause serious concerns to the environment. Itaconic acid (IA) is an unsaturated dicarboxylic acid produced by biomass fermentation. The material is non-toxic, renewable, and biodegradable. In this work, a process for synthesizing poly(itaconic acid) (PIA) as a bio-based antiscalant is developed. PIA was synthesized by three different methods, i.e., emulsion polymerization, phase inversion emulsification, and free radical polymerization. A suitable method for synthesizing PIA was selected to optimize the effects of pH of IA and initiator concentration on the PIA structure and performance. The chemical structures of the resulting polymer are then characterized by Fourier transforms infrared (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy and gel permeation chromatography (GPC). The inhibition efficiency against a calcium carbonate scale of the synthesized materials is assessed by using inductively coupled plasma-optical emission spectroscopy (ICP-OES). An effective material was selected to investigate their scale inhibition performance. The inhibition mechanism of PIA against calcium carbonate (CaCO3) was investigated. The results show that free radical polymerization is a potential method for synthesizing PIA, at an optimum polymerization time of 4 h at 85 ℃. The variation of pH of IA before polymerization indicated that neutralizing IA to pH 4 enhances the free radical stability and improves the monomer conversion rate to 100 %, while neutralizing IA at pH 9 causes ion repulsion and reduces the monomer conversion rate to 75%. In addition, neutralizing IA to higher pH boosted the deprotonation of COOH, leading to excellent inhibition performance. Increasing the initiator concentration from 5 to 14% improved monomer conversion from 61 to 96%, respectively, due to the generation of free radicals. The reduction of molecular weight based on the initiator dosage is caused by a high possibility of the termination stage during free radical polymerization. However, molecular weight has a potential impact on inhibition efficiency. High molecular weight causes steric hindrance, while low molecular weight limits inhibition ability. Hence the optimum molecular weight is observed at around 28672 Da with a synthesis pH of IA at 9, and 11 % of initiator. The scale inhibition efficiency reached 81% at a dosage of 10 mg/L. The antiscalants concentration, scale concentration, pH of water, and heating time are the main factors influent scale inhibition performance. Based on the morphology analysis of CaCO3 obtained by scanning electron microscopy (SEM), the mechanism of PIA inhibiting CaCO3 can be explained by two possible mechanisms, i.e., stabilizing particle dispersion and crystal modification. The inhibition performance of PIA is comparable to commercial antiscalants, e.g., polymaleic acid (PMA) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC). However, the developed environmentally friendly bio-based material has a high potential for practical applications.