Eco-efficient sea salt purification via coupled brine washing and elutriation technology: A pathway to high-purity salt for sustainable chlor-alkali industry

High-purity sodium chloride (NaCl) is essential for sustainable chlor-alkali production (CAP). Impurities such as Mg²⁺ and Ca²⁺ in raw rock salt accelerate electrode degradation, cause membrane fouling, and reduce the electrolysis efficiency. To address this issue, we developed an integrated purification method that combines brine washing and elutriation. The process began with brine washing to remove water-soluble impurities, followed by elutriation to eliminate insoluble fine particles using an upward fluid flow. This method increased the NaCl purity from 88.0 % to 99.5 %, while significantly reducing the Mg²⁺ and Ca²⁺ contents from 1.44 % to 0.06 % and from 0.69 % to 0.05 %, respectively. XRD analysis confirmed the enhanced crystallinity, with more prominent NaCl peaks at 2θ = 27.5° (111) and 45.4° (220), indicating a more ordered structure. SEM characterization revealed smoother and more uniform crystal surfaces with increased crystal sizes and fewer defects. Furthermore, this process enables brine reuse without compromising performance, minimizing waste generation, and aligning with circular economy principles. Given its high purification efficiency and low environmental impact, this technology is a promising and scalable solution for industrial salt purification, thereby contributing to the long-term viability of the CAP industry.