Abstract Concentrated brines and bitterns rejected from various processes contain mineral salts of economic value. For example, sulphate-rich bittern generated at saltworks in the Rajasthan state of India exceeds 3… Click to show full abstract
Abstract Concentrated brines and bitterns rejected from various processes contain mineral salts of economic value. For example, sulphate-rich bittern generated at saltworks in the Rajasthan state of India exceeds 3 million tons annually and requires adequate treatment. Resource recovery from such unutilized by-products presents a sustainable waste management approach. This work presents the development and evaluation of a process for sodium-sulphate (Na2SO4) recovery from sulphate-rich bitterns using an integrated process combining cooling crystallization, filtration, and drying as major unit operations. A parametric study has been conducted to investigate the effect of various operating parameters on product (anhydrous sodium-sulphate) yield and quality. Chemical analysis, TGA, P-XRD, and SEM-EDX techniques were used to characterize the product quality and purity. Based on the parametric studies, a sodium-sulphate production process was designed, and material & energy balance was established. The mass balance calculations have shown that 1 ton of anhydrous Na2SO4 (~97 wt% purity) can be produced from 6.31 tons of bittern having a sulphate ion concentration of about 140.8 ± 6.94 g/l. Subsequently, the economic feasibility of a 5 ton/day anhydrous Na2SO4 capacity plant has been evaluated using the cost and profitability analysis. The engineering-economic calculations suggest that the sodium-sulphate production from bittern can be economically favourable, achieving a payback period of 3.5 years. The optimized parameters and economics presented in this paper could significantly help implement an actual sodium-sulphate recovery unit using sulphate-rich bittern as feed.
               
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