Potassium sulphate production from an aqueous sodium sulphate from lead-acid battery recycling: Impact of feedstock impurities on products yields

The increasing demand for renewable energy highlights the need for efficient energy storage solutions. Despite various available technologies, lead-acid batteries remain preferred for many industrial applications due to their inherent advantages. However, their expanded use necessitates proper waste management and recycling practices. During lead-acid battery recycling, Na₂SO₄ is generated as a waste product, which cannot be directly sold due to quality concerns and limited market demand. Consequently, advanced waste management techniques are required to comply with government regulations on industrial waste disposal. Despite these challenges, Na₂SO₄ serves as a vital precursor for producing K₂SO₄, a valuable fertilizer. Prior research on the glaserite process for converting Na₂SO₄ to K₂SO₄ has assumed Na₂SO₄ to be pure—without traces of impurities. However, Na₂SO₄ recovered from battery recycling contains various contaminants. To address this, HSC Chemistry software was used to model K₂SO₄ and NaCl production from impure Na₂SO₄ and KCl, considering feed impurities. Under ideal conditions—a 1 bar pressure, 25°C feed temperature, and 40°C reactor temperature—over 90% yield of K₂SO₄ and NaCl was achieved in the absence of impurities. However, the addition of impurities resulted in a reduction in yields. Notably, impurity levels ranging from 1% to 4% by weight still allowed for yields exceeding 90%. Furthermore, a review of reactor compositions revealed a significant depletion of potassium and chlorine ions which are crucial for K₂SO₄ and NaCl production as impurity levels varied from 0% to 10%. These findings emphasize the negative impact of impurities on K₂SO₄ and NaCl yields.