Hydrothermal Decomposition of Strongly Acidic Cation‐Exchange Resin to Valuable Compounds Using Subcritical Water in Alkaline Media

Abstract

AbstractIn this research, hydrothermal technology was used to decompose a strongly acidic Na+ form cation‐exchange resin, DIAION SK1B, containing a crosslinking moiety and a styrene moiety at subcritical water conditions in an alkaline media to obtain decomposed products that can be quickly separated, efficiently collected and recycled. The decomposed materials subjected to a liquid‐solid separation to obtain an aqueous phase containing a salt of a material with an alkali. Two different acids (formic acid and acetic acid) were introduced to the aqueous phase to precipitate the materials and then added to a water‐insoluble solvent to yield materials, to dissolve the precipitated materials into the solvent to obtain a solution containing the materials to be gathered. However, the experiment was performed in a tubular reactor and heated by a salt‐bath. The effects of reaction time, temperature, additives concentration as alkali catalyst and pH of the aqueous solutions on the degradation rate of sulfonated resin were investigated. It was found out that 350°C, 120 min, and 0.05 M NaOH is the optimum condition to attain complete decomposition of this resin. The maximum yield of formic acid in aqueous phase obtained from batch reactor experiments was occurred at optimum conditions. Total organic carbon (TOC) of the aqueous phase reached (38%) to its maximum value at optimum condition. More than 60% of the cation exchange resin was decomposed at optimum condition.