Recovery of high-purity-4-chloroguaiacol from bleaching wastewater by a heterogeneous extraction method

BACKGROUND During the pulping and bleaching processes, 4-chloroguaiacol accounts for a large proportion of chlorine containing pollutants. In this study, a heterogeneous extraction method for extracting 4-chloroguaiacol from the bleaching wastewater by using the intermediate as the solid phase extraction agent is proposed. RESULTS The solid intermediate with the molar ratio of 4-chloroguaiacol to calcium 2:1 is firstly prepared. It is used for reacting with the crude 4-chloroguaiacol in the bleaching wastewater to generate the end solid complex with the molar ratio of 4-chloroguaiacol to calcium 4:1. It is verified to be that the high-purity 4-chloroguaiacol can be released from the simple thermal decomposition of the end solid complex. CONCLUSION At an optimum extraction condition including 30 °C reaction temperature, the pH value of 7, using the deionized water as the solvent, the extraction yield and the purity of 4-chloroguaiacol reached 89.2% and 97.8%. Furthermore, after 15 cycle extraction times, the extraction rate of 4-chloroguaiacol can still reach 86.3%. The extraction yield and the purity of 4-chloroguaiacol reached 68.15% and 99.56% when the guaiacol content was lower than 25 mg/L at the bleaching wastewater. © 2023 Society of Chemical Industry (SCI).