Solvent extraction of calcium ion from cation-exchange resin regeneration wastewater using D2EHPA and saponified D2EHPA

Abstract

Solvent extraction experiments of Ca²⁺ with D2EHPA and 15% saponified D2EHPA from cation-exchange resin regeneration wastewater have been performed. Compared with the extraction efficiency (E) of Ca²⁺ with D2EHPA, the use of 15% saponified D2EHPA significantly increases the extraction efficiency (E) of Ca²⁺. In this work, a systematic study on the extraction of Ca²⁺ from cation-exchange resin regeneration wastewater using saponified D2EHPA has been carried out. To study the extraction efficiency and advantages of the method in the removal of Ca²⁺, various parameters such as saponification ratio of D2EHPA_, D2EHPA mass fraction, reaction temperature, phase mass ratio, initial pH of wastewater, transfer-speed, and transfer-time are studied and optimized. The results show that Ca²⁺ in wastewater can be effectively removed by saponified D2EHPA. An extraction efficiency of more than 99.9% is attained at the optimized parameters and the cation-exchange resin regeneration waste-water can be discharged directly by two levels of extraction, and it meets the Chinese National Emission Standards.

Keywords:

• D2EHPA
• Saponified D2EHPA
• Ca²⁺ from regeneration wastewater
• Extraction

Acknowledgement

The authors gratefully acknowledge the financial support of this work by the New Century Excellent Talents of Ministry of Education (NCET-07-0577), the People’s Republic of China.