Recovery of nitric and acetic acids from etching waste solutions using a synergistic system consisting of N235 and TRPO in cyclohexane

摘要

To purify and recover phosphoric acid (H3PO4) from laboratory synthetic etching waste, Alamine 336 (N235) and trialkyl phosphine oxide (TRPO) were used in a mixed extractant to extract nitric (HNO3) and acetic acids (HAc). The effects of the extraction temperature, extractant concentration, and ratio of the organic phase to the liquid phase on the separation process were investigated. Using an organic system containing 3.5% (v/v) N235, 46.5% (v/v) TRPO, and 50% (v/v) cyclohexane, 70% of the HAc and 85% of the HNO3 were extracted, with 8.5% H3PO4 co-extracted through single-stage contact. Furthermore, more than 99% HAc and 99.5% HNO3 were removed after three counter-current extractions, with only similar to 15% of the H3PO4 being co-extracted. A stripping rate of more than 99% was achieved for HNO3, HAc, and H3PO4 using 0.25 mol.L-1 NH3 center dot H2O. UV-vis and FT-IR analyses indicated that the N235 and TRPO mixture had a synergistic effect on HNO3 and HAc extraction. The mechanisms of HNO3 and HAc extraction involve ion-pair association and hydrogen bonding, respectively.