Effective adsorption of phosphoric acid by UiO-66 and UiO-66-NH2 from extremely acidic mixed waste acids: Proof of concept

摘要

Streams of waste mixed acids from conventional wet etching processes contain high levels of H3PO4, which warrant recycling. This investigation is the first to use metal organic framework UiO-66 and UiO-66-NH2 to adsorb phosphoric acid from waste mixed acids from the world's largest semiconductor foundry, a synthetic HNO3-H3PO4-HAc mixture, and 85% phosphoric acid. Both UiO-66 and UiO-66-NH2 have high capacities to adsorb H-3 PO4 in extremely acidic solutions. The Langmuir adsorption capacities (q(max')s) of UiO-66 for waste mixed acids and a synthetic HNO3-H3PO4-HAc mixture on UiO-66 at 25 degrees C are 3360 and 8,510 mg-H3PO4/g, respectively, and that of 85% phosphoric acid on UiO-66 is 4,790 mg-H3PO4/g. The qrnax of UiO-66-NH2 for phosphoric acid from 25% to 75% waste mixed acids is 4550 mg-H3PO4/g, which exceeds that of UiO-66. The corresponding P:Zr ratio for adsorbed MOF is in the range 6.2-13.5, suggesting that the tested MOF crystals are super-adsorbents of phosphoric acid under extremely acidic conditions. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.