Ferric Phosphate Recovery From Acidic Semiconductor Wastewater via Acid-Induced ZVI Dissolution and Oxidative Precipitation.

The semiconductor industry generates substantial volumes of acidic wastewater containing high phosphorus concentrations, necessitating effective treatment and a resource recovery strategy. This study proposes an integrated process for phosphorus recovery based on acid-induced dissolution of zero-valent iron (ZVI) coupled with oxidant-assisted ferric phosphate precipitation. Acidification significantly enhanced ferrous ions (Fe2+) release from ZVI, facilitating efficient phosphorus capture through subsequent oxidation and ferric phosphate formation. Complete phosphorus removal was achieved at an oxidant-to-Fe2+ molar ratio of 0.5 using either H2O2 or NaOCl. Oxidation-reduction potential (ORP) values of 500 mV for H2O2 and 1000 mV for NaOCl were established as critical setpoints for precise oxidant dosing and process control. Continuous-flow experiments demonstrated stable P-removal efficiency over a broad range of influent conditions while producing sludge with favorable setting characteristics. Furthermore, calcination transformed recovered amorphous ferric phosphate into crystalline strengite, highlighting its potential for beneficial reuse and resource recovery. Economic analysis revealed total chemical costs at 3.24 and 3.53 USD/kg-P for H2O2- and NaOCl-based systems, respectively. These findings demonstrate that the proposed ZVI approach provides a technically robust, economically attractive, and sustainable strategy for phosphorus recovery and recycling circularity in acidic semiconductor wastewater treatment.