关键词: 电化学, 降解, 有机磷, 回收, 磷酸钙

Abstract:

To bridge the gap between phosphonates being too much as the antiscalant used in industrial cooling water systems and phosphorus being too little as a resource, the electrochemical treatment process was developed for the recovery of phosphorus from the phosphonate wastewater. In this reaction system, boron doped diamond (BDD) mediated anodic oxidation was effective for the oxidative release of ortho-phosphate (o-PO₄) from phosphonates. At the same time, OH^- was generated by H₂O reduction at the cathode and created a basic environment near the cathode, where calcium phosphate would become highly supersaturated precipitated. In this study, the effects of operation parameters on ethylene diamine tetra(methylene phosphonic acid) (EDTMP) degradation and the recovery of phosphorus were investigated. It was found that the degradation of EDTMP was mainly attributed to the production of ?OH during the BDD mediated anodic oxidation process, which was much more favorable at higher current density. TOC removal efficiency, o-PO₄-P concentration and phosphorus recovery efficiency were increased from 14% to 72%, 6.5mg/L to 9.9mg/L and 21% to 83%, respectively, with current density increasing from 3mA/cm² to 30mA/cm². Phosphorus recovery efficiency was negligibly influenced by the variation of solution pH from 3.0 to 12.0. Increasing Ca²⁺ concentration could increase the recovery of phosphorus. Phosphorus recovery efficiency was enhanced from 46% to 83% with elevating Ca²⁺ concentration from 25mg/L to 100mg/L. In electrochemical reaction system, phosphorus was recovered at the cathode surface in the form of amorphous calcium phosphate with Ca/P molar ratio of 0.6.

Key words: electrochemistry, degradation, organophosphorus, recovery, calcium phosphate