Selective recovery of phosphorus from acid leach liquor of iron ore by garlic peel adsorbent

Abstract

Dephosphorisation of iron ore is an important challenge to the sustainable development of iron-making industry. Hydrometallurgical processing is quite effective in the reduction of phosphorus level from iron ores, where dilute sulfuric acid is commonly chosen as the lixiviant due to its prominent cost-effectiveness. A cheap and effective biosorbent synthesized from garlic peel was proposed in present study to recover phosphorus selectively from acid leach liquor directly under acidic conditions near pH 1–2, allowing high purity phosphorus to be recovered and the residual acid to be recycled for the next round of leaching. This proposal would sharply reduce the dephosphorisation costs of iron ore. Various batch experiments were carried out under different conditions including varying pH, contact time, adsorbent dosages, and metal ion concentration to identify the optimal adsorption parameters for the model solutions. Results showed that the optimal pH for phosphate adsorption was around 1.5 and adsorption equilibrium was attained in 240 min, and the maximum adsorption capacity for phosphate was 1.40 mmol g⁻¹ and 0.81 mmol g⁻¹ at equilibrium pH of 1.5 and 6.5, respectively. A NaOH solution was effective to elute the adsorbed phosphate, and the eluted solution contained mainly Na₃PO₄ and NaOH. Recovery of phosphorus from the iron ore leach liquor by the garlic peel adsorbent was quite effective, and the adsorption efficiency could retain 85% of the original adsorption capability even after five cycles of adsorption and desorption. In summary, the Zr-loaded garlic peel appears a potential low-cost and effective adsorbent for phosphate recovery from the acid leach liquor of high phosphorus iron ore.