Abstract

Solvent extraction is an effective method for purufucation of wet process phosphoroc acid. The aim of this study was purification of wet-process phosphoric acid using acid grade phosphorus pentoxide and minimization of fluoride and arsenic. The first step included the pre-purification which was done by discoloration of acid and clarification during which the impurities were reduced. Fluoride reduction rate of about 68% was significant at this step. In the following step, liquid-liquid extraction was used to purify the phosphoric acid from previous stage. The parameters of phase ratio, two-phase contact time and the fluid flow regime in a packed column of the fluidized bed were studied using 2-ethylhexanol as a basic solvent. The results of this part have been used as an evaluation of acid extraction yield and separation factor of impurities using an experiment designed by the Taguchi method. Arsenic, fluoride and phosphorus pentoxide concentration were measured using Inductivity Coupled Plasma (ICP) and Ion Chromatography (IC) analysis. The optimal level of parameters and their effect was obtained. By comparing the optimal and worst level in extraction step, it was found that the amount of acid extracted can vary from 23% to 73%. Furthermore, the removal rate of 49% for fluoride and 67% for arsenic in the worst conditions, can increase to the optimal conditions as much as 72% and 93%, respectively. The overal removal rate of 92% for fluoride and 96% for arsenic in two stages were achieved. Increasing of phase ratio, the time as well as increasing the flow regime created optimal conditions in the extraction section.

摘要

溶剂萃取是湿法磷酸精制的有效方法。本研究的目的是使用酸级五氧化二磷纯化湿法磷酸，并最大限度地减少氟化物和砷。第一步包括通过酸变色和澄清过程中杂质减少的预纯化。在此步骤中，约 68% 的氟化物减少率是显着的。在接下来的步骤中，液-液萃取用于纯化前一阶段的磷酸。以2-乙基己醇为碱性溶剂，研究了流化床填充柱的相比、两相接触时间和流态等参数。使用田口法设计的实验，将这部分的结果用作酸提取率和杂质分离系数的评价。使用电感耦合等离子体 (ICP) 和离子色谱 (IC) 分析测量砷、氟化物和五氧化二磷的浓度。获得了参数的最佳水平及其效果。通过比较提取步骤中的最佳和最差水平，发现提取的酸量可以在 23% 到 73% 之间变化。此外，在最差条件下对氟化物的去除率为 49%，对砷的去除率为 67%，可以分别提高到 72% 和 93% 的最佳条件。两个阶段的总去除率达到了92%的氟化物和96%的砷。增加相比，