Avraham Baniel

New Process for Recovery of Zinc Sulfate and Sulfuric Acid from Zinc Electrowinning Bleed Solutions

ABSTRACTAcid-base couple extractants extract sulfuric acid and zinc sulfate efficiently, selectively and reversibly. Their properties allowed development of a new, solvent extraction process for treating zinc electrowinning waste streams. In this process, about 95% of the sulfuric acid and 95% of the zinc can be recovered at concentrations high enough to be directly recycled to zinc production. Lime consumption and gypsum formation are substantially reduced. Only one extractant is used in the process, and zinc is recovered as zinc sulfate.

SULFURIC ACID RECOVERY THROUGH SOLVENT AIDED DECOMPOSITION OF AMMONIUM SULFATE.

ABSTRACT A process for the recovery of sulfuric acid through anmonium sulfate (I) is described. This process is based on extraction-aided disproportionation of anmonium hydrogen sulfate to ammonium sulfate and sulfuric acid. Acid-base couple solvents were found to be more suitable for this process than oxygenated solvents as they can operate at higher temperatures and concentrations. A solvent composed of 0.50M methyl tricaprylyl ammonium salt of dinonyl naphthalene sulfonic acid in aromatics-free white spirits, was chosen. Sulfuric acid, at a concentration of about 35%, can be obtained from the H2SO4-(NH4)2SO4-H2O system. This disproportionation may be applied to recover sulfuric acid from gypsum. CaSO4 is converted in reaction with carbon dioxide, anmonia and water to CaCO3 and ammonium sulfate, which is thermally decomposed to ammonia and ammonium hydrogen sulfate. The overall process is equivalent to the displacement of H2SO4 from CaSO4. by means of CO2 and thermal energy.

WET PROCESS PHOSPHORIC ACID DEFLUORINATION BY AMINE-BASED EXTRACTANTS

Abstract Defluorination of WPA to feed grade levels (P:F > 100) was found to be effective with acids of low Al content. Acids with higher Al levels cannot be defluorinated effectively due to a sharp decrease in the distribution coefficient of the fluorine. This is attributable to complexation of fluorine by Al. An important part of manufactured phosphoric acids contain aluminum in levels that render defluorination to feed grade requirements impractical. Treating such acids with SiO2 as well as preconcentration prior to extraction result in some improvement in extractability but provides for marginal improvements only.

A PROCESS FOR DEFLUORINATION AND PURIFICATION OF WET PROCESS PHOSPHORIC ACIDS CONTAINING HIGH Al CONCENTRATIONS.

Abstract A solvent extraction process is described for defluorination and desulfation of filter phosphoric acids with high Al content. The solvent used contain an amine and phosphoric acid as main constituents. The acid obtained is compatible with feed-grade requirements. It can be concentrated to 56–60% P2O5 by multiple effect evaporation, decreasing steam requirements by 50%. If an acid-base couple solvent is used in this process, part of the extracted phosphate can be recovered by back-wash with water in the form of highly purified phosphoric acid low in metals, fluorine and sulfate. The remainder of the acid along with the extracted sulfate is obtained as ammonium salt. The extracted F is converted into crystaline alkali fluorosilicate.