Liquid – Liquid Extraction of Hydrochloric Acid from Aqueous Solutions by Tri-n-dodecylamine and Tri-n-octylamine / diluents

Jamal Stas,Hala Alsawaf

doi:10.3311/ppch.8355

Abstract

The extraction of HCl from aqueous solutions using two types of long-chain tertiary amines tri-n- dodecylamine/ kerosene and tri-n-octylamine/ kerosene in the presence of octanol-1 or tributyl phosphate as modifier has been studied. The effect of mixing time, HCl concentration in the aqueous phase, amine concentration, organic to aqueous phase ratio, modifier percentage in the organic phase, NaCl concentration in the aqueous phase and temperature were studied. The effect of some diluents such as: toluene, benzene and xylene on HCl extraction was also investigated and found to follow the order: Benzene > toluene > kerosene + 10% octanol-1 ≈ xylene Tri-n-dodecylamine and tri-n-octylamine showed a great affinity towards HCl in all tested diluents. Both amines (TDA and TOA) can be successfully used for HCl recovery from aqueous acidic solutions. Water was found to be effective to strip HCl from the acid loaded organic phase and more than 95% of HCl can be recovered in three stripping stages at Vaq/Vorg = 20/1 and 75 °C.

Highlights

Hydrochloric acid is an important chemical and widely used in a variety of industries and chemical processes and in some cases as a very successful substitute in processes that otherwise use sulphuric acid
In the present paper we report the partition of hydrochloric acid between water and tri-n- dodecylamine and tri-n- octylamine containing octanol-1 in kerosene and all parameters influencing the extraction process such as: stirring time, acid concentration in the aqueous phase, extractant concentration, modifier percentage in the organic phase, organic to aqueous phase ratio, and the effect of some diluents on the extraction has been investigated
It is obvious that the concentration of hydrochloric acid in the organic phase [HCl]org was increasing in accordance with Le Chatelier’s principle with the increase of hydrochloric acid in the aqueous phase [HCl]aq, until [HCl]org reaches the value of 0.1 M, no changes of [HCl]org was observed in the range of acidity ([HCl]aq = 0.2−3.5M) and the molar ratio of the extracted HCl concentration to the initial tri-n-dodecylamine concentration was equal to 1 ([HC]org/[TDA]i ≈1)

Summary

Introduction

Hydrochloric acid is an important chemical and widely used in a variety of industries and chemical processes and in some cases as a very successful substitute in processes that otherwise use sulphuric acid. A large amount of acidic waste water which is listed as a hazardous waste will be generated from hydrometallurgical and acid pickling industrial units. The recovery of HCl from its aqueous streams is crucial and needed to prevent environmental pollution and to recycle the recovered acid. Tertiary amines such as: Tri-n- dodecyl amine, tri-n-octylamine, Alamine 308 (tri-isooctylamine), TEHA (tri-2-ethyl hexyl amine), Alamine 336 (a mixture of triocty/decyl amine) have been proven to be effective extractant to recover HCl and H2SO4 from aqueous solutions [5,6,7,8]. The extraction reaction of HCl by tertiary amines can be written as follows:

Methods

Results

Conclusion