Structural effect of diamide extractants on the extraction behaviour of Fe(III) from hydrochloric acid

doi:10.1016/j.hydromet.2016.05.009

Hydrometallurgy

Volume 164, September 2016, Pages 48-53

https://doi.org/10.1016/j.hydromet.2016.05.009 Get rights and content

Highlights

•
The extraction of Fe(III) with three different diamide extractants was compared.
•
The structure of diamides greatly affects the composition of extracted species.
•
Extraction mechanism was confirmed by the DFT and spectral analysis of organic phase.

Abstract

The extraction of Fe(III) from hydrochloric acid with N,N,N′,N′-tetrabutylmalonamide (TBMA), N,N,N′,N′-tetrabutyl-3-oxy-glutaramide (TBDGA) in toluene was studied and compared with the extraction result of N,N,N′,N′-tetrabutylsuccinamide (TBSA) in order to understand the relationship between the chemical structure of the extractants and their Fe(III) extraction behaviors. The extraction efficiency of the extractants toward Fe(III) in toluene increases in the order: TBMA < TBSA < TBDGA. The effect of hydrochloric acid concentration, extractant concentration and temperature on the extraction distribution ratio of Fe(III) was investigated to determine the thermodynamic parameters and the main extracted species. Spectroscopic data (UV–visible and IR) and density functional theory (DFT) were used to clarify the extraction mechanism.

Introduction

Fe(III) is usually present, along with other metals, as an impurity in leaching solutions, such as in the production of rare earth from Baotou Baiyun Obo Rare-earth iron mine in China, and so its separation is of practical importance. Precipitation (Mfandaidza et al., 2008, Jae-Kyeong et al., 2010), adsorption (Navarro et al., 2009), ion exchange (Riveros, 2004, Bethan and David, 2009) and solvent extraction (Biswas and Begum, 1998) are the traditional separation methods of Fe(III). The solid–liquid separation method by precipitation can achieve high separation factor (Mishra et al., 2011) but sometimes have a drawback of poor selectivity (Navarro et al., 2007), whereas ion exchange and adsorption are always used in the treatment of low concentration of target metals.

Solvent extraction is a convenient and common method to purify, concentrate and separate various metals from different aqueous media, and plays an important role in hydrometallurgical industries. For the extraction of Fe(III) from raw materials or industrial waste, organophosphorus acid derivatives, viz. di(2-ethylhexyl) phosphoric acid (DEHPA) have received considerable attention (Tetsuji et al., 1992, Sahu and Das, 1997). This kind of extractants show excellent extractability for Fe(III), but a high acid concentration is required to strip Fe(III) from the acidic extractants. There has been significant interest in recent years in the study on amides as promising alternatives to organophosphorus extractants (Sasaki et al., 2016, Huang et al., 2015, Wu et al., 2016). In comparison with traditional phosphorus-containing extractants, the products of radiolytic and hydrolytic degradation of amides are less detrimental to the separation process and simplified to treat either by incineration or washing (Manchanda and Pathak, 2004, Sun et al., 2003, Gasparini and Grossi, 1986). It is important to reduce the secondary waste in accordance with the CHON principle.

It is well known that the extractant's structure has a great influence on the stability of the extraction species and thus influences the extraction distribution ratio (Cui et al., 2010). As a consequence, optimal structural design of the extractants is an important consideration in the development of extraction technology. Previously, the structure–behavior relations in the extraction studies mainly focus on the organophosphorus acid derivatives (Kalina et al., 1981, Horwitz et al., 1982), only a few papers have reported the structure-reactivity studies on diamide extractants especially tetraalkyldiglycolamide (DGA) extractants(Costa et al., 2003).

In this paper, two kinds of amide extractants, TBMA and TBDGA, were synthesized and the extraction of Fe(III) from hydrochloric acid was studied. The relationship between extraction property and extractant structure was discussed based on the extraction of TBSA (Cui et al., 2015), TBMA and TBDGA.

Section snippets

Materials

All the reagents used in this study were analytical grade. TBMA was synthesized by the reaction of dibutylamine with dimethyl malonate as reported by M. C. Costa (Costa et al., 2003). TBDGA was synthesized by a three-step process as reported in our previous paper (Sun et al., 2010). TBMA and TBDGA were characterized by IR and ¹HNMR. TBMA, yellow oil, 98% purity, IR (KBr, cm^− 1) v_max: 2959, 2932, 2874( C single bond H ), 1638(C double bond O), 1457, 1427(CH₃), 733(CH₂ −); ¹HNMR (400 MHz, CDCl₃, TMS) 3.459–3.400 (s, 2H, COCH₂

Effect of hydrochloric acid concentration on the extraction

The distribution ratios of Fe(III) with TBMA or TBDGA were plotted as a function of hydrochloric acid concentration, respectively (Fig. 2). It shows that the distribution ratio of Fe(III) increases with the hydrochloric acid concentration under the experimental conditions. This phenomenon is similar to the extraction by TBSA in hydrochloric acid medium (Cui et al., 2015). There was a significant increase in the distribution ratio with increasing hydrochloric acid concentration in the range of

Conclusions

The extraction of Fe(III) by TBMA and TBDGA has been investigated from hydrochloric acid into toluene and compared with the extraction result of TBSA in our group. Among these extractants, the extraction capacity for Fe(III) is TBMA < TBSA < TBDGA. The slope analysis result indicates that the extracted species are proposed to be [H·(2TBMA)]⁺[FeCl₄]⁻ and [H·(2TBDGA)]⁺[FeCl₄]⁻, respectively. The extraction reactions of Fe(III) by TBMA and TBDGA from hydrochloric acid medium were exothermic.

Acknowledgements

The authors are grateful for the support from the National Natural Science Foundation of China (21077044, 21171069).

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Structural effect of diamide extractants on the extraction behaviour of Fe(III) from hydrochloric acid

Highlights

Abstract

Introduction

Section snippets

Materials

Effect of hydrochloric acid concentration on the extraction

Conclusions

Acknowledgements

Hydrometallurgy

Hydrometallurgy

Hydrometallurgy

Hydrometallurgy

Hydrometallurgy

Sep. Purif. Technol.

Hydrometallurgy

Hydrometallurgy

Waste Manag.

Hydrometallurgy

Hydrometallurgy

Hydrometallurgy

J. Colloid Interface Sci.

A comparison of various ion exchange resins for the removal of ferric ions from copper electrowinning electrolyte solutions part II: electrolytes containing antimony and bismuth

Hydrometallurgy

Solvent extraction of iron(III) from hydrochloric acid solutions using N,N′-dimethyl-N,N′-diphenylmalonamide and N,N′-dimethyl-N,N′-diphenyl tetradecylmalonamide

Solvent Extr. Ion Exch.