Effective Adsorption of Congo Red from Aqueous Solution Using Fe/Al Di-Metal Nanostructured Composite Synthesised from Fe(III) and Al(III) Recovered from Real Acid Mine Drainage.

Hendrik Brink,Vhahangwele Masindi,Khathutshelo Muedi,Johannes Maree,Nils Haneklaus

doi:10.3390/nano12050776

Abstract

This study presents the first known exploration of Congo red dye (CR) adsorption by a polycationic Fe/Al Di-metal nanostructured composite (PDFe/Al) synthesised using Fe(III) and Al(III) recovered from authentic acid mine drainage (AMD). The PDFe/Al successfully removed CR from the aqueous solution. The mineralogical, microstructural, and chemical properties of the synthesised PDFe/Al adsorbent (before and after adsorption) were studied using state-of-the-art analytical instruments. The optimum conditions were observed to be 100 mg·L−1 CR, 1 g of the PDFe/Al in 500 mL adsorbate solution, 20 min of shaking, pH = 3–8, and a temperature of 35 °C. At optimised conditions, the PDFe/Al showed ≥99% removal efficacy for CR dye and an exceptionally high Langmuir adsorption capacity of 411 mg·g−1. Furthermore, a diffusion-limited adsorption mechanism was observed, with two distinct surfaces involved in the adsorption of CR from an aqueous solution. It was determined that the adsorption of CR induced internal strain and deformation within the matrices and interlayers of the PDFe/Al which resulted in a marked increase in the adsorbent pore surface area and pore volume. The remarkably high adsorption capacity could be attributed to the high surface area. A regeneration study showed that the adsorbent could be reused more than four times for the adsorption of CR. The findings from this study demonstrated the feasibility of recovering valuable minerals from toxic and hazardous AMD and demonstrated their potential for the treatment of industrial wastewaters.

Highlights

Environmental contamination by coloured, acidic, and metalliferous effluents has been an issue of topical concern globally [1,2]
Mining is inevitably expected to grow in many countries since it contributes to the gross domestic products (GDPs), job creation, and socio-economic development of any given country with good mineral endowments
A value for nS < 1 indicates a cooperative reaction between sorption sites and n sorbate molecules; this type of adsorption is characterised by sigmoidal adsorption isotherm data

Summary

Introduction

Environmental contamination by coloured, acidic, and metalliferous effluents has been an issue of topical concern globally [1,2]. This is fuelled by the magnitude of ecological and toxicological impacts posed by these wastewater streams to the receiving environment [3–5]. The problem of environmental contamination by coloured effluents, mainly from textile, pulp, paper, leather, and paint industries, is expected to grow primarily due to the rapid growth in population that will place proportional demand on resources to render goods. The future mining prospects project that the generation of AMD will prevail into the future [13]. Be that as it may, stringent regulatory frameworks require

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Results

Conclusion