Synthesis, Characterization, and Application of Functionalized Silica–Carbon Hybrid Nanoparticles for the Treatment of Acidic Cu(II)‐Contaminated Water

• Published in: Clean : soil, air, water air, water, 2017-02, Vol.45 (2), p.np-n/a
• Main Authors: Etale, Anita, Tavengwa, Nikita, Tutu, Hlanganani, Drake, Deanne C.
• Format: Article
• Language: English
• Subjects: Acid mine drainage; Adsorbents; Adsorption; Carbon; Carbonization; Nanoremediation; Organic–inorganic composites; Sorption
• ISSN: 1863-0650; 1863-0669
• DOI: 10.1002/clen.201500873

A novel amine‐functionalized inorganic–organic hybrid adsorbent was synthesized for the removal of Cu ions in acidic conditions such as those characterizing acid mine drainage (AMD). The synthesis was via a three‐step process involving coating of silica nanoparticles with carbon, oxidation of the carbon layer, and grafting of hexamine to the silica–carbon composites. Transmission electron micrographs showed that the adsorbent comprised spherical particles in the nanometre range although nitrogen sorption isotherms revealed a considerable decrease in particle area as a result of carbonization and hexamine grafting. Spectroscopic analyses confirmed the presence of amine, carboxyl, and hydroxyl groups. On application to Cu‐containing solutions, 52% of the ions were retained by 10 mg of the adsorbent at pH 3. This reaction achieved equilibrium in 45 min and followed pseudo‐second‐order kinetics. Removal with similar adsorbent amounts was higher at pH 5, 7, and 9 (62, 57, and 57%, respectively), and increased with initial Cu concentrations. Adsorption isotherms were fitted by the Freundlich model and the adsorption capacity at pH 3 was determined to be 0.016 mmol g−1. The adsorbent also selectively bound Cu from a multi‐elemental solution indicating that it could be applied for the selective removal of Cu from AMD‐contaminated water. Amine‐functionalized silica–carbon nanocomposites are synthesized by attachment of amino groups to a carbon coating on silica nanoparticles. The nanocomposite trapps >50% of copper ions from acid main drainage contaminated water and exhibited specificity for copper in multi‐element solutions.