Preparation of COOH-KCC-1/polyamide 6 composite by in situ ring-opening polymerization: synthesis, characterization, and Cd(II) adsorption study

Abstract

A nanocomposite of carboxylic acid-functionalized fibrous silica KCC-1 and polyamide 6 (COOH-KCC-1/PA6 NC) was fabricated through an ultrasonic-assisted in situ ring-opening polymerization approach under an organic solvent-free condition. The presence of abundant functional groups like carboxylic, secondary amine, and ketone in the COOH-KCC-1/PA6 NC structure can make it a good candidate for the adsorption of heavy metals. Accordingly, COOH-KCC-1/PA6 NC was characterized and utilized as an adsorbent for Cd(II) uptake from aqueous media. Crucial adsorption factors, namely pH, adsorbent dosage, Cd(II) initial concentration, and contact time, affecting the removal of Cd(II) were monitored and the optimum adsorption conditions were determined. Isotherm and kinetic investigations were conducted and a non-linear fitting method of experimental data was used to obtain isotherm and kinetic parameters. The experimental maximum adsorption capacity of Cd(II) was found to be 109.2 mg g–1 (pH: 7.0, adsorbent dosage: 0.05 g, initial concentration: 80 mg L–1, time: 240 min, temperature: 25 ℃). The observed adsorption property is due to (1) the uniform distribution of COOH-KCC-1 filler within the PA6 matrix, (2) the presence of abundant adsorption sites like carboxylic acid (−COOH), ketone (–C=O), silanol (Si−OH), and secondary amine (–NH–) in the adsorbent structure, and (3) the structural stability of the adsorbent owing to strong interfacial interactions (physical and chemical bonding) between COOH-KCC-1 and PA6 polymer. Based on the results it can be suggested that the COOH-KCC-1/PA6 NC adsorbent can be handled for the adsorption of Cd(II) from aqueous media.