Removal of Chromium, Iron and Manganese from contaminated waters using cryogels as adsorbent

Abstract

The aim of this study was to remove ions chromium (Cr³⁺), iron (Fe³⁺) and manganese (Mn²⁺) from contaminated waters using polyacriamine gel macropores (MPAAG) called cryogels or hydrogel as adsorbent material. The cryogel MPAAG was prepared at a concentration of 7,5 % (w/v), the polymerization of which was performed at -12 ^oC for 1 hours. Amine and carboxyl ligand groups such as tris (2aminoethyl) amine (TREN) followed by bromoacetic acid (BA) were added. Cr³⁺, Fe³⁺ y Mn²⁺ ions solutions at a concentration of 74 mg/L, 24 mg/L and 27 mg/L respectively were in contact with the adsorbent (MPAAG-TBA) adjusted to pH 2, 3 and 5 to Cr³⁺, pH 3 y 5 to Fe³⁺ and pH 3, 5 and 7 to Mn²⁺; the solution was shaken at 200 rpm for 3 hours; aliquots of 10 ml were taken at 5, 10, 30, 60, 120 and 180 minutes. The concentration of metals was determined using the Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) technique. The maximum adsorption capacity Cr³⁺ was determined (7.52 mg/g) at pH 3, Fe³⁺ (1.13 mg/g) at pH 5 and Mn²⁺ (1.51 mg/g) at pH 7 was determinated using Langmuir model. The results of adsorption isotherm of metallic ions on MPAAG-TBA were better represented by the Freundlich model, demonstrating an adsorption in multilayers of a heterogeneous surface. Also, the separation factor was equal to one, indicating a linear adsorption based on the Langmuir isotherm model. The results indicate that the cryogel MPAAG-TBA has chelating properties for the removal of Cr³⁺, Fe³⁺ and Mn²⁺ in contaminated waters.