Influence of pH on the absorption of Cd(II) using cattle manure

Abstract

The presence of cadmium Cd (II) in domestic and industrial wastewater is typical of industrial development and population growth. Its toxicity, its carcinogenic effect and its bioaccumulative nature are dangerous for health. Cattle manure has been chosen as an adsorbent to evaluate its capacity to adsorb Cd (II), from solutions prepared at different concentrations, where pH and contact time are the critical variables of the process. When characterizing cattle manure, most of the functional groups correspond to pectin, cellulose, hemicellulose and lignin, with great capacity to fix ions of Cd (II). The MEB analysis shows signs of pore formation, elemental EDX microanalysis shows that it is composed of 48 % of carbon facilitating that the ions of Cd (II) are attached to the carbon surfaces, the CIC analysis indicates that the surfaces are negatively charged, attracting the ions of the Cd (II) by electrostatic forces. The dosage of cattle manure was 0.0023 g/mL reaching a clearance of around 90 %, making unnecessary an increase in adsorbent. The optimal pH for adsorption of Cd (II) was 3.5 indicating that in an acidic medium a deprotonation of the carboxylic, phenolic and most functional groups of the manure is achieved, with one and two charged oxygen atoms negatively acting as complexing agents, which attract the Cd (II) ions. Finally, with 2 g of adsorbent, 2.3726 mg of Cd (II) of aqueous solutions can be adsorbed.