Adsorption Behavior of Cu(II) onto Sludge Particulate Surfaces

Abstract

The influence of culture condition on the production of extracellular polysaccharide, protein, and its effect on the removal of Cu(II) by activated sludge solids is investigated. The surface of sludge particulates grown in low C/N ratio are found to be high in protein but low in polysaccharide content. Both polysaccharide and protein are important to Cu(II) adsorption. The optimal pH values for Cu(II) adsorption are between 5.5 and 6.0. The decrease in Cu(II) adsorption density at pH $>7$ is attributed to the deterioration of biomass. Soluble COD as high as 190.4 mg/L was detected at pH 9.4. The organic ligands will chelate the Cu(II) ions to form soluble organic complexes that are not adsorbable. Surface loading plays an important role in Cu(II) adsorption. The adsorption of Cu(II) onto the sludge particle surface can be described by a modified Langmuir adsorption isotherm that incorporates the effect of proton. It is found that $\left[H^{+}\right]$ behaves as a competitive inhibitor.