PMC:4764609 / 14435-15850 JSONTXT

{"target":"http://pubannotation.org/docs/sourcedb/PMC/sourceid/4764609","sourcedb":"PMC","sourceid":"4764609","source_url":"https://www.ncbi.nlm.nih.gov/pmc/4764609","text":"Effect of contact time\nThe results showed that the percentage removal of copper increased briskly up to 60 min reaching 93.925 % (Fig. 1a). Beyond 60 min, the % of adsorption remained the same indicating the attainment of equilibrium conditions. Equilibrium indicates utilization of the more readily available adsorbing sites especially the carboxyl and the amino groups present on the DNES–CH composite surface. Initial rates of sorption are faster due to the availability of adequate vacant surface binding sites and the vanderwaal forces of attraction between the adsorbate and the adsorbent. With the advancement of time, sorption becomes gradually tapered due to repulsive forces between the solute molecules of the solid and the bulk phases; consequently, the remaining vacant binding sites fail to bind with the metals (Srivastava et al. 2014). The reported contact time of 150 min for removal of copper by chick egg shells by packed-bed sorption (Nabil and Sameer 2009) is much higher than the optimum contact time of 60 min for the composite in the present study.\nFig. 1 a Effect of contact time on % adsorption of copper. b Effect of pH on % adsorption and metal uptake of copper. c Effect of initial metal concentration on % adsorption and metal uptake of copper. d Effect of adsorbent dosage on % adsorption and metal uptake of copper. e Effect of temperature on % adsorption and metal uptake of copper","divisions":[{"label":"title","span":{"begin":0,"end":22}},{"label":"label","span":{"begin":1073,"end":1079}}],"tracks":[]}