Comparison of 4-chloro-2-nitrophenol adsorption on single-walled and multi-walled carbon nanotubes

The adsorption characteristics of 4-chloro-2-nitrophenol (4c2np) onto single-walled and multi-walled carbonnanotubes (swcnts and mwcnts) from aqueous solution were investigated with respect to the changes in thecontact time, ph of solution, carbon nanotubes dosage and initial 4c2np concentration. experimental resultsshowed that the adsorption efficiency of 4c2np by carbon nanotubes (both of swcnts and mwcnts) increasedwith increasing the initial 4c2np concentration. the maximum adsorption took place in the ph range of 2–6. thelinear correlation coefficients of different isotherm models were obtained. results revealed that the langmuirisotherm fitted the experimental data better than the others and based on the langmuir model equation,maximum adsorption capacity of 4c2np onto swcnts and mwcnts were 1.44 and 4.42 mg/g, respectively. theobserved changes in the standard gibbs free energy, standard enthalpy and standard entropy showed that theadsorption of 4c2np onto swcnts and mwcnts is spontaneous and exothermic in the temperature range of298–328 k.