Characteristics Of Trace Pharmaceuticals Adsorption By Different Activated Carbons In Water

The capacities and mechanisms of trace pharmaceuticals adsorption in water by coal carbon (MAC), apricot carbon (XAC) and coconut carbon (YAC) were analyzed by investigating the static adsorption test and continuous adsorption test. Characterization of the ACs, Adsorption equilibrium, isotherms, kinetics and thermodynamics were studied for discussing the adsorption processes and adsorption mechanisms of single and mixed pharmaceuticals in the static adsorption test. Meanwhile the activated carbon columns were used in the continuous adsorption test to verify the practical ability for mixed pharmaceuticals by changing the water flow rate and adding NOMs.The results of the experiments indicated that YAC had the most developed surface areas and functional groups, while the MAC had the most element types. In the static adsorption test of single pharmaceutical, all of the ACs showed the high adsorption capacities for pharmeuticals, which were8.29mg/g(MAC-CBZ),8.19mg/g (XAC-CBZ),8.39mg/g (YAC-CBZ),8.23mg/g (MAC-NAP),6.52mg/g (XAC-NAP) and7.92mg/g (YAC-NAP) respectively, and in mixed pharmaceuticals test the range of the adsorption capacities was7.0-9.0mg/g. The Competition adsorption orders of the pharmaceuticals on the ACs were different, which were ACE>KEP>DCF>CBZ>NAP for MAC, ACE>CBZ>DCF>NAP>KEP for XAC and ACE>DCF>CBZ>KEP>NAP for YAC. Except the adsorptions of CBZ and NAP on MAC fit better with the Freundlich models, all of the adsorption isotherms by the three activated carbons had good agreements with Langmuir models. The adsorption kinetics of pharmaceuticals on MAC, XAC and YAC fit well with pseudo second-order equations and the adsorption rate was influenced by both boundary layer diffusion and intra particle diffusion. Based on the results of thermodynamic calculation, the adsorption of pharmaceuticals by MAC, XAC and YAC could be due to chemical adsorption and physical adsorption as well, and the former being a larger contributor. In addition, the pharmaceutical adsorptions on the three materials were shown to be spontaneous processes. While in the single solutions,△H of CBZ were-3.10kJ/mol (MAC),-3.05kJ/mol (XAC),-3.02kJ/mol (YAC), and NAP were19.72kJ/mol (MAC),15.41kJ/mol (XAC),18.52kJ/mol (YAC) respectively, which meaned the high tempreture was adverse to the CBZ and benefit to the NAP. In the mixed solution the thermodynamic process depended on the value of△H. The results of continuous adsorption test stated that the activated carbon column could remove the pharmaceuticals in water effectively.