Textural and surface chemical characteristics of activated carbons prepared from cattle manure compost

Two activated carbons (ACs) prepared from cattle manure compost (CMC) by ZnCl2 activation were selected and out-gassed in a helium flow at various temperatures for 2 h. The pore structure and surface chemical properties of the two selected ACs and their out-gassing treated ACs were characterized using N2 adsorption–desorption, elements analysis, SEM and Boehm titration. A basic dye, methylene blue (MB), was chosen as an adsorbate to investigate the adsorption capacity for organic contaminant onto the activated carbons. It was found that the out-gassing treatment at 400 °C had little effect on the textural characteristics of the carbons but significantly changed the surface chemical properties such as surface functional groups concentration, pH and pHPZC. The CMC-based activated carbons exhibited excellent performance for MB adsorption due to their high surface area, large mesopore volume and high nitrogen content. The kinetics of MB adsorption onto the activated carbons followed a pseudo-second-order equation, and the equilibrium data agreed well with the Langmuir model under the experimental conditions. The highest adsorption rate constant of kad and the largest adsorption capacity of qm were found be 1.44 × 10−4 g/mg min and 519 mg/g, respectively. The results suggested that the CMC-based activated carbons were effective adsorbents for the removal of methylene blue from aqueous solution.