Evaluation of Victorian low rank coal-based adsorbents for the removal of organic compounds from aqueous systems

Three activated carbons and two chars made from low rank coal were evaluate d in terms of their ability to remove the organic compound 4-nitrophenol (4 -NP) and natural organic matter (NOM) from aqueous systems. The adsorption equilibrium capacities of all adsorbents for 4-NP correlated with the micro pore area of the adsorbents. Adsorption rates showed improved removal with decreasing particle size and higher carbon mass loadings. A pseudo first or der model was used to fit the kinetic data, with a correlation coefficient of 0.995-0.999 for all systems. The adsorption capacity for NOM, as measured by UV-absorbing DOG, correlate d well with the pore volume and pore surface areas for pores with diameters in the range 2.7-21 nm. The trend in the adsorption capacities and removal rates of the adsorbents for NOM provided evidence that the pore size distr ibution is one of the most important physical characteristics of activated carbon for the adsorption of NOM. The performance of activated low rank coal based materials was comparable t o a high quality coconut-based commercial carbon in batch systems. Although the non-activated char adsorbents gave poor performance, they have potenti al for use in applications where poor performance can be outweighed by lowe r cost. (C) 2000 Elsevier Science Ltd. All rights reserved.