Removal of dissolved organic compounds in fixed-bed columns: Evaluation oflow-rank coal adsorbents

Characterisation of a range of Victorian low-rank coal (VLRC) based and com mercial adsorbents under continuous flow conditions was conducted in down f low fixed-bed columns. The effect of bed depth, hydraulic loading and initi al concentration of the adsorbate 4-nitrophenol (4-NP) was studied. Predict ion of the performance of the columns using bed-depth/service time analysis showed good agreement with the experimental results. The VLRC-based activa ted carbons gave lower service times for removal of 4-NP compared with the coconut-based commercial activated carbon Picactif. However, they showed co mparable efficiency in terms of bed volumes treated and carbon usage rate ( CUR). The VLRC-activated power station char (APSC) showed the low est CUR o f 0.57 g/L in comparison with 0.62 and 3.61 g/L exhibited by the commercial carbons Picactif and Hydraffin, respectively. The power station char (PSC) and Auschar gave poor CUR of 11.23 and 75.36 g/L, respectively. Three adso rbents H ere evaluated for the removal of natural organic matter (NOM) from aqueous solution. The breakthrough behaviour indicated that the pore size distribution of the adsorbents is an important physical characteristic for the adsorption of the NOM. There was a non-adsorbable fraction of the NOM t hat was a function of the type of adsorbent. In the presence of NOM, Picact if gave longer service time for the removal of 4-NP compared with APSC, con sistent with the trend obtained in the absence of NOM. However, lower break through times (at 10% C-0) of 44 and 47% were obtained for APSC and Picacti f, respectively. Further removal (35%) of 4-NP was achieved over extended o peration of the beds, however more frequent backwashing was required as a r esult of the biological growth exhibited in the presence of NOM. (C) 2001 E lsevier Science Ltd. All rights reserved.