Advances in Water Treatment and Enviromental Management

ADSORPTION OF TRIHALOMETHANES ON TO ZEOLITES 185(4) Owing to the low concentrations of THM, accurate and repeatable analyticaltechniques are essential for measurement of solution concentrations.PROCEDUREOrganic-free water is prepared by distillation and then passed through anactivated carbon filter. Purity is verified by gas chromatographic analysis.Standard solutions are then prepared by addition of accurate volumes of THM bymicropipette, with subsequent dilution for lower concentrations in the µg l- 1 range.The adsorbent is prepared by heating in a closed porcelain crucible for 4 hours at400°C immediately prior to each experimental run. A measured weight ofadsorbent is then contacted with a known volume of THM solution of knownconcentration in a screw-topped glass bottle. The bottle is then agitated in aconstant temperature shaker bath for 18 hours, to attain equilibrium. Similarbottles with different concentrations of THM are also shaken, along with controlbottles with no adsorbent. After equilibrium is reached, the concentration of theTHM is measured using a Perkin Elmer 8410 gas chromatograph fitted with a30m×0.25mm J & W fused silica capillary column (DB-5 stationary phase), anelectron capture detector and an HS-6 headspace analyser. The chromatograph iscalibrated with standard solutions of the relevant THM.From a simple mass balance, the quantity of THM taken up by the adsorbent fromthe solution can be calculated for each equilibrium concentration.For the kinetic work, a number of identical bottles containing an equal volume andconcentration of THM solution in contact with a known weight of adsorbent areshaken for 24 hours. Samples are taken from different bottles at progressive timesover the 24 hour period and the concentration of THM measured as before. Controlbottles with no adsorbent are also shaken and analysed. All equilibrium andkinetic experiments are carried out at a water bath temperature of 20°C.RESULTSA typical isotherm for a silicalite/chloroform/water system is shown in Figure 2,for the 0–1000 mg/l equilibrium concentration range. The data obtained is fittedwell by the standard Freundlich isotherm equation:(1)