Materials and Methods

The coffee husk was collected from coffee processing unit. The husk was washed and boiled to remove colour and impurities. The biomass was then air dried at 105°C for 24 hours and the adsorbent thus processed was used in its original piece size. A stock solution containing 1000 mg/L of Cr (VI) was prepared using potassium dichromate in distilled water. All the chemicals used were of analytical grade. Batch mode experiments were conducted by agitating 1 g of the adsorbent with 100ml of Cr (VI) solution of desired concentration at pH 2.0. The adsorbent was separated using Whatman No.1 filter paper and the supernatant was analysed spectrophotometrically using 1,5 diphenyl carbazide (APHA, 1985). To study the effect of pH, it was varied between 2 and 7 at different initial metal concentrations. The pH was adjusted using 0.1 N NaOH and 0.1 N HCl. The effect of adsorbent dosage was studied by varying the adsorbent from 0.5 to 6 g at various initial metal concentrations at pH 2. The desorption studies were carried out by filtering the Cr(VI) loaded adsorbent from solution, washing gently with distilled water to remove unadsorbed Cr(VI) and  agitating the metal loaded adsorbent with distilled water and varying concentrations of NaOH and HCl. Infrared spectroscopic studies of coffee husk before and after treatment with Cr (VI) was carried out to determine the functional groups responsible for adsorption using a Fourier transform infrared spectrometer (FTIR).