The biomass was collected from the local tree bark and first of all washed with distilled water
and then dried for 48 hours in an oven at 500C. Then the bark material was grinded into a
very fine particle size. The adsorbent material is modified with 0.1 M H2SO4 and 6.5 ml of
39% HCHO. The mixture was stirred at 500C for 2 hour and filtered through a glass funnel.
The product material so formed was then washed with deionized water till the pH of the
filtrate reached between 5 - 6. The treatment with formaldehyde under temperature and acidic
condition polymerizes and insolubilizes the tannin and pectin compounds. Batch biosorption
studies were carried out using a certain amount of modified bark and 50 ml of the solution of
Cr (VI) in a conical flask with constant shaking. The following operating conditions such as
pH, adsorbent amount, contact time, metal ion concentration and effect of temperature were
investigated.