Removal of Chromium from Aqueous Stream Using Aluminium Oxide (Synthesized by Simple Precipitation Method) as an Adsorbent

Several studies have been done on discovering the potential of alumina as an adsorbent
to remove heavy metal such as chromium. The purpose of this project is to analyse and
study effect of initial concentration of chromium, contact time between adsorbent and
chromium, and also adsorption kinetics of adsorbent. For this project, to remove
chromium from aqueous stream, the potential of aluminium oxide has been explored.
Aluminium oxide which was used was synthesized by simple precipitation method
where it produced by reaction between aluminium chloride and ammonium hydroxide.
The capability of synthesized aluminium oxide to remove chromium by adsorption was
compared with commercial aluminium oxide. Based on the FESEM result, the pictures
of both morphologies showed that synthesized aluminium oxide had better structure and
more uniform pores than commercial aluminium oxide. Batch adsorption kinetic studies
showed that the adsorption of chromium ion was strongly affected by initial chromium
ion concentration. The amount of chromium ion adsorption on aluminium oxide was
increased with initial chromium ion concentration which was from 20 ppm until 80 ppm.
It also was found that the amount of adsorption was increased with contact time at a
fixed solution pH, amount of adsorbent, initial chromium ion concentration, temperature
and velocity of stirring until the equilibrium concentration was achieved at 180 minutes
(3 hours). A kinetic experiment for adsorption of chromium ion on aluminium oxide was
followed pseudo-second-order kinetics because of higher regression coefficients, R2
which is 0.9776 and theoretical equilibrium sorption capacity, qe (17.361 mg/g) was
more similar with respect to experimental qe (14.5473 mg/g). For adsorption isotherm,
Langmuir adsorption equations reasonably describe the adsorption isotherm within this
chromium ion concentration range. Based on the Langmuir isotherm, R2 is 0.886. In this
project, it was clearly proven that synthesized aluminium oxide was better than
commercial aluminium oxide in terms of the morphology and also the capability of
adsorbing chromium which adsorbed 14.5473 mg/g and 12.7326 mg/g respectively. As
conclusion, considering the high capability of aluminium oxide synthesized by simple
precipitation method as an adsorbent of chromium in aqueous solution via adsorption, it is essential to encourage more researches by manipulating the morphology of aluminium
oxide in order to resolve the pollution of chromium in waste water.