Effects of Some Experimental Variables on the Adsorption of Hexavalent Chromium from Aqueous Solution Using Red Mangrove (Rhizophora mangle)

Abstract

The effects of particle size, pH and initial concentration of adsorbate
on the adsorption of hexavalent chromium from aqueous solution
using red mangrove biomass (leaves, bark and root) as adsorbents
were investigated by batch adsorption method. The main objective
was to analyze and report the efficiency of red mangrove leaves, bark
and root in removing hexavalent chromium ion from aqueous solution
in terms of particle size of adsorbent, initial concentration of
hexavalent chromium and pH of solution. The adsorption was found
to be dependent on all the variables. The percentage hexavalent
chromium adsorbed decreased as particle size of red mangrove
biomass powder, initial concentration of hexavalent chromium and
pH of solution increased. Maximum adsorptions were observed at
particle size of 150????m, initial concentration of 20ppm and pH of 2.
Minimum adsorptions were obtained at particle size of 2000????m, initial
concentration of 100ppm and pH of 9. However, results show greater
adsorption by red mangrove root and leaves than the bark, suggesting
that red mangrove biomass especially the root and leaves can be used
as low-cost adsorbent for the removal of hexavalent chromium ion
from aqueous solution. Protonation/deprotonation and surface
association have been mentioned as possible reaction pathways in the
pH and in the non-pH-controlled adsorptions.