Background, Aim and Scope:
Manganese oxides are widely known as highly efficient heavy metal adsorbing materials. Therefore the use of natural materials containing Mn-oxihydroxides for the treatment of drinking water containing heavy metals in developing countries could be a cheap but nevertheless practical method. In the Karst area of Gunung Sewu, Java, Indonesia, people use the underground water resources as drinking water, which are endangered by heavy metal pollution. Local household filters have been considered for heavy metal elimination, to guarantee high quality drinking water from the Karst water. The aim of this study was to examine the suitability of mineral deposits containing Mn-oxihydroxides found in the Karst cave Bribin as filter material.
Materials and Methods:
Batch experiments were performed with the selected divalent cations Cd2+, Zn2+ and Ni2+ to test the adsorption efficiency of the Mn-rich deposits from Bribin to immobilize dissolved heavy metals.
Results:
Maximum adsorption capacities of 285 µmol/g for Cd2+, 217 µmol/g for Zn2+, and 178 µmol/g for Ni2+ were achieved after 24 h reaction time. These values are higher than literature values of Ni, Cd and Zn adsorption to other synthetic and natural manganese oxides.
Discussion:
Kinetic data from the batch experiments suggest that metal fixation occur in two steps; fast surface adsorption followed by a slower intercalation of the metal ions into the Mn-oxihydroxide lattice. Multi-element analysis of blank samples and samples under competitive conditions implies no desorption of metals from Mn-oxihydroxides.
Conclusions:
The sorption kinetics and capacities achieved in these experiments suggest that Mn-oxihydroxides from Bribin could be an effective filter material for drinking water purification.
Recommendations and
Perspectives:
Nevertheless, reducing conditions in a filter system must be avoided to prevent Mn-oxides being reductively dissolved and the sorbed heavy metals mobilized.
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