JHAZMAT 181-2010-755

Adsorption of methyl orange from aqueous solution onto calcined Lapindo
volcanic mud

In this study, calcined Lapindo volcanic mud (LVM) was used as an adsorbent to remove an anionic dye,
methyl orange (MO), from an aqueous solution by the batch adsorption technique. Various conditions
were evaluated, including initial dye concentration, adsorbent dosage, contact time, solution pH, and
temperature. The adsorption kinetics and equilibrium isotherms of the LVM were studied using pseudofirst-
order and -second-order kinetic equations, as well as the Freundlich and Langmuir models. The
experimental data obtained withLVMfits best to the Langmuir isotherm model and exhibited amaximum
adsorption capacity (qmax) of 333.3mgg−1; the data followed the second-order equation. The intraparticle
diffusion studies revealed that the adsorption rates were not controlled only by the diffusion step. The
thermodynamic parameters, such as the changes in enthalpy, entropy, and Gibbs free energy, showed
that the adsorption is endothermic, random and spontaneous at high temperature. The results indicate
that LVM adsorbsMOefficiently and could be utilized as a low-cost alternative adsorbent for the removal
of anionic dyes in wastewater treatment.