Removal of Methyl Orange from Water Using Microalgae: Effect of Operating Parameters, Equilibrium, Kinetic and Thermodynamic Studies

Azo dyes pose a serious problem to water resources and human health. This study aimed to remove methyl orange (MO) from water using living microalgae as an environmentally friendly and economical biosorbent. The experiments were carried out in batch mode under different conditions to investigate the effect of operating parameters on removal efficiency. Equilibrium, kinetic and thermodynamic studies were carried out to understand the elimination mechanism and to determine the nature of the interactions between the MO and the microalgae. A percentage removal of 98.53% was obtained after 45 min of contact time under the optimal conditions of pH 2.5, the temperature of 35 degrees C, microalgae dose of 100 mg L-1, initial concentration of 30 mg L-1, and agitation speed of 260 rpm. Equilibrium and kinetic studies showed that the Langmuir and pseudo-second-order models were the best fit for the experimental data with R-2 > 0.99. The maximum biosorption capacity found was 302.34 mg g(-1). The biosorption occurred on a monolayer surface, and the dominant mechanism was chemisorption. The thermodynamic study showed that the biosorption of MO was endothermic, spontaneous, and favorable. The microalgae also showed their efficiency in removing MO from real waters with percentages of 90.46 +/- 1.6% and 82.21 +/- 2.1% for tap water and raw water dam, respectively. These microalgae can be used successfully for the removal of dyes from water. [GRAPHICS] .