Analysis of measuring methods of the concentration of methylene blue in the sorption process in fixed-bed column

The wastewater from industry is contaminated with dyes, which should be removed in order to prevent environmental damage. This paper presents a method for removing methylene blue from an aqueous solution using a fixed-bed adsorption process onto sawdust. In the article, the method of continuous measurement of methylene blue concentration in the process of sorption on sawdust was used. The results were compared with the results obtained by the standard method of periodic testing of the dye concentration. Continuous measurement of the dye concentration after the sorption process provides the actual nature of the process and the method offers additional information about the process, as opposed to a periodic test in which the concentration of the ingredient gives only averaged results. The kinetics of the methylene blue sorption process at variable initial dye concentrations are presented. The initial concentration of methylene blue had a significant impact on the process breakthrough curve. The increase in concentration (range of 10–90 mg/dm3) caused the extension of the penetration zone of the dye mass, thus gradually adsorbing itself on the bed. In the study of kinetics, the Bohart–Adams model was the best fit.