Removal of basic dye (methylene blue) from aqueous solution using zeolite synthesized from electrolytic manganese residue

• Zeolite was first synthesized from electrolytic manganese residue (EMR).
• EMR derived zeolite proved to be an efficient adsorbent for methylene blue.
• A novel conversion route for the utilization of EMR was proposed.
• The adsorption mechanism and kinetics were systematically studied.
• The adsorption was found to be spontaneous and endothermic in nature.

The zeolite synthesized from electrolytic manganese residue (EMRZ) was investigated as adsorbents to remove methylene blue (MB), a cationic dye, from aqueous solutions. The effects of various experimental parameters, such as contact time, initial MB concentration, temperature and pH on the adsorption capacity were investigated. The results showed that the adsorption behavior of EMRZ was greatly affected by pH and temperature. And higher solution pH and temperature resulted in higher adsorption capacity of MB. The experimental data were also analyzed by the Langmuir and Freundlich models of adsorption. The adsorption of MB onto EMRZ agrees well with the Langmuir isotherm and the thermodynamic parameters such ΔH, ΔS and ΔG were determined to be +37.46 kJ mol−1, +201.03 J mol−1 K−1, −23.45 to −25.46 kJ mol−1, respectively, showing adsorption to be an endothermic yet spontaneous process. Moreover, pseudo-first-order and pseudo-second-order models were considered to evaluate the rate parameters. The adsorption process could be described well by pseudo-second-order model, with an activation energy of +13.71 kJ mol−1. These results indicate that the synthesized EMRZ is a promising and low-cost adsorbent for removing dyes from wastewater due to the high adsorption capacity.