Anionic and cationic dyes adsorption on porous poly-melamine-formaldehyde polymer

Liquid phase adsorption is one of the most effective approaches for dye removal from colorant effulent. In this study, we investigated the adsorption behaviors of cationc and anionic dyes on a highly porous adsorbent of poly-melamine-formaldehyde (PMF). Both micropores and mesopores were found in PMF, which supported high specific surface area and pore volume. The maxmium adsorption capaities for methylene blue (MB), methyl violet 2B (MV), methyl orange (MO), orange II sodium salt (OS) and congo red (CR) were 80.8, 113.9, 81.2, 89.3 and 87.5 mg g⁻¹, respectively. Isotherm study showed that the experimental data can be well fitted by Langmuir adsorption model. Kinetic study indicated that the adsorption process followed pseudo-second order kinetic model and both external and intra-particle diffusion were rate-determining steps. Furthermore, dye-exhausted PMF can be regenerated by sulfate radical based advanced oxidation process. After 6 runs, the dye removal percentages for MV and OS were 87.6% and 99.4%, respectively, indicating good stability and reusability of PMF. The main factor contributed to the high adsorption capacity of PMF should be ascribed to its high specific surface area and large pore volume. The advantages of high adsorption capacity and stability made PMF a promising adsorbent for colorant effluent treatment.