Development of a magnetic orange seed/Fe3O4 composite for the removal of methylene blue and crystal violet from aqueous media

Abundant quantities of orange waste are produced annually, and their use for sewage treatment is admirable. The orange seeds powder was modified with Fe 3 O 4 and applied for eliminating methylene blue and crystal violet dyes. The active surface of orange seeds powder and orange seeds powder/Fe 3 O 4 was determined to be 4.02 and 69 m 2 /g, respectively. The magnetic property of orange seeds powder/Fe 3 O 4 was such that it was easily separated from the purified water with a simple magnet. The maximum removal by orange seeds powder/Fe 3 O 4 was quantified to be 98.86% (for crystal violet) and 99.27% (for methylene blue), respectively. The highest efficiency for orange seeds powder/Fe 3 O 4 was recorded at pH = 8, dye concentration of 10 mg/L, and adsorber mass of 1 g/L. The pseudo-secondary kinetic model was suitable for describing the adsorption data. Based on Gibbs free energy and enthalpy, the process was spontaneous and endothermic. Investigating the adsorption–desorption and industrial wastewater purification ability showed that the adsorbers in question can be used in the removal process of crystal violet and methylene blue in more than 5 steps. The findings showed that orange seed powder and Fe 3 O 4 particles can be suitable adsorbers for removing colored pollutants from aqueous solutions.