A novel chitosan–vanadium-titanium-magnetite composite as a superior adsorbent for organic dyes in wastewater

•A novel composite CS-VTM was prepared through one-pot synthesis.•CS-VTM is an ecofriendly adsorbent for effective removal of dye in wastewater.•CS-VTM is demonstrated as the superior adsorbent based on performance evaluation.•The adsorption of CR by CS-VTM was attributed to the formation of hydrogen bonds. In this research, a novel chitosan (CS)–vanadium-titanium-magnetite (VTM) composite was designed and synthesized. The interaction between CS-VTM and Congo red (CR) dye conformed to a pseudo-second-order model to support the potent involvement of chemisorption. The effects of adsorbent dosage, reaction temperature, and initial solution pH on adsorption of CR were investigated. Approximately 99.1% of CR (100 mg/L) was adsorbed at a CS-VTM dose of 2.0 g/L or above, while such a reaction was favored at temperatures of 65 °C and pH of 6.0. Thermodynamically, the adsorption of CR proceeded spontaneously (ΔG