Synthesis, characterization, and application of magnetized Azadirachta indica sawdust as a novel adsorbent: kinetic, and isotherm studies in removing methylene blue as a model dye

The adsorption properties of magnetically modified Azadirachta indica sawdust (MAIS) on cationic methylene blue (MB) dye were studied. A number of conventional and modern analytical methods, viz., SEM/EDXS, TEM/SAED, BET, XRD, Raman, FTIR, TGA-DTG /DTA, VSM, and point of zero charge (Pozc) were used for characterization of the developed adsorbent. Batch adsorption experiments were conducted to determine how adsorption was affected by various factors like adsorbate/adsorbent contact time, medium pH, adsorbent dosage, temperature, and starting dye concentration. The experimental data were analyzed in the light of various isotherm and kinetic models. The data accompanying the adsorption of MB by MAIS were found to be best obeyed by Langmuir isotherm and Pseudo-second-order kinetic models. The maximum adsorption capacity for the Langmuir monolayer coverage was calculated to be 169.491 mg/g. The remediation of MB was found to be thermodynamically spontaneous, endothermic, and accompanied by an entropy increase. Desorption experiments suggested that HCl is an effective desorbing agent, and MAIS can be reused successfully for up to seven repeated adsorption-desorption cycles. The combined benefit of facile synthesis, low-cost, outstanding binding ability for decontaminating dye, easy separability from aqueous media, and reusability suggest that the MAIS is a cost-effective and efficient novel adsorbent.