An innovative method of combustion–calcination of a nitrate–ethanol solution to produce magnetic Co0.5Ni0.5Fe2O4 nanoparticles was developed. The calcination temperature and the volume of ethanol were two pivotal elements that determine the properties of the Co0.5Ni0.5Fe2O4 nanoparticles in this study. When the volume of ethanol used was increased from 20 ml to 40 ml, the crystallinity of the Co0.5Ni0.5Fe2O4 nanoparticles increased; further increase of the volume of ethanol decreased the crystallinity. The smallest nanoparticle was obtained using 20 ml ethanol. As the calcination temperature increased from 400 °C to 700 °C, the saturation magnetization of the Co0.5Ni0.5Fe2O4 nanoparticles increased from 12.8 emu g−1 to 30.8 emu g−1. Co0.5Ni0.5Fe2O4 nanoparticles fabricated using 20 ml ethanol at 400 °C were used to study the removal of methyl blue (MB) by adsorption. Experimental data revealed that the adsorption was best described by pseudo-second kinetics. The adsorption isotherm applied the Temkin model, which indicated the presence of a single and multilayer associative mechanism in the adsorption of MB on the Co0.5Ni0.5Fe2O4 nanoparticles. The effect of pH and recycling on the adsorption was measured. At pH values ≥5, the adsorption was high. After eight cycles of use and recycling, the relative removal rate of MB by the Co0.5Ni0.5Fe2O4 nanoparticles was 75% of the initial adsorption value.

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A novel and facile rapid combustion approach was developed for the controllable preparation of small size and easy recovery magnesium-zinc ferrites for methyl blue (MB) removal in dye solution. The effects of prepared criteria of x value, calcination temperature, and the amount of ethanol on the average grain sizes and magnetic property were reviewed. The characterization results displayed that Mg0.5Zn0.5Fe2O4 nanoparticles met the expectations of the experiment at the calcination temperature of 400℃ with absolute ethanol volume of 20 mL, and they were selected to remove MB. The adsorption process belonged to chemical adsorption on the basis of the pseudo-second-order model. The electrochemical characteristics of MB onto the prepared nanoparticles were analyzed by cyclic voltammetry (CV). The influences of pH and cycle times on the removal efficiency were investigated. When the pH went beyond 3, the removal efficiency of MB onto the magnetic Mg0.5Zn0.5Fe2O4 nanoparticles maintained above 99%，the maximum adsorption capacity was 318.18 mg/g. After seven cycles, the relative removal rate of MB remained 96% of the first one.

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Magnetic cobalt-cuprum-zinc ferrites were prepared from anhydrous ethanol using the combustion method, and their structure and properties were characterized using the XRD, SEM, EDS, and VSM techniques, and its formation mechanism was discussed. The magnetic Co0.4Cu0.2Zn0.4Fe2O4 nanoparticles calcined at 400 oC with 25 mL anhydrous ethanol were used for the removal of methyl blue (MB). The results showed that the pseudo-second-order kinetic model best agreed with the adsorption method. In addition, analysis of the adsorption isotherms using the Freundlich, Langmuir, and Temkin models showed that theTemkin model was most consistent with experimental results, which revealed that the adsorption of MB onto the Co0.4Cu0.2Zn0.4Fe2O4 nanoparticles was a multi-molecular layer chemisorption. Further, the influence of pH on the adsorption capacity was evaluated and was highest at pH 11. The cyclability and removal rate of the nanoparticles were explored. The removal rate was approximately 80% after 7 cycles, revealing that the magnetic CoxCuyZn(1-x-y)Fe2O4 nanoparticles are important for wastewater treatment.