Design of a new technique based on combination of ultrasound waves via magnetite solid phase and cloud point microextraction for determination of Cr(III) ions

•Combination of ultrasound waves via magnetite solid phase and cloud point microextraction as new method for determination of Cr(III) ions.•Synthesis of new magnetite sorbent based chitosan grafted with graphene oxide and hybrid with Zn: Fe2O4.•Spectrophotometric detection of Cr(III) after complexation via congo red. In this work, we focused on development of a new techniques by coupling of ultrasound irradiation, cloud point method and magnetite solid phase microextraction for the extraction and preconcentration of Cr(III) ions from aqueous solutions. In order to reduce cost and improve practicability of proposed process a new efficient and regenerable magnetite sorbent (functionalized chitosan grafted-amino graphene oxide (GO) decorated by zinc ferrite nanoparticles (CS-GO-Zn: Fe2O4)) was synthesized through hydrothermal method and then characterized by FT-IR, FE-SEM, EDS and XRD analysis. Effect of initial sample volume and type, volume and concentration of eluent on the ER%Cr(III) were investigated and optimized using one at a time method. Correlation between the main and interaction effects of other operational parameters such as Cr(III) ion concentration, CS-GO-Zn: Fe2O4 mass, sonication time, pH and solution temperature on the ER%Cr(III) were investigated and optimized by central composite design coupled with desirability function approach. The results revealed that there were significant effects for most investigated terms on the ER%Cr(III) and maximum ER% of 88.09% was obtained in desirability value of 1.0. This maximum efficiency was obtained at 0.035µg/mL Cr(III) ion concentration, 40.16°C temperature, 0.016g of CS-GO-Zn: Fe2O4, pH 6.36 and 9.20min sonication time. In addition, under the optimal conditions the linear range, limit of detection, enrichment factor and relative standard deviation were found to be 0.02–4.4µg/mL, 0.002µg/mL, 23.23 and 1.68% respectively. Finally, the method was successfully applied to the separation and preconcentration of Cr(III) ion from tap, river and mineral waters.