In this thesis, two catalytic and absorption applications of magnetic nanoparticles MnCoFe₂O₄@PEG were investigated. At first, the nanoparticles were synthesized with a green and easy method and were identified by XRD, FESEM, EDX, TEM, TGA and VSM analyses. Then, in the first part of the thesis, the catalytic power of these nanoparticles for the synthesis of hexahydroquinolines and benzopyrans from the three-component reaction between aromatic aldehyde, malononitril, dimedon or 5,5-dimethyl-3-(phenylamino)cyclohex-2-en-1-one, was investigated. Short reaction time, high efficiency, easy purification of derivatives and also easy separation of magnetic nanocatalyst by the external magnetic field were highlights for this work. Also, in the second part of the work, the adsorption power of these nanoparticles was investigated and two ions of copper (II) and iron (III) were chosen for this purpose. According to the obtained results, in optimal conditions, the removal efficiency of copper (II) and iron (III) was 99.95% and 99.99% respectively. Also, the recovery and reuse of synthesized magnetic nanoparticles MnCoFe₂O₄@PEG in both catalytic and absorption processes were investigated during four cycles. Finally, according to the results of this research, as can see the nanoparticles MnCoFe₂O₄@PEG has provided an acceptable performance as a catalyst in the synthesis reaction of hexahydroquinolines and benzopyrans compounds and also as a nanoabsorbent for the removal of heavy metals copper (II) and iron (III).