LAUSR

Abstract Diatomite skeletons were decorated by Ni/NiO nanoparticles as novel hybrid materials of enhanced adsorption capacities for Malachite green dye (M.G) and Cr(VI) ions. The characteristic properties of the composite were investigated based on the obtained results of X-ray diffraction, HSEM, HRTEM, FT-IR and pore size distribution analysis. The recorded enhancement in its textural and morphological properties was reflected in an obvious improvement in its adsorption properties. The theoretical qmax values are 350 mg/g and 338 mg/g for M.G and Cr(VI), respectively which are higher than most of the studied diatomite based adsorbents and nickel oxides. The kinetic behavior of Ni/diatomite system for both M.G and Cr(VI) was described based on the suggestion of the pseudo-second-order model and this was supported by its excellent fitness with Elovich model. The equilibrium behaviors can be identified as L-type that impeded strong affinities between the dissolved ions and Ni/diatomite. Additionally, the data fitted mainly with Langmuir model reflecting monolayer adsorption forms within homogenous receptor sites. The adsorption energies for M.G and Cr(VI) were calculated from Dubinin–Radushkevich model to be 5.64 KJ/mol and 6.32 K J/mol, respectively which suggest physisorption nature. The thermodynamic evaluation revealed the uptake of both ions by spontaneous endothermic physical reactions which were reflected in the values for free energy and enthalpy.