Equilibrium and kinetics studies for the adsorption of Basic Red 46 on nickel oxide nanoparticles-modified diatomite in aqueous solutions

• The nanoparticles of NiO were synthesized by adding NiSO4 and NaOH to the solution.
• Diatomite was modified with nickel oxide nanoparticles to enhance its efficiency.
• Nickel oxide nanoparticles-modified diatomite is used for the adsorption of BR46.
• The structure of diatomite changed from sheet to sphere after modification process.

The nickel oxide nanoparticles-modified diatomite (NONMD) as a low-cost adsorbent was investigated for the removal of C.I. Basic Red 46 (BR46) from aqueous solution. Various physico-chemical parameters were studied such as solution pH, adsorbent dosage, adsorbent size, initial dye concentration, temperature, contact time and salt (NaCl, NaHCO3 and Na2SO4). The mean size and the surface morphology of the adsorbent were characterized by SEM, BET, FTIR, XRD, EDX and elemental analysis. The maximum percentage of BR46 dye removal from aqueous solution was 99.48% (124.35 mg/g) when 0.005 g of NONMD was applied at pH 8, temperature 25 ± 1 °C, agitation speed of 200 rpm, initial dye concentration of 25 mg/L, and a mixing time of 60 min. Furthermore, under the same conditions, the maximum adsorption of dye on raw diatomite was 84.49% (105.61 mg/g). The experimental data showed that the adsorption of dye on raw diatomite follows the Langmuir model, but its adsorption on modified diatomite followed the BET model. The kinetics results were found to conform well to pseudo-second order kinetics model with good correlation. Thus, this study demonstrated that the NONMD could be used as a low-cost natural adsorbent for removal of BR46 from aqueous solution.