Abstract
Herein, low-cost diatomite (DE) and bentonite (BE) materials were surface modified with Ni–Fe layered double hydroxide (LDHs) (represented as NFD and NFB respectively), using a simple co-precipitation procedure for the removal of methyl orange (MO) dye from water. The adsorbents of both before and after MO adsorption have been studied by XRD, N2 adsorption-desorption isotherm, FTIR, FESEM-EDX and XPS characterization. The zeta potential analysis was used to observe the surface charge of adsorbents within the pH ranges of 4–10. The MO removal efficiency was significantly improved after LDHs modification, showing a 94.7% and 92.6% efficiency for NFD and NFB at pH 6, respectively. Whereas bare DE and BE have shown removal efficiency of 15.5% and 4.9% respectively. The maximum adsorption capacities of NFD and NFB using the Langmuir isotherm model were found to be 246.9 mgg−1 and 215.9 mgg−1 respectively. The designed NFD showed high selectivity towards anionic-based dyes from water and also the effect of salts shows the dye removal percentage was increased and decreased for the addition of Na2SO4 and NaCl, respectively. The reusability of NFD and NFB have been studied for a maximum of five cycles and they can remove MO up to four cycles. Therefore, the designed adsorbents can be very effective towards the removal of MO from water and they may be useful for dye-based wastewater treatment.
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•Low-cost diatomite and bentonites were modified with Ni–Fe LDH, for the removal of methyl orange.•Adsorption capacities of composite materials were significantly improved.•Selective removal of anionic dyes and the effect of salts on adsorption were studied.•The adsorbents could be recycled up to five times, which shows decent removal capacity even upon recycling.•Electrostatic interactions and hydrogen bonding are prominent in dye adsorption mechanism.