Removal of Orange G and Rhodamine B dyes from aqueous system using hydrothermally synthesized zinc oxide loaded activated carbon (ZnO-AC)

- Hydrothermally synthesized ZnO-AC was effective for both acidic and basic dyes.
- Adsorption capacity (qmax) for OG and Rh-B was 153.8 and 128.2 mg/g, respectively.
- Langmuir isotherm and pseudo-second order were best fitted to the data.

This study reports the synthesis of zinc oxide loaded activated carbon (ZnO-AC) using hydrothermal method and its use to remove organic dyes [Orange G (OG) and Rhodamine B (Rh-B)] from the aqueous system under varying process conditions. ZnO-AC nanoparticles were characterized using XRD, SEM, EDX, DLS, and FTIR. The Langmuir adsorption model was best fitted to the experimental data for both the dyes. Langmuir adsorption capacity (qmax) for OG and Rh-B was 153.8 and 128.2 mg/g, respectively. The rate of adsorption was investigated by various models namely pseudo-first-order, pseudo-second-order and intraparticle diffusion model. Rate mechanism was described by pseudo-second-order model for both the dyes. Thermodynamic studies suggested that removal of Rh-B onto ZnO-AC was endothermic up to a temperature of 40 °C while OG removal decreased with increase in temperature. Negative values of ΔG0 for adsorption of dyes suggested spontaneous adsorption processes.

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