High Selectivity and Adsorption Capacity for Congo Red Toward Anionic Dyes by Adsorbent: Modified LDH with Hydrochar Made from Nephelium Lappaceum Peel

Abstract

<p>Synthesis of Ni/Al-LDH prepared into Ni/Al-Hc composites using hydrochar from rambutan peel (Hc) and applied as a congo red adsorbent and analyzed based on adsorption selectivity, kinetics, isotherms, adsorption thermodynamics and recycling. The success of Ni/Al-Hc composite preparation was proven by XRD, FT-IR, and BET analysis which showed the unique characteristics of Ni/Al and Hc. The results of the analysis of adsorbent characterization using XRD showed that the peaks in the Ni/Al-Hc composite were similar to typical peaks of Ni/Al appearing around 10.9°(003), 45.5°(018) and hydrochar appearing around 22°(002). The results of the analysis were strengthened by characterization using FT-IR which showed that the Ni/Al-Hc composite had similar spectra with the precursor. BET analysis showed that the Ni/Al-Hc composite had an increase in specific surface area to 11.879 m2/g from 5.845 m2/g after Ni/Al was composited with Hc. The adsorption study showed that the Ni/Al-Hc composite showed selective ability to congo red, and was in equilibrium at 100 minutes with a tendency for adsorption to follow pseudo first order (R2 is closer to 1). The adsorption isotherm shows that the adsorption of Congo red tends to follow Freudlich with the maximum adsorption capacity reaching qm (adsorption capacity) of 246.23 mg/g each using Ni/Al-Hc adsorbent and the adsorption process takes place by physisorption, spontaneous and endothermic. The adsorption regeneration ability is more stable up to the fourth cycle compared to Ni/Al-LDH and Hc with the best desorption reagent using hydrochloric acid.</p>