Cationic and anionic dyes are frequently used in industrial sectors and cause many environmental and health problems. Orange peel has the potential to absorb dye as an adsorbent. This study aimed to explore the adsorption of methylene blue (MB) as a cationic dye and methyl orange (MO) as an anionic dye using orange peel (OP) and its modification using cetyltrimethylammonium bromide (CTAB). OP and OP-CTAB biomass materials were characterized using FT-IR (Fourier transform infrared), surface area analysis using BET (Brunauer-Emmett-Teller) and SEM EDX (Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy). Based on the study results, OP has a microporous skin structure and OP-CTAB mesopores. Based on the effect of contact time, it is known that the best adsorption process on MB was to use OP adsorbent with the optimum amount of dye adsorbed produced at 50th minute that was 5.881 ppm, while the best adsorption process on MO was using OP-CTAB adsorbent with the optimum amount of dye was at 50th that was equal to 13.34 ppm. Based on the adsorption kinetics data, the adsorption of MO and MB dyes by OP and OP-CTAB followed the pseudo second order reaction kinetics model. The adsorption of MO and MB by both OP and OP-CTAB followed Langmuir's adsorption isotherm, meaning that the adsorption process in both MO and MB using OP and OP-CTAB appeared on homogeneous surface sites, while there was no interaction between adsorbate molecules and adjacent locations that means the adsorption process only occurred physically.

The development of the textile industry in Indonesia is rapid. It cause serious environmental problems because the dyes used in the textile industry are synthetic that is azo dyes. Azo dyes are non-biodegradable substances that pollute the environment if not processed. One of the azo dyes that is often used in the textile industry is Methyl Orange. Photodegradation is an inexpensive and environmentally friendly method of removing synthetic dyes. This study will discuss the effect of adding orange peel on the characterization of ZnO and the ability to degrade Methyl Orange. The results of the FTIR spectra showed an absorption in the area of 1430-1455 cm-1 that means the orange peel had been impregnated into ZnO and the more ZnO as added on orange peel, it may reduce the number of -OH and CH groups of the ZnO/OP composite. Based on the results of characterization using XRD, it is known that the addition of orange peel into ZnO did not damage the crystal structure and crystal form. The crystal structure of ZnO/OP formed was wurtzite with a hexagonal shape. The results of the characterization using DR-UV showed that the band gap energy of ZnO/OP was smaller than ZnO and the more ZnO was added, the wider the band gap of energy. ZnO/OP with a variation of 1:25 can degrade Methyl Orange more than ZnO that was 73% in 60 minutes.