Efficient Removal of Methyl Orange and Alizarin Red S from pH-Unregulated Aqueous Solution by the Catechol–Amine Resin Composite Using Hydrocellulose as Precursor

We report a novel composite absorbent prepared by the simple method that catechol-amine resin coats the hydrocellulose based on the adhesion property like polydopamine. The composite which contains many chelating groups on its surface was characterized by scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), etc. The obtained adsorbents were investigated to remove Methyl Orange (MO) and Alizarin Red S (AR) from pH-unregulated aqueous system by batch experiments, including the affected factors of adsorbent dosage, contact time, initial concentration, and temperature. Results showed the adsorption processes belonged to the chemisorption and exhibited a spontaneous and endothermic nature. Besides, the removal performances fitted with the Langmuir isotherm model and pseudo-second order kinetic model very well. The maximum adsorption amounts of MO and AR were 189.39 and 284.09 mg/g at 303 K, respectively. The difference about adsorption amounts may be caused by the strong effect of π–π conjugation and hydrogen bonding between adsorbent and AR. Furthermore, the adsorption processes exhibited a spontaneous and endothermic nature. The recycling test indicated that the adsorbent stayed stable for the removal of both dyes by desorbed three times. Accordingly, the adsorbent with high adsorption capacity and rapid removal rate should be a promising material for the removal of anionic dyes from sewage.