Adsorption of cationic dyes and antibiotics from aqueous solution by dopamine-modified peanut husk

Abstract

Dopamine modified peanut husks (PH/DA), a novel adsorbent, were investigated to enhance the adsorption capacity of dyes (neutral red, NR and crystal violet, CV) and fluoroquinolone antibiotics (ofloxacin, OFLX and enoxacin, ENO). Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermo-gravimetric analysis and differential scanning calorimetry (TG-DSC) and Brunauer-Emmett-Teller (BET) method were used to characterize PH and PH/DA. The findings demonstrated that the physical and chemical properties of the peanut husks were changed after dopamine-modification. As for adsorption kinetics, NR adsorption properties were satisfactorily explained by the Elovich model, whereas CV adsorption processes suited to the pseudo-second order model. Both OFLX and ENO followed the pseudo-first order model. Isotherm data showed that CV and ENO conform to the Temkin model while NR and OFLX fitted better to the Langmuir model. The qmax of NR, CV, OFLX and ENO by PH/DA were 52.37, 45.92, 46.57 and 58.40 mg/g at 290 K, respectively, according to Langmuir model. The adsorbent maintained an adsorption efficiency of above 70% even after three adsorption-desorption cycles. These findings proved that PH/DA's successful development offers important insights into the production of sorbents for water treatment based on biomass.