Abstract
An anionic adsorbent was prepared by grafting citrate onto pomelo peel (PPL) to remove methylene blue (MB) from aqueous solution. The PPL and modified pomelo peel (MPPL) were analyzed by Fourier transform infrared spectroscopy (FTIR) and observed by scanning electron microscopy (SEM). The effects of dye concentration, contact time, and pH on adsorption were studied. The FTIR results confirmed that the carboxyl groups were successfully bound to cellulose molecules in PPL via modification with citrate. SEM indicated that the surface of PPL became clean and the porous structure was well maintained after modification. The adsorption capacities of MB onto PPL and MPPL were 81.7 mg/g and 199.2 mg/g, respectively, thus indicating that the addition of anionic groups significantly improved the adsorption performance. The increase in the initial dye concentration and pH of the dye solution promoted the adsorption process. The adsorption equilibrium on MPPL required approximately 3 h. The adsorption of MB on MPPL was well described by a pseudo-second order kinetic model and Langmuir isotherm model. The thermodynamic parameters indicated spontaneous and exothermic adsorption. This study suggests that PPL modified with citrate can be used as a sustainable adsorbent in wastewater purification.
Highlights
In the past several decades, dye has been commonly used in the textile, paint, paper, food, leather, and rubber industries [1]
The results indicated that the modification effectively improved the adsorption performance of pomelo peel (PPL), owing to the introduction of carboxylic anions, which improved the adsorption performance of PPL, owing to the introduction of carboxylic anions, which interacted with cationic dye molecules via electrostatic attraction
The negative ∆H◦ indicated that the adsorption process was exothermic, and increasing the temperature would not favor the adsorption of Methylene blue (MB) on modified pomelo peel (MPPL)
Summary
In the past several decades, dye has been commonly used in the textile, paint, paper, food, leather, and rubber industries [1]. 22ofof1111 of biomass wastes can become active sites for the adsorption of dye wastewater [15,16,17]. In many in the molecular structure of biomass wastes can become active sites for the adsorption of dye studies, the adsorption capacity of the biomass itself has been investigated in dye wastewater. Chemical modification can markedly improve the adsorption capacity of some biomass in dye wastewater. High consumption of pomelo produces large amounts of pomelo peels (PPLs), which are disposed of as waste, resulting in inefficient resource and land use. PPL has been directly used as an adsorbent for purification of oil pollution [19] and dyes [20].
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