Abstract

To alleviate the environmental problem associated with rare earth wastewater, this research applied waste orange peel (OP) for the adsorption of La(III) and Y(III) from aqueous solution. The adsorption properties of orange peel are characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), and the participation of hydroxyl and other oxygen-containing groups that promote the physical-chemical interaction is verified. Batch adsorption results suggest that orange peel possesses a satisfactory adsorption performance for La(III) and Y(III). The optimal adsorption conditions were obtained at pH of 6, temperature of 40°C, appropriate dosage of 2 g/L and 3 g/L, contact time of 30 min, and initial ion concentration of 32 mg/L. Under the same condition, adsorption performance of La(III) is better than that of Y(III). The experimental data is well fitted by the Langmuir isotherm model with [Formula: see text] and the minimum standard error values. Equilibrium results show that Langmuir monolayer adsorption capacity of La(III) and Y(III) onto orange peel is up to 37.61 and 31.10 mg/g. The fitting results of kinetics prove that the adsorption process of La(III) and Y(III) follows the pseudosecond-order model. Thus, natural orange peel as a recyclable biosorbent has potential economic and applicative benefits to remove La(III) and Y(III) from aqueous solutions.

Highlights

  • Ion-adsorbed earth ore is one of the most crucial mineral resources in the world

  • The phenomenon reveals that the pore structure of orange peel (OP) is conducive to physical adsorption, and the charge aggregation of particle surface can be illustrated by the outersphere mutual acting and the surface nucleation of rare earth elements (REEs) microcrystals in the adsorption process [9, 28]

  • The study indicates that OP as an economical adsorbent in practice is a good alternative for costly adsorbents

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Summary

Introduction

Ion-adsorbed earth ore is one of the most crucial mineral resources in the world. It is increasingly frequent to generate massive volumes of rare earth wastewater on account of continuous mining and smelting [1, 2]. Contaminated water from a mine in southern Jiangxi was measured that contained various rare earth elements (REEs), especially the higher concentrations of lanthanum and yttrium [3]. For the porous surface and abundant adsorption functional groups with strong binding ability containing a carboxyl group, hydroxyl group, and amide group [9], orange peel (OP) is an exemplary candidate to deploy the adsorption technology for the mitigation of wastewater pollution; their biosorption studies have been mainly focused on heavy metals [10], organic drug [11], toxic oxyanions [12], and dyeing [13] wastewater. The majority of studies have focused on modifying with OP to improve the adsorption capacity, and the modification methods mainly include acid [16], alkali [17], salt [18], structure [19], carbonization [20], organic solvents [21], and compound modification [22].

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