| With the development of rare earth materials,the demand for ionic rare earth resources is increasing steeply.However,in the process of ionic rare earth mining,a large amount of wastewater is diffused,resulting in the intensification of water and soil pollution in and around the mining area,great waste of rare earth resources,and serious loss of national property.Hence,it is of great significance to study the treatment of rare earth wastewater.Based on the potential application of biomass and clay in the treatment of rare earth wastewater,taking the organic biomass-orange peel and inorganic clay-montmorillonite as adsorption raw materials,the batch single-factor adsorption experiments were conducted by preparing La(Ⅲ)and Y(Ⅲ)ion solutions.Combined with characterization analysis,the effects of raw material types and modification conditions on the physicochemical properties and adsorption effects of adsorption materials were compared to determine the environmental factors when the adsorption performance was optimal.The isothermal adsorption,kinetic and thermodynamic models were fitted to reveal the adsorption behavior and mechanism of adsorption materials,and the main conclusions are as follows:(1)The optimal adsorption conditions for La(Ⅲ)and Y(Ⅲ)ions adsorption by orange peel(OP)were initial ion concentration 32 mg/L,40 °C,p H value of 6,contact time of 30 min,and OP dosage of 2 g/L and 3 g/L,respectively.Under the same conditions,the performance of La(Ⅲ)adsorption by orange peel was better than that of Y(Ⅲ)adsorption.In addition,the experimental data fitted best with the Langmuir isothermal model,and the Langmuir monolayer adsorption amounts reached 37.61 mg/g and 31.10 mg/g for La(Ⅲ)and Y(Ⅲ),respectively.The kinetic fitting results suggested that the process was in accordance with the pseudo-secondorder model.Characterization analysis confirmed that oxygen-containing groups such as hydroxyl and carboxyl in the main components of orange peel participate in and promote the physicochemical interaction during the adsorption process of La(Ⅲ)and Y(Ⅲ).(2)In the pyrolysis temperature range of 200 ℃～600 ℃,the higher the temperature of preparation,the stronger the OPB alkalinity,and the evident the adsorption effect in acid solution.OPB has a better adsorption capacity to La(Ⅲ),and that amount can be increased to55.57 mg/g,the dosage is only 1 g/L.Combining characterization and thermodynamic analysis,it was found that the pore structure and functional groups on the OPB surface play an important role,resulting from physical adsorption enhancing.Additionally,the greater the ion concentration(<100 mg/L)and temperature(<45 °C)of the solution,the more violent the heatabsorbing spontaneous reaction of OPB on La(Ⅲ)and Y(Ⅲ),and the better the adsorption effect.Similar to OP adsorption,the adsorption behavior of OPB on La(Ⅲ)and Y(Ⅲ)can be accurately described with the Langmuir and quasi-secondary kinetic models.(3)After carbonization(OPB400-MT)and saponification(MOP-MT),the adsorption capacity of OP and montmorillonite composites for La(Ⅲ)and Y(Ⅲ)reached 66.03 mg/g,35.14 mg/g,and 70.1852 mg/g,40.27 mg/g,respectively.And the influence of single environmental factors on the adsorption effect became smaller,which means improved the stability of adsorbents.The results showed that the experimental data can be well fitted by Langmuir,Freundlich and D-R models,and the quasi-second-order kinetic model can perfectly describe the adsorption process of composites for La(Ⅲ)and Y(Ⅲ).In the adsorption process of La(Ⅲ)and Y(Ⅲ),electrostatic attraction,ion exchange and complexation work together,chemisorption plays a major role,and the intraparticle diffusion step controls the adsorption of OPB400-MT more significantly.The increased adsorption sites and negative charges on the montmorillonite bound to orange peel greatly enhance the adsorption effect.Meanwhile,the rising temperature promotes the adsorption performance by enhancing the adsorption driving. |
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