Preparation Of The Porous Carbon Material Based On Quinoa Straw And Its Adsorption Performance For RhB

It was reported that hundred tons of printing and dyeing wastewater was discharged each year in China,which seriously threats the environment and the human health.Therefore,the development of advanced materials or technologies has attracted wide attention.It is expected that the printing and dyeing wastewater could be effectively,conveniently,and cheaply purified.Because of its unique advantages,adsorption has been considered as one of the most important methods for purifying wastewater.Carbon-based materials are usually used as the adsorbents in the adsorption processes.As a result,the porous carbon-based materials with the advantages of higher performances,lower price,good reuseability were highly desired.The research on the preparation and performances of the porous carbon-based materials has important significance and broad application prospects.In recent years,quinoa,a nutritious and expensive food,has attracted wide attention.When more and more quinoa has been planted,the quinoa straw?QS?become a nonnegligible agricultural waste and available biomass resource.In this work,QS was used as a raw material for preparing the QS-based porous carbon?QSPC?through the method of carbonization and activation.Na OH was selected as the activator because of its lower corrosivity than other activators.Herein,we have devoted our efforts to explore the influence of acitivation conditions on the properties and dye adsorption performances of the products.The produced porous carbon material was used as an adsorbent for removing rhodamine B?Rh B?,a representative dye,from water.The kinetic and thermodynamic properties of the adsorption of the carbon materials toward Rh B were researched.The possible adsorption mechanism was preliminarily discussed.Moreover,through hydrothermal synthesis,Fe₃O₄ magnetic nanoparticles were introduced on the surfaces of the carbon material,and the magnetic composite?Fe₃O₄@QSPC?was prepared.The results are as follows:?1?In the processes of preparing the porous carbon material,the conditions of carbonization and activation,such as reaction time,temperature,and the mass ratio of Na OH to carbon,have a decisive effect on the porosity and dye adsorption performances of the products.It was concluded that the product exhibited the biggest specific surface area(3435.21 m²·g^-1)and the highest dye adsorption capacity(1887 mg·g^-1),when the QS was carbonized at 500 ^oC for 60 mins and then activated at 700 ^oC for 60 mins with the ratio of Na OH to carbon of 4:1.?2?The products were characterized by powder X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FT-IR?,Raman spectroscopy,Zeta potential,N₂ adsorption/desorption experiments,scanning electron microscopy?SEM?,transmission electron microscope?TEM?,and X-ray electron spectroscopy?XPS?.Based on the results,it could be concluded that the porous carbon product was composed of C and O elements.There are a large number of groups containing O and C elements on the surface.The specific surface area of QSPC could reach3435.21 m²·g^-1 The Zeta potential of the product changed when the p H value of the aquesous solution changed.The Zeta potential decreased when the p H value increased.Moreover,Fe₃O₄nanoparticles could be synthesized on the surface of the porous carbon.?3?Rh B was used as a representative dye for evaluating the adsorption performances of the QSPC to dye in water phase.The kinetic studies showed that the pseudo-secondary-order equation could be used to fit the experimental data very well?R²>0.99?.Moreover,the fitting of adsorption data were calculated by the isothermal adsorption model,and the fitting results reveal that Langmuir equation can fit the adsorption isotherm.It indicates that the adsorption of Rh B by QSPC was mainly monomolecular adsorption,and the theoretical maximum adsorption capacity was 1887 mg g^-1 calculated based on the Langmuir equation.The adsorption of QSPC to Rh B could result from the intermolecular interaction,filling of interval space,?-?interaction,hydrogen bond interaction,and electrostatic interaction.?4?The magnetic composite of Fe₃O₄@QSPC can be easily recovered from water utilizing a magnet.In one minute,the recovery rate could reach 90%.When the Fe₃O₄@QSPC was used as the adsorbent to adsorb Rh B from water,it exhibited good reusability.The removal rate of Rh B reached 97%after 5 cyclic adsorption experiments.