Preparation Of Functionalized Biochars And Their Performance For Adsorption Of Ionic Liquids From Aqueous Solution

The resource utilization of natural biomass has been a research focus.Environmental remediation materials based on agricultural waste can achieve simultaneously good environmental,economic,and social benefits.Biochar is defined as a carbon-rich,porous solid produced by the thermal decomposition of biomass in a reactor with little or no available air and at moderate temperatures.Biochar is defined as a carbon-rich,porous solid produced by the thermal decomposition of biomass in a reactor with little or no available air and at moderate temperatures,which has a large specific surface area,abundant oxygen containing functional groups.To increase binding force between biochar and contaminants,the strategies can be established for tuning the surface functional group,surface polarity and the pore size distribution of the concerned carbon materials by physical and chemical methods.Ionic liquids?ILs?,known as“green solvents”,which exhibit toxicity to organisms.The releasing of ILs into the water systems,and have become a new type of low concentration pollutants.How to efficiently remove these ILs from water will be an important issue to be tackled soon.In this work,we prepared a series of biochar-based adsorbents with different agricultural wastes?bamboo,peanut shell,corn stalk and wheat straw?,which exhibited superior removal capacity for ILs from aqueous solution.And adsorbents greatly reduced biological toxicity of ILs towards seedlings growth in wheat seeds germination.The as-prepared adsorbents thus could be used for remediation of contaminated water and soil.The details are as follows:?1?Bamboo was used as feedstock to prepare low-cost and effective biosorbents to remove a hydrophilic ionic liquid,1-butyl-3-methyl-imidazolium chloride?[BMIM]Cl?,from aqueous solutions.Modified biochars produced from bamboon through carbonization and KOH/?NH₄?₂S₂O₈ modification to be used as low-cost adsorbents.Characterization of the biosorbents showed that BB-K-N had high surface areas,large pore volume,large micropore volume,and abundant oxygen-containing functional groups.The results showed that modified biochar?BB-K-N?had better adsorption performance than both pristine biochar?BB?and intermediate biochar?BB-K?toward[BMIM]Cl,which led to superior adsorption capacity of 0.625 mmol/g for[BMIM]Cl.[BMIM]Cl adsorption on BB-K-N fitted well with the pseudo-second-order model and Freundlich isotherm.The exhausted adsorbents were regenerated effectively by 0.1 mol/L HCl.Furthermore,the wheat seedlings growth of[BMIM]Cl-laden BB-K-N group were similar to that of control groups.The adsorption of[BMIM]Cl on the modified biochar greatly reduced its biological toxicity towards seedlings growth.?2?Biosorbents based on agricultural wastes for ionic liquid removal:An approach to agricultural wastes management.Modified biochars produced from different agricultural solid waste?peanut shell,corn stalk and wheat straw?via carbonization and KOH/?NH₄?₂S₂O₈ to be used as low-cost adsorbents?denoted as PB-K-N,CB-K-N and WB-K-N?removal of ionic liquid?[BMIM]Cl?.Herein,the biosorbents based on peanut shell,corn stalk and wheat straw all exhibited higher[BMIM]Cl removal than many other carbonaceous adsorbents and the adsorption capacities were as the following:PB-K-N>CB-K-N>WB-K-N.The characterizations of biosorbents indicated that they had great deal of similarity in morphological,textural,surface chemical properties and adsorption mechanism such as possessing simultaneously accessible microporous structure and abundant oxygen containing functional groups.Additionally,adsorption of[BMIM]Cl onto PB-K-N,CB-K-N and WB-K-N prepared from the modified process,which were all better described by pseudo-second order kinetic and Freundlich isotherm models.The adsorption capacity is mainly associated with the micropore structure and oxygen containing functional groups of biosorbents.The viable approach could also be applied in other biomass materials treatment for recycling agricultural wastes to ease their disposal pressure.?3?The toxic effects of ILs on wheat seedlings and PB-K-N biochar inhibited their phytotoxicity.In order to explore the toxic effects of ILs on plants,we selected eight ILs with the different cations?[BMIM]⁺,[Emim]⁺,[OMIM]⁺,[Domim]⁺,[Bpy]⁺?and anions?Br^-,BF₄^-,CH₃COO^-,C₇H₅OO^-?to study their toxic effect toward wheat.The ILs with the same anion but different carbon chain lengths had increasing toxic effects on the wheat seedlings with increasing the carbon chain lengths,which means the carbon chain lengths have a great influence on the toxicity of ILs.The initial concentration of different ILs adsorption on PB-K-N was investigation,which determined maximum adsorption capacities.Herein,PB-K-N based on peanut shell exhibited higher ILs removal.Furthermore,adsorption of ILs on the PB-K-N greatly reduced and removed their biological toxicity towards seedlings growth in wheat seeds germination.Synthesizing above all outcomes,the subject prepared biosorbents derived from three agricultural wastes by carbonization and modification using KOH/?NH₄?₂S₂O₈,the viable modification method could also be applied in other biomass waste feedstocks treatment;The as-prepared adsorbents efficiently ILs removal and greatly inhibited biological toxicity of ILs towards wheat seeds germination.