Biochar belongs to the category of low-cost, stable, and environmentally benign carbon-based materials. In this article, the reasons that highlight the advantages of biochar materials to be used in carbon dioxide (CO_(2)) adsorption are briefly viewed with recent examples. Also, the issues to be solved for recommending biochar materials in the practical applications are listed.
Antony RajendranArumugam SakthivelZhiwei DongWenying Li
Naphthenic acids,NAs,are a major contaminant of concern and a focus of much research around remediation of oil sand process affected waters,OSPW.Using activated carbon adsorbents are an attractive option given their low cost of fabrication and implementation.A deeper evaluation of the effect NA structural differences have on uptake affinity is warranted.Here we provide an in-depth exploration of NA adsorption including many more model NA species than have been assessed previously with evaluation of adsorption kinetics and isotherms at the relevant alkaline pH of OSPW using several different carbon adsorbents with pH buffering to simulate the behaviour of real OSPW.Uptake for the NA varied considerably regardless of the activated carbon used,ranging from 350 mg/g to near zero highlighting recalcitrant NAs.The equilibrium data was explored to identify structural features of these species and key physiochemical properties that influence adsorption.We found that certainNAwill be resistant to adsorptionwhen hydrophobic adsorbents are used.Adsorption isotherm modelling helped explore interactions occurring at the interface between NA and adsorbent surfaces.We identified the importance of NA hydrophobicity for activated carbon uptake.Evidence is also presented that indicates favorable hydrogen bonding between certain NA and surface site hydroxyl groups,demonstrating the importance of adsorbent surface functionality for NA uptake.This research highlights the challenges associated with removing NAs from OSPW through adsorption and also identifies howadsorbent surface chemistry modification can be used to increase the removal efficiency of recalcitrant NA species.
Metal-Organic Framework(MOF)have gained widespread attention as potential adsorbents for the removal of perfluorooctanoic acid(PFOA).However,single-component MOF often exhibit limitations in adsorption capacity,functionality,and pore structure.Hereby,we innovatively designed and synthesized a dual-metal core-shell MOF composite adsorbent,MIL-101(Cr)@ZIF-8(a chromium-zinc bimetallic MOF,CZDM),which exhibits an excellent adsorption removal performance of PFOA from aqueous solutions.The results showed that the CZDM composite material has a high specific surface area(2091 m^(2)/g),with pore structures exhibiting typical micropores(∼1.16 nm)and mesopores(∼3.4 nm),which are crucial for the efficient adsorption of PFOA.SEM and TEM images revealed that CZDM has a uniform core-shell morphology,with MIL-101(Cr)as the core and ZIF-8 as the shell,maintaining a stable and intact structure.EDX analysis further confirmed the successful incorporation of Cr and Zn elements.Batch experiments evaluated the effects of temperature,solution pH,and PFOA concentration on adsorption efficiency.The results demonstrated that the CZDM-3 adsorbent exhibited rapid adsorption kinetics and good PFOA removal efficiency across a wide pH range.The superior adsorption performance of CZDM is attributed to the synergistic effect of the dual-metal active sites,optimized pore structure,electrostatic interactions,and coordination bonds.The maximum adsorption capacity for PFOA reached 625.5 mg/g,with equilibrium achieved within 60 min,outperforming some related reported adsorbents.The experimental data of the adsorption process fit well with both Langmuir adsorption isotherms and pseudo-second-order kinetics models,indicating that the adsorption process is spontaneous,endothermic,and accompanied by an increase in entropy.Notably,even after five cycles,the CZDM material maintained high removal efficiency toward PFOA.This study advances a new synthesizing strategy of the MOF@MOF,and the CZDM exhibits a potential application in PFOA elimination from wat
Heng LinZhouheng XiaKunpeng XueXiaojing ZhouYifan YaoNa MaWei Dai
