Pyrolysis Of Heavy-Metal-Contaminated Biomass To Synthesize Nano-Metal Modified Biochar

Heavy metal contaminated biomass(MB)is widely derived from biomass-based environmental remediation or industrial processes such as:phytoremediation,biorefinery,biosorption,or natural plants growth in contaminated soil.This kind of waste can easily cause secondary pollution and has been increasing every year.Meanwhile,the heavy metal minerals and biomass components are important resources,which can be used to prepare metal nanoparticles modified carbon materials.Based on previous literature,the preparation of metal nanoparticles modified biochar from MB is highly acknowledged,because it could achieve the purpose of simultaneous reuse of metal and biomass.By co-producing bio-oil and fuel gas,the pyrolysis of MB for the biochar production process is considered an economically attractive option.However,in the pyrolysis process of MB for nano metal modified biochar synthesis,the effects of heavy metal on the thermal degradation mechanism of biomass,physicochemical properties,adsorption,and electrochemical application performance of biochar materials are still unclear.Meanwhile,the studies on the pore diameter regulation strategy of nano metal modified biochar material are still insufficient.Therefore,in this study,the thermal degradation mechanism of MB was studied.Nano ZnO/ZnS modified biochar,Fe₃O₄ magnetic biochar,and PbO/ZnO modified hierarchical porous carbon were prepared using MB from different sources.In addition,the adsorption and electrochemical properties of modified carbon materials were also studied.This study aims to provide a basis for promoting the recycling of MB,and the preparation of nano metal modified carbon materials.The influences of zinc mineral on pyrolysis characteristics,activation energy and thermal decomposition kinetics of three major biomass components(i.e.,hemicellulose,cellulose,lignin)were investigated using TGA/DTG combined with iso-conversional method and integral master-plots method.TGA results showed that the degradation of hemicellulose was inhibited,while the presence of heavy metals promoted cellulose degradation.At 5 K min^-1 heating rate,to 900K final temperature,the weight loss rate of hemicellulose decreased from 63.6wt.%to 41.5wt.%,while cellulose increased from 20.5wt.%to 39.8wt.%.In the presence of zinc mineral,the activation energy of three pseudo-components increased,which ultimately indicated that the thermal decomposition pathway changed to the cyclization to form C4-C5 products.The kinetic models of the three components were fitted with F2.0(elementary reaction),A1.8(nuclear growth)and F2.3(elementary reaction).Meanwhile,the kinetic models of the three components of MB were fitted with F2.8,F3.0,and F3.2,respectively,indicated that the zinc minerals were beneficial to the occurrence of multimolecular repolymerization of the C4-C5 products.The zinc minerals accelerated the collisions between molecules or free radicals of C4-C5 to form biochar network.These conclusions provide a theoretical basis for the preparation of biochar from MB.A novel nano ZnO/ZnS modified biochar was synthesized from the slow pyrolysis of zinc contaminated corn stover obtained from the biosorption process.The characterization results indicated that the zinc mineral modified biochar had a better porous structure(S1=397.45m²g^-1 and Vt=0.430cm³g^-1)than the common biochar(St=102.96m²g^-1 and Vt=0.195cm³ g^-1).and zinc minerals were evenly anchored on the biochar surface as nano ZnO/ZnS.Batch sorption experiments showed that the nano ZnO/ZnS modified biochar showed strong sorption ability to Pb(?),Cu(?)and Cr(?)with maximum sorption capacities of 135.75mgg^-1.91.20mg g^-1 and 24.51mgg^-1,respectively,which were significantly higher than the common biochar(63.29mg g^-1,27.05mg g^-1 and 15.23mg g^-1.respectively).In the adsorption process,nano ZnO/ZnS accounted for 35.1%,39.0%and 21.3%of the adsorption.Based on the comprehensive characterizations and adsorption performance,the enhancement of the metal removal by the nano ZnO/ZnS modified biochar was mainly attributed to the hydroxyl groups on the surface of nano ZnO/ZnS particles and well-developed porous structure which was catalyzed by zinc salt during the pyrolysis process.These findings suggested that the utilization of MB to develop nano mineral based modified biochar could be an attractive and economically feasible approach.Magnetic mesoporous biochar was prepared from iron-containing furfural residue(FRMB).And adsorption of ionizable aromatic pollutant(norfloxacin(NOR))on FRMB in the presence of interference factors was investigated.The characterization results showed that the biochar prepared from furfural residue had a good specific surface area(463.00 m2g^-1)and total pore volume(0.524cm³ g^-1),which were higher than the biochar prepared by the impregnation method(77.86m²g^-1 and 0.136cm³ g^-1).The mesoporous structure(4.53 nm)of FRMB was favorable for the adsorption of pollutants with larger molecular diameter,and the maximum adsorption capacity of NOR was 299.57mg g^-1.The adsorption experiment results show ed that the adsorption binding force between the mesoporous biochar and NOR was ascribed to ?-?bond and electrostatic effect.Therefore,its strong adsorption binding force enabled it to avoid the interference of other ions in wastewater.Adsorption results showed that the anionic surfactants-sodium dodecyl sulfate(SDS)and sodium dodecyl benzene sulfonate(SDBS)had a synergistic effect on the adsorption of NOR.In the presence of SDS and SDBS,the maximum sorption capacities of NOR reached up to 698.59mg g^-1 and 589.94mg g^-1,respectively.This work highlights the excellent adsorption capacity and anti-interference performance of magnetic mesoporous biochar derived from furfural residue.PbO/ZnO modified hierarchical porous carbon was synthesized from Sedum plumbizincicola contaminated with various heavy metals harvested from phytoremediation process.The characterization results showed that the specific surface area(1727.41m²g^-1)and total pore volume(0.304g^-1cm³)of ZnO/PbO modified porous carbon were much higher than that of the common porous carbon(249.61m²g^-1 and 0.044cm³ g^-1)prepared under the same conditions(1073 K temperature,40 mL min-1 CO2 flow rate,and 40 min residence time).Both micropores and mesopores were present in samples to form a hierarchical structure of micromesoporous.The capacitance of ZnO/PbO modified biochar was 145.3 F g^-1(1 A g^-1),which was 2.81 times higher than the ordinary biochar of 51.7 F g^-1(l A g^-1).The ZnO/PbO modified biochar had a power density of 878.4 W kg^-1 and an energy density of 67.9 Wh kg^-1.It is found that the ZnO/PbO modified biochar prepared by pyrolysis of Sedum plumbizincicola with heavy metals could be used in high-performance energy storage equipment such as electrode materials for supercapacitors.In summary,metal nanoparticles modified biochar materials derived from MB has good physicochemical properties,adsorption performance and could be applied in the field of electrochemistry through pore size regulation.