| With the continuous development of industry and the acceleration of urbanization,the problem of water pollution is becoming more and more serious.A variety of treatment methods have been developed to effectively solve the problem of water pollution.Among them,adsorption is widely used due to its low cost,high efficiency,ease of operation and other advantages.So far,adsorbents from various biomass after different element doping or modification are used for pollutants adsorption,which has become a research hotspot.However,the reported biomass directly as an adsorbent has a low adsorption capacity and poor reuse performance,the pore size of the prepared porous biochar and bulk antibiotic molecule is not match very well although biochar has certain adsorption performance,there are only a small amount of oxygen-containing groups on the surface of biochar,all the above shortcoming restrict their practical application.In addition,photocatalytic degradation of organic pollutants in water is also one of the great concerns.Graphite carbon nitride(g-C3N4)is a common visible light catalyst,which has the advantages of wide absorption spectrum and low cost,etc.However,there are some disadvantages in the application of g-C3N4 like limited specific surface area,fast recombination of photogenerated electrons and holes,and low quantum efficiency,and others.How to adjust the band structure and enhance the absorption of visible light of g-C3N4 is an urgent problem.Therefore,in this paper,a series of biochar based adsorbents with different characteristics are designed to control the pore structure,specific surface area and surface adsorption sites of biochar,to enhance the adsorption performance of specific organic pollutants,and the adsorption mechanisms were studied.Moreover,the visible light catalyst g-C3N4 was doped by FR as a carbon source being its high carbon content,and improves the photodegradation performance of dyes and antibiotics.Meanwhile,considering active hydrophobic small molecules of FR liquefaction,it can be designed to coal water slurry additive suitable for low rank coal,and the interaction mechanism between the additive and coal particles was studied.The main results contents are as follows:(1)The removal of methyl orange(MO)and Rhodamine B(RhB)from water by FR was studied.The morphology and structure of FR before and after dye adsorption were analyzed by various characterization methods.It was found that FR exhibited a mesoporous-dominated hierarchical pore structure and had abundant oxygen-containing functional groups on its surface,Adsorption mechanism of both dyes might be involved with electrostatic interaction,mesoporous filling,hydrogen bond and ?-? interaction.The maximum adsorption capacity of FR for MO and RhB was 54.95 mg/g and 37.93 mg/g respectively,which was 43.7%and 39.5%higher than that of other bio-sorbents.FR could be reused for more than five times,and showed a unique potential for the removal of different types of dyes from water.(2)A novel N-doped biochar(NBC)was prepared by one-step low-temperature pyrolysis of furfural residue and urea for adsorption and hydrothermal catalytic degradation of chlortetracycline(CTC).NBC presented a graphite-like structure with nitrogen-containing functional groups and larger mesopore structure by characterization.The adsorption studies showed that NBC could reach adsorption equilibrium faster than other biochar adsorbents.The maximum adsorption capacity of NBC for CTC was 44.3 mg/g,which can be reused.The adsorption was fitted well with the Freundlich isotherm model and the pseudo-second-order kinetic model.The adsorption mechanism could be ascribed to the synergistic effects of pore-filling interaction,?-? interaction,electrostatic interaction,and hydrogen bonding.Furthermore,the nitrogen-containing groups in NBC could catalyze the degradation of CTC under hydrothermal condition,and the degradation pathway of CTC was analyzed.Hence NBC is a promising biochar material for CTC antibiotics adsorption in water.(3)Magnetic biochar(MBC)was prepared from FR by carbonization and chemical precipitation,and was used to remove tetracycline(TC)in water.The adsorption rate of TC by MBC was the highest when the ratio of iron to biochar was 2:1.The characterization including SEM,XRD,VSM and Zeta showed that MBC had a larger mesopore structure and its saturation magnetization was 5.38 emu/g and the Zeta potential was-21.14 mV.MBC easily dispersed in water compared with biochar.The adsorption of TC by MBC was affected by the initial TC concentration,contact time,adsorbent dosage and the pH value of the solution.When the pH value was 6.0,the adsorption capacity of TC was the largest(40.2 mg/g).In addition,the adsorption was fitted well with the Langmuir isotherm model and the pseudo-second-order kinetic model,the maximum adsorption capacity of MBC for TC was 43.5 mg/g,and adsorption mechanism was analyzed.MBC can be recycling by magnetic separation,which showed a potential application in adsorbing antibiotics from aqueous solution.(4)A series of graphite carbon nitride(g-C3N4)with different amount of carbon doping(3%-15%)were successfully synthesized by using FR liquefaction as carbon source.Results show that C-doping can regulate the aggregation of g-C3N4,but the crystal structure of g-C3N4 does not change.The photocatalytic performance of C-doped g-C3N4 was evaluated by the photocatalytic degradation of rhodamine B(RhB)and tetracycline(TC)under visible light irradiation.Compared to pure g-C3N4,5%C-doped g-C3N4(5%CCN)exhibited optimum photocatalytic efficiency for the two organic pollutants.In addition,5%CCN showed an excellent stability in the catalytic degradation of RhB and TC.Moreover,the catalyst can also degrade other dyes,such as methyl orange,fuchsin basic and methylene blue.By further experimental study,the catalyst can also degrade other dyes,such as methyl orange,fuchsin basic and methylene blue.And the superoxide radical(·O2-)was proven to be the main active species during the degradation of TC.Therefore,this study provides a new strategy for improving the photocatalytic performance of g-C3N4.(5)Furfural residue liquefaction was sulfonated by sulfuric acid and neutralized by alkali,which was used as the additive for coal water slurry(CWS)from low rank coal.The sulfonation process of FRS was optimized with the slurry performance of low rank coal as the evaluation index.In addition,the structure characteristics of FRS and three kinds of commercial CWS additives were compared and analyzed.The results showed that all four additives contained hydrophilic sulfonic group and hydrophobic aromatic rings.The order of Zeta potential of low rank coal was consistent with the change of sulfonation degree of additives,and the wettability of FRS to coal surface was the best.Under the same pulping conditions,FRS had the best stability for the hard to pulp coal than other three additives.The interaction mechanism of FRS and coal particle surface was also proposed.Taken together,in this paper,a series of different adsorbents,photocatalyst and coal water slurry additive are designed by using the low-cost furfural residue as the main material,which provides a new application prospect for the resource utilization of abundant furfural residue. |
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