Study On Preparation And Modification Of Black Phosphorus And The Adsorption Performance For Dyes In Water

In recent years,with the rise development of the printing and dyeing industry,dye pollution in the water environment has become increasingly serious.Water dye pollution is usually accompanied by the characteristics of high chroma,high organic content,high toxicity and refractory degradation,which can easily lead to the deterioration of water quality and may cause a series of risks to the ecosystem and human health.Therefore,the global water environment dye pollution problem has received more and more attention,further research and development of dye pollution and waste water treatment technology has also become a research hotspot in the field of water environmental protection.So far,dye pollution and waste water treatment technologies mainly include physics,chemistry,biology and the coupling of multiple treatment methods.Some pollution and waste water containing dyes is refractory organic wastewater and is not suitable for biological treatment.Some chemical methods（such as chemical oxidation method,electrochemical method,etc.）can generate some highly toxic intermediate products during the treatment process,which will cause more serious harm to human health and the ecological environment.There is a problem of high cost when large-scale operating.The adsorption method mainly uses the porous structure and active sites of the adsorbent to remove pollutants.It has many advantages such as low price,simple process,convenient operation,easy management,and is suitable for process improvement of the original treatment factory.It can be regarded as an effective way to treat dye pollution and waste water.Although there have been activated carbon（AC）,graphene（GP）,zeolite,etc.However,the research and development of new adsorbents,the clarification of their adsorption mechanism and influencing factors on dyes,and the exploration of their modification methods are still the focus of current research in this field,which have important scientific significance.Black phosphorus（BP）is a conductive crystal with metallic luster,composed of phosphorus atoms.BP also has a layered structure similar to GP and transition metal sulfide（TMS）,which is connected by strong intra-layer P-P bonds and weak inter-layer van der Waals forces.As the rising star of two-dimensional（2D）nanomaterials,BP and black phosphorene（BPR）have received widespread attention.Although there have been many research reports about BP in the optoelectronics field,there are few researches on BP and BPR adsorbing dyes,and fewer researches on BPR modification.Inspired by the high drug loading of BPR,in this paper,BP,BPR and sulfonated black phosphorene（BPRS）were prepared by vapor deposition,liquid phase exfoliation and sulfonation modification method,respectively.They were used as adsorbents to remove cationic dye methylene blue（MB）,anionic dye congo red（CR）and non-ionic dye disperse yellow E-3G（DY）from water.Through the study of adsorption kinetics,adsorption isotherms,adsorption thermodynamics,desorption and influencing factors（temperature and pH）,the adsorption capacities have been compared with other materials.The adsorption mechanisms of BP,BPR and BPRS on MB,CR and DY have been revealed.The influencing factors have been clarified,which can provide scientific basis and basic data for the application of BP and BP-based materials in the environmental field.The main research results of this paper are listed as follows:（1）Red phosphorus（RP）was used as raw material,BP was prepared by vapor deposition,BPR was prepared by liquid phase exfoliation,and BPRS was prepared by sulfonation modification successfully.The analysis results of scanning electron microscope（SEM）and X-ray energy spectrum（EDS）showed that compared with BP,BPR and BPRS are peeled off by ultrasound,the structure was broken and became smaller.BPR was successfully sulfonated to prepare BPRS.The analysis results of X-ray diffraction（XRD）and Raman spectroscopy showed that both BPR and BPRS were BP-based materials.The analysis results of atomic force microscope（AFM）showed that the number of BP layers was 31-47,the number of BPR layers was 3-5,and the number of BPRS layers was 5-6,the thickness of BPR and BPRS was thinner than that of BP.The analysis results of Brunauer-Emmett-Teller（BET）showed that the specific surface area（SSA）of BP,BPR and BPRS were 6.78,6.96,and 7.72m²·g^-1,respectively,and the average pore diameter were 13.99,12.75,and 12.81 nm,respectively,which were all mesoporous adsorbents.The analysis results of fourier transform infrared（FTIR）spectrometer showed that the main functional group involved in the adsorption reaction was P-P,BPR introduced sulfonic acid functional group（-SO₃H）,and was modified to generate BPRS successfully.（2）The optimal pH for BP and BPR to adsorb 10 mL MB(20 mg·L^-1)was 2.70,the optimal pH for BPRS to adsorb MB was 8.85,and the optimal adsorbent dosage was 2 mg.Both the quasi-first-order kinetic model and the Langmuir model were suitable to describe the adsorption processes of MB by BP,BPR and BPRS,the q_mwere 84.03,91.74,and 140.85 mg·g^-1,respectively.The thermodynamic parameters indicated that the adsorption processes were all spontaneous,entropy increased,and endothermic reaction.During the desorption processes,the q_e,desorption of MB on BP,BPR and BPRS were 6.15,7.63,and 8.23 mg·g^-1,respectively,and their desorption efficiencies were 9.18,8.84,and 8.24%,respectively.（3）The optimal pH for BP,BPR and BPRS to adsorb 10 mL CR(1000 mg·L^-1)was 3.70,and the optimal adsorbent dosage was 5 mg.Both the quasi-second-order kinetic model and the Freundlich model were suitable to describe the adsorption processes of CR by BP,BPR,and BPRS,the q_m were 1416.36,1672.41,and 1741.73mg·g^-1,respectively.The thermodynamic parameters showed that the adsorption processes were all spontaneous,entropy increased,and endothermic reaction.During the desorption processes,the q_e,desorption of CR on BP,BPR and BPRS were 152.02,161.32,and 166.83 mg·g^-1,respectively,and the desorption efficiencies were 11.31,9.97,and 9.63%,respectively.（4）The optimal pH for BP,BPR and BPRS to adsorb 10 mL DY(100 mg·L^-1)was 7.50,and the optimal adsorbent dosage was 4 mg.Both the quasi-second-order kinetic model and Freundlich model were suitable to describe the adsorption processes of DY by BP,BPR and BPRS,the q_m were 182.19,243.25,and 269.47mg·g^-1,respectively.The thermodynamic parameters indicate that the adsorption processes were all spontaneous and exothermic reaction.The entropy increased during the adsorption processes of DY by BP and BPR,and the entropy decreased during the adsorption process of DY by BPRS.During the desorption processes,the q_e,desorption of DY on BP,BPR and BPRS were 15.39,17.11,and 19.38 mg·g^-1,respectively,and the desorption efficiencies were 8.70,8.17,and 8.78%,respectively.In this work,the prepared BP and BP-based materials have ideal adsorption effects for MB,CR and DY,and have good application prospects in dye pollution and waste water treatment field.The adsorption mechanisms mainly include hydrophobic interaction,hydrogen bonding interaction,functional group and wrinkle-induced adsorption,the effect of electrostatic interaction is relatively small.