Preparation And Application Of Modified Barium Phosphate Micro-nano Materials For The Purification Of Methyl Blue Dye From Water

At present,many environmental problems caused by dye-wastewater need to be solved.The purification of methyl blue wastewater has received increasing attentions.Phosphate materials show good potential in dye purification for they are environmentally friendly and easily prepared.In this paper,we prepared four barium phosphate mrcro-nano materials by changing the reactants and surfactants.They are barium phosphate（BP）,barium hydrogen phosphate（BHP）,barium hydroxyl phosphate（BPO）,and sodium barium phosphate（NBP）materials,respectively.The performance and mechanism of these materials for the purification of MB from wastewater were systematically studied and the research contents are as follows:1.Four new phosphate materials,BP,BPO,BHP,and NBP were prepared by the hydrothermal method and characterized in detail.As shown in the SEM and EDS results,the BP nanosheets possessed a length of 3μm and a thickness of 30 nm.BHP micron columns showed a size of about 4μm.BPO was composed of nanoparticles and nanorods with a diameter of about 100 nm.NBP were particles with an average size of 4μm.TEM and XRD results show that these materials are single crystal with good crystallinity and purity.The BET results showed that the specific surface areas of BP,BPO,BHP,and NBP were 9.47,14.69,14.37,and 13.80 m²/g,respectively.The particle size distribution results showed that the average particle size of BP,BPO,BHP,and NBP was 484,2488,1307,and 685 nm,respectively.FT-IR results indicated that PO₄^3-groups were the main groups in these materials.Zeta potential results showed that the surface charges of BP,BPO,BHP,and NBP were-17.70,-8.83,-12.80 and-11.00 m V,respectively.TGA results showed that the mass loss rate of the four phosphate materials was all less than 4.2%in the temperature range of 30-1000°C,indicating good thermal stability.In the leaching experiments in the range of 5<pH<10,all the materials showed a mass loss of less than 10%,implying their good chemical stability.The anionic surfactant sodium dodecyl benzene sulfonate（SDBS）and cationic surfactant cetyltrimethyl ammonium bromide（CTAB）had no significant effect on the morphology and composition of the materials.2.The effects of reaction temperature and material dosage on the performance of MB purification by four materials were studied.The results showed that the optimal reaction conditions for BP,BPO,BHP,and NBP were 15°C and 1.0 g/L.The effect of solution pH on the purification performance of MB by four materials was studied.At the range of 5<pH<10,the purification performance of BPO increased with the increasing solution pH,while the purification performance of BP,BHP,and NBP showed no obvious change.The kinetic results showed that the MB purification process by all these materials fitted well to the pseudo-ssecond-order kinetic model.Thermodynamic results showed that the MB purification processe by NBP and BPO agreed well with the Langmuir model and their adsorption capacities were 400.10 mg/g and 232.55 mg/g,respectively.The MB purification process by BP and BHP fitted to the Freundlich model.The adhered cationic surfactant（CTAB）to the surface of these materials was helpful for purifying anionic MB ions,and their purification capacities followed an order of NBP（236.80 mg/g）>BP（218.63 mg/g）>BPO（186.51 mg/g）>BHP（79.12 mg/g）.The purification performance of BP,BPO,BHP,and NBP prepared with anionic surfactant SDBS decreased slightly,which may be due to the electrostatic repulsion.3.The pH change of aqueous solution due to the addition of the materials at the initial stage of purification process was detailly studied.The results showed that the pH of deionized water increased from 6.3 to 8.1,8.7,6.5,and 12.3after adding BP,BPO,BHP,and NBP in the deionized water,respectively.In the mean time,the UV absorbance of MB solutions decreased from 0.78 to 0.76,0.75,0.72 and 0.69,respectively,indicating that the increase of MB solution pH due to the addition of materials can be helpful for the decolorization of MB solution.4.The MB purification mechanisms of BP and NBP with better performance were further studied.The FT-IR results showed that the characteristic peaks of MB were existent in the reclaimed materials,indicating the extence of MB molecules on used BP and NBP.On basis of the FT-IR results and the XPS results,the purification mechanism by BP and NBP may be the hydrogen bonding between the oxygen atoms in the PO₄^3-groups and the hydrogen atoms of the N–H groups in MB.In addition,the ionic bonding between the cations in the material and the–SO₃^-in MB contributed a lot to the purification mechanism.Especially,Ba²⁺in NBP was partially replaced by Na⁺,which resulted in more crystal defects and higher surface activity of NBP.Furthermore,Na⁺in NBP may enhance the Lewis acid-base interaction between cations in NBP and–SO₃^-in MB.In conclusion,the NBP composite material in this paper is cheap and easy to obtain,and its adsorption capacity is better than other reports.In conclusion,the NBP composite in this paper is cheap and easy to obtain,and its adsorption capacity is better than many reports.It is a new composite material with good application potential for purifying MB solution.