Study On Treatment Of Anionic Wastewater Via Forming Process Of Layered Double Hydroxide By One-Pot Method

With the development of economy and industry,kinds of anionic wastewater grow quickly in China,giving a lot of pressure to environment and human beings.LDHs exhibit several excellent properties such as ion-exchange ability,large specific surface area,easy accessibility and good environmental compatibility,therefore,often employed in environmental field.In this study,Zn(NO3)2 and Al(NO3)3 solution was added dropwise to wastewater,using alkali and anionic contaminants to directly synthesize ZnAl-LDH in wastewater and at the same time incorporating contaminants from wastewater into the interlayers,using this one-pot method instead of traditionalmethod.XRD and SEM were employed to analyze the samples’ structure and morphology.The software of molecular simulation was employed to calculate the molecular arrangement in the interlayer and the bonding energy between the sheet of LDHs and the anion.One-pot method was used to treat alkaline arsenic-containing wastewater(As(V)=200 mg/L,pH=12)(anionic inorganic wastewater).The result showed the removal efficiency of As(V)was almost 100% and the pH of the treated alkaline wastewater decreased from 12 to 7.47.The incorporated As(V)from 100 mL wasterwater can be released 96.2 % into 10 m L Na2CO3 solution for disposal or recovery.The LDHs was then dissolved in HNO3 and the solution can be used to treat wastewater to reform Zn-Al-LDH for further removal of arsenate.After four times recycles,Al/Zn below 1/5 made removal and release ability disappear,but the process can be repeated by replenishing the solution with Al3+.For methyl orange(MO)wastewater(anionic organic wastewater),one-pot method had good removal efficiency(almost 100%)and large removal capacity(1.273g/g),which was corresponding to the added aluminum and the removal process fitted to Langmuir model.In addition,methylene blue(MB)was also removed effectively while maintaining the high removal efficiency of MO.MB entered and trapped into the interlayer by hydrophobic interaction and the removal process fitted to Freundlich model.Wastewater containing sodium chromate(Cr)and MO was also treated by one-pot method.Both of the contaminants could be totally removed.In the removal process of this mixed wastewater,MO was removed first,Cr followed by totally removal of MO.By this method,the two mixed contaminants can be separated.Zinc hydroxide as the precursorput into Al(NO3)3 solution can transform to LDHs phase.In the transformation process,aluminum enter into zinc hydroxide and replace zinc quickly to transform it into LDHs by creating positive charges and incorporating anions.The results confirmed the process of the one-pot method and mechanism of contaminant removal.