Preparation And Dyes Removal Properties Of Multi-forms Layered Double Hydroxides

Wastewater effluents contain synthetic dyes which cause a potential hazard to human beings and to aquatic life.Dye bearing effluents are normally not easily amenable for conventional biological wastewater treatment due to their synthetic origin,and complex aromatic molecular structures which make them difficult to biodegrade.Congo red(CR)and methyl orange(MO)are among the distinctive anionic dyes and extensively use in textile industries,wood pulp,and paper manufacturing.Releasing even a small quantities of these dyes into water can affect the marine life and food chain.Therefore,it is highly desirable to efficiently remove these dyes from water.Adsorption is considered to be a very effective separation technique and it is widely used in wastewater treatment.Among various adsorbents,layered double hydroxides(LDHs)have been attracting considerable attention as environmental friendly materials because of their composition.(1)Nano rod like LDH was synthesized by a simple hydrothermal method.In order to improve the adsorption capacity,LDH was calcined at 500 ~oC.The structure and morphology of the prepared LDH were characterized by XRD,FTIR,SEM,and TEM.The results showed that LDH is in uniform rod like shape with 0.95μm width.The surface area of LDH was 162.5131 m~2/g measured by BET.The removal efficiency of LDH towards the CR was above 96%and the LDH can be regenerate successfully by calcination.Rod like LDH has a cycle ratio of 87%after 6 cycles.(2)In order to investigate the effect of shape on the adsorption capacity,petal like Fe-Mg LDH was fabricated.A well-defined petal like shape was found in SEM and TEM characterization.A comparative adsorption study of CR and MO was carried out.It was found that the fabricated petal like LDH showed great adsorption efficiency towards CR as compare to MO.Equilibrium and kinetic parameters were explored to describe the adsorption process as well as the influence of temperature,p H,and initial concentration on the adsorption capacity were investigated.(3)For the improvement in adsorption capacity,a flower like Ni-Co-LDH was fabricated with large number of pores and its adsorption property to CR was investigated in detail.This LDH featuring a well define flower like shape confirmed by SEM and TEM characterization.The kinetic study revealed that the adsorption process followed the pseudo-second-order kinetic model.The equilibrium data was accurately described by the Langmuir model and the results showed that the adsorption process is chemisorption and endothermic in nature.The maximum adsorption capacity of Ni-Co-LDH calculated from Langmuir model was 1158 mg/g.