Adsorption Of Reactive Brilliant Red Onto Hydrotalcite-like LDHs And Effect Of Lead Ions On The Process

In recent years, clay minerals have gained much attention for its low cost and bio-chemical steability. Layered Double Hydroxide is representative anion layered compounds that can adsorbe anion poluttants.In this study, the research of adsorption activity and mechanism of X-3B onto LDHs are conducted. X-3B is one of the zeo dyes that carry negative charge.Main contents are summarized as follows:(1)Co-precipitation-hydrothermal method was seceted for the synthesis of three kinds of LDHs.The synthesis conditions were optimized by pH, temperature and time. According to the results,pH10.5,180℃and48h was decided as the synthesis conditions.The XRD patterns show that all the synthesized LDHs own good crystality and refularity. The order of specific surface area of the LDHs is Ni/Al-LDH>Mg/Al-LDH>Co/Al-LDH and the pore size is quite the opposite.The zeta potential test illustrate that the pHzpc of LDHs is high and the pHzpc three kinds of LDHs are9.25,9.49, and9.70for Co/Al-LDH, Mg/Al-LDH and Ni/Al-LDH, respectively.(2) LDHs are effective sorbents for X-3B. The Ni/Al-LDH exhibited a higher adsorption capacity, which may result from its larger surface area, broader interlayer space and more active metal (Ni). The kinetic data fit well in the pseudo-second-order kinetic model, while isotherm data were well described by the Langmuir model. The negative value of and indicated spontaneity and showed exothermic nature of X-3B adsorption.Adsorption mechanism was gave us a deeper insight into the adsorption mechanism by proving that hydrogen bonding between the adsorbent and dye molecule played the dominant role in the process and the-SO3was the reaction point.(3) Although Ni/Al-LDH is a kind of anion adsorbent,it can absorbe lead ion as well.This ability comes from the hydroxylated layer structure of LDHs,leading to the surface precipitation of lead ion.the lead ion adsorption is strongly effected by pH.the exsistance of lead ion can promote the adsorption of X-3B by a large margin.the mechanism can be concluded as follows:First,the exsistance of lead ion can elevate the positive charge of LDHs by surface pretipitation.Second,X-3B can replace H2O and form the hydroxylated layer with LDHs.