Study On Adsorption Of Heavy Metal In Aqueous Solution With Functional Bentonite

The objective of this work is to remove heavy metal ions from wastewater with new-style functional bentonite adsorption materials. Two different kinds of functional bentonite adsorption materials were synthesized: sodium polyacrylate-bentonite and propyl sulfonic acid-bentonite. The prepared functional bentonite adsorption materials were characterized by FTIR, XRD, Zeta potential measurement, SEM, TG/DTA and N₂ adsorption-desorption isotherm study. Pb²⁺ was used as adsorbate. The influences of various factors?adsorption time, pH, initial concentration? on adsorption capacities were investigated. The adsorption capacities and optimum adsorption conditions were measured. At the same time, adsorption kinetics and adsorption isotherm were studied and reasonable adsorption mechanisms were deduced based on these experimental outcomes. At last, desorption experiments were conducted to evaluate the repeated use. The experimental conclusions provide new approaches and accumulate experience for the appliance of functional bentonite adsorption materials in the remediation of wastewater containing heavy metal ions.The original innovations in this work are as follows:?1? A sodium polyacrylate-bentonite material?PAANa-Bent?, as an adsorbent for heavy metal ions, was synthesized for the first time by in-situ polymerization. A series of analytical methods containing FTIR, zeta potential measurement, SEM, TG/DTA, N₂ adsorption-desorption isotherm study and XRD were used to characterized PAANa-Bent. In addition, to evaluate the adsorption capability of PAANa-Bent, batch experiments were conducted by using Pb²⁺ as an adsorbate. The results demonstrate that PAANa-Bent was prepared successfully and the layered structure of bentonite was protected in polymerization. PAANa-Bent is of more negative surface charges and better dispersity than original bentonite?O-Bent?. The maximum adsorption capacity of PAANa-Bent is 70.41 mg/g at pH = 6, t = 300 min and T = 25 °C, increasing by 113 % compared with O-Bent. Kinetic study shows that the adsorption process of PAANa-Bent obeys pseudo-second-order model and the fittest adsorption isotherm is Freundlich isotherm indicating the heterogeneous nature of PAANa-Bent. Besides, the desorption experiment suggests that the PAANa-Bent can be regenerated easily with 0.1M HCl as stripping agent and the desorption ratio is still more than 91 % after four cycles. Overall, the results indicate that the potential of PAANa-Bent as a low-cost and high efficient adsorbent for Pb²⁺ removal from aqueous solution.?2? The functionalized bentonite?Bent-SO₃H? was prepared by acid activation, anchoring and oxidation of?3-mercaptopropyl? trimethoxysilane. XRD, FTIR and TG/DTA were used to characterize the functionalized bentonite. A series of batch adsorption experiments was performed. The maximum adsorbing capability?54.40 mg/g? increased by 64 % compared with pristine bentonite when pH = 5 and contact time is 180 min. In addition, the equilibrium isotherm data were analyzed using Langmuir and Freundlich isotherm models, while, only the Freundlich model could provide a high correlation. The desorption studies indicated that the functionalized bentonite could be regenerated efficiently with 0.1 M HCl solution. Therefore, the novel functionalized bentonite can be a low-cost and efficient adsorbent for the removal of heavy metal ions from water.?3? On the whole, although the adsorption capacity of PAANa-Bent is higher than Bent-SO₃ H, the synthetic process of Bent-SO₃ H is more simple.