The Study On Adsorption Performance Of Immobilized Marine Diatom Bio-adsorbents For The Removal Of Lead Ions From Aqueous Solution

Heavy metal pollution is becoming a serious environmental problem in nowadays society.The development of adsorbents with high adsorption capacity of heavy metal ions is one of the hotspots in the field of heavy metal wastewater treatment.Sodium alginate was used to immobilize marine diatom powder in this study.Through single factor and orthogonal experiments,the effects of preparation conditions on adsorption of lead ions by immobilized beads were studied.Effects of various factors on adsorption properties by immobilized beads which were prepared by the method of optimization were studied.The experimental results showed that the suitable embedding conditions of immobilized marine diatom adsorbents were as follows:diatom power dosage of 5.0 g/100 ml SA,sodium alginate concentration of 2%,calcium chloride concentration of 2%,cross-linking time of 1 h,and bead diameter of 3.5 mm.The favorable pH value of the adsorption on immobilized beads is 4?5.The removal rate of Pb²⁺in the solution increased with the solid-liquid ratio,and the adsorption capacity increased first and then decreased.The adsorption equilibrium could be reached in 24 h.The removal rate of Pb²⁺in the solution decreased and the adsorption capacity increased with Pb²⁺initial concentration in solution.NaCl had acceleration to the adsorption properties on immobilized beads,Ca?NO₃?₂ and Mg?NO₃?₂ had inhibition effects.Through kinetic and isothermal adsorption studies,the kinetic and isothermal adsorption properties of the adsorption process were determined.The physical structure and surface chemical properties of immobilized beads were characterized by scanning electron microscopy,energy dispersive spectroscopy and infrared spectroscopy.The removal mechanism of Pb²⁺by adsorbent was discussed.The isothermal adsorption properties of Pb²⁺adsorption on immobilized beads could be best described by the Langmuir isothermal adsorption model,with a theoretical maximum adsorption capacity of 909.09 mg·g^-1.The kinetic process of Pb²⁺adsorption on immobilized beads was well fitted by the pseudo-second-order model.Immobilized marine diatom bio-adsorbents is a porous material that allows Pb²⁺to adsorb as a large number of crystals in the form of Pb-containing complexes on its surface and interior.After adsorption of Pb²⁺,the structure and main groups of the adsorbent did not change.