| Thallium is a highly toxic heavy metal with much greater toxicity than conventional heavy metals such as Hg,Cd and Pb.It has two kinds of valence states in nature:positive one and positive trivalent,the dissolved thallium is mainly in the form of Tl?I?,which is easy to migrate and transform in the environmental medium through water.Tl?I?can enter the organism through drinking water or food chain,and lurk and accumulate in the long-term,and damage the physiological functions and nervous system of the organism.The removal of Tl?I?in water has gradually attracted the attention of researchers.Compared with other methods of removing thallium,adsorption is one of the most promising methods,and the key to adsorption is high-efficiency adsorption.The thallium adsorption materials are mainly based on powdered adsorbents,which makes these adsorbents very limited in practical applications.For this reason,it is quite important to granulate the powdered adsorbent,and it is also one of the current research hotspots.Previous studies have shown that powdered titanium peroxide can efficiently remove Tl?I?from water.As a non-toxic,biodegradable polymer compound,chitosan is also a good binder and skeleton,it can be used to coat the adsorbent material and make beaded granular adsorbent.In this paper,a novel titanium peroxide/chitosan bead adsorbent was prepared by using chitosan as binder,and the prepared adsorbent was characterized systemically and its removal T1?I?performance was systematically explored.Research indicates:?1?The titanium peroxide/chitosan bead particle adsorbent with the diameter of 1.4 to1.8 mm is obtained,and the mechanical strength is high?0.5 to 2 N?,the specific surface area of the granular adsorbent is 3.86m2·g-1,the pore volume is 0.018cm3·g-1.?2?The titanium peroxide/chitosan bead granule adsorbent still maintains the high adsorption capacity of titanium oxide for Tl?I?.When the pH=7.0±0.1,the maximum adsorption capacity for Tl?I?can reach 125.9mg·g-11 and has a higher adsorption rate,the adsorption is chemical adsorption,the appropriate temperature of the adsorption reaction is 25?,which is an exothermic reaction process with an increase in system chaos and spontaneous.The suitable pH range of the adsorbent material is 7.09.0,and the ionic strength has little effect on the adsorption of Tl?I?.The order of the influence of coexisting cations on Tl?I?adsorption is:Cu2+>Ca2+>Mg2+>K+,when the concentration of humic acid is lower than 5mg·L-1,the adsorption of Tl?I?can still be maintained at a high level.?3?The titanium peroxide/chitosan bead adsorbent has certain reproducibility.It can be desorbed-regenerated with nitric acid solution,and the adsorbent material can be reused many times as the removal rate of Tl?I?is kept at 70%,the adsorbent has a good removal effect on thallium in actual water body,and the dosage of the adsorbent is0.1g·L-1,which can reduce the Tl?I?content in the water body below to 2?g·L-11 from2?g·L-1.?4?The Tl?I?removal process is mainly achieved by the exchange reaction of Tl+with the H+ions on the titanium peroxide/chitosan to form an inner sphere complex with-Ti-O-Tl+structure.In summary,the prepared titanium peroxide/chitosan beads have a good mechanical stability,exhibit a good adsorption performance for Tl?I?,and can effectively remove Tl?I?content in actual water bodies as a very promising materials for removing thallium. |
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