Study On Preparation Of Iron-based Nanocomposites And Their Adsorption Behaviors And Mechanism For Arsenic In Water

Arsenic is a metalloid that is widely distributed in the earth's crust.Arsenic and its compounds are a class of carcinogens recognized by the World Health Organization?WHO?and pose a great threat to the health of people around the world.Arsenic pollution in water is a global environmental problem that needs to be solved urgently.It is of great significance to develop a water treatment technology that deeply removes arsenic contamination from water.So far,adsorption technology is still the most feasible and effective arsenic removal technology.Due to its low cost,quick effect and strong applicability,it can be widely used.Adsorption materials are the core of adsorption technology,and the quality of adsorption materials determines the success or failure of adsorption technology.Good adsorbent materials should have the following characteristics:?1?faster adsorption rate;?2?larger adsorption capacity;?3?easy recovery;?4?stable chemical properties,easy recycling and so on.In this paper,two new iron-based adsorbents were prepared and characterized for the removal of inorganic arsenic in water:porous iron oxide/graphene composite?PGA/P-Fe₂O₃?and chitosan-iron oxide/cerium oxide composite material?Fe/Ce-Cs?.And the adsorption performance has been comprehensiv ely studied.The main research contents and results are as follows:?1?The PGA/P-Fe₂O₃ composites were prepared by using Prussian blue as a template to grow in situ on graphene aerogels,and applied to the adsorption of arsenic??,V?.The results show that PGA/P-Fe₂O₃ aerogel has a higher adsorption capacity for arsenic?As???:172.27 mg/?g Fe₂O₃?;As?V?:217.34 mg/?g Fe₂O₃??;It can reach adsorption equilibrium in 30?As????and 5 minutes?As?V??,respectively?m/V=0.5g/L,C₀=5 mg/L?.It is worth noting that high concentrations of As???and As?V?can be reduced to below 10?g/L in 60 and 5 minutes,respectively.This is because the PGA/P-Fe₂O₃ aerogel has a three-dimensional interpenetrating porous structure,which is favorable for the rapid diffusion of arsenic;the porous Fe₂O₃ provides a rich adsorption site for the adsorption of arsenic.In addition,the adsorbent exhibits excellent reusability and is highly resistant to the aquatic environment.The actual realgar tailings wastewater(C₀=3.076 mg L^-1 for As???and 3.225 mg L^-1 for As?V?)can be deep treated(below 10?g L^-1)within 4 h?m/V=0.6 g/L?.The bulk adsorbent of PGA/P-Fe₂O₃ presents a high column treatment capacity of arsenic-containing groundwater?4750 BV for As???,5730 BV for As?V??,producing only 12 BV eluent.This work develops a superior bulk adsorbent for large-scale treatment of arsenic-containing wastewater?Chapter 2?.?2?According to reports in the literature,most of the adsorbent materials have poor affinity for trivalent arsenic,which is not conducive to the removal of arsenic.A common method is to add an oxidizing agent to the arsenic-containing solution to convert As???to As?V?and then treat it.An increase in the operating process leads to an increase in cost,which is obviously not a good method.In this paper,a new Ce/Fe-Cs adsorbent was successfully prepared by simple water bath reflux and alkali droplet ball method.The Ce/Fe-Cs adsorbent has a diameter of 3 mm and is easily separated from the solution after adsorption.It can be seen from the electron micrograph that the Ce/Fe-Cs beads have an interpenetrating network structure,which is beneficial to the diffusion and adsorption of harmful substances.The material was applied to the adsorption of As???and exhibited excellent adsorption properties.The results show that Ce/Fe-Cs has good adsorption performance in a wide pH range?3-9?;the faster adsorption rate can achieve the adsorption equilibrium for 1 mg/L As???within 60 minutes;The higher adsorption amount,for the initial concentration of 60mg/L As???solution,the actual adsorption amount can reach 61.49 mg/g?308 K?;Easy to separate and regenerate,after 5 cycles of experiments,the removal rate of arsenic remains above 95%,showing good chemical stability and reproducibility;In addition,Ce/Fe-Cs exhibits good anti-interference ability to coexisting ions.The change of zero charge point and XPS analysis before and after adsorption showed that the adsorption mechanism of Ce/Fe-Cs on As???was complexation and redox mechanism.These results indicate that Ce/Fe-Cs can be used as a potential and effective renewable adsorbent for the removal of As???from arsenic-containing wastewater?Chapter 3?.