Study On The Adsorption Properties Of Thermally Modified Environmentally Friendly Materials For Antimony And Lead

With the development of industry,agriculture and mining,the pollution and restoration of heavy metals in aquatic ecosystems are receiving more and more attention.The deterioration of the water environment will directly harm the health of organisms.How to deal with the heavy metal problems in wastewater is an important issue.If the magnesium hydroxide produced by industrial wastes and biological calcium carbonate?egg shells,oyster shells?from agricultural wastes can be treated as heavy metal wastewater,it not only solves the problem of heavy metal and acid pollution in water,but also can be used for industrial and agricultural wastes.New ways of comprehensive utilization.Biological calcium carbonate and magnesium hydroxide have low reactivity to certain heavy metals.Modified methods can be used to improve their adsorption performance.Among many modification methods,thermal modification is cheap,easy to operate,and has good adsorption effect after modification.So for the removal of heavy metal anions Sb?III?and cations Pb?II?in wastewater,the performance of thermal modification magnesium hydroxide and biological calcium carbonate to remove heavy metal ions and related mechanisms were studied.The main research contents and innovations are as follows:?1?For the first time,thermally modified Mg?OH?₂was used to remove Sb?III?in water system.Research through XRD,TEM and XPS showed that the Mg?OH?₂phase thermally modified at 400?has been converted to Mg O and the main removal mechanisms lie in the generation of Mg active sites,capable of coordinating Sb?III?,during the hydration process of Mg O,which will provide a nucleation center for the progressive production of Mg Sb₂O₄.As a whole,precipitate is the predominant mechanism for Mg O to remove Sb?III?.Over time,a part of Mg O is hydrated to Mg?OH?₂,and consequent chemisorption also helps to remove Sb?III?.The batch experiments indicated that the thermally modified Mg?OH?₂at 400??named 400-Mg O?exhibited superior adsorption capacity for Sb?III?.The adsorption isotherm was fitted well with the Freundlich model,and especially when the initial concentration is 15mg?L^-1,the adsorption capacity is as high as 140.1 mg?g^-1.This study shows that thermal modification temperature has a great influence on the adsorption performance of Mg?OH?₂and provided new insights into the interaction mechanism between Mg O and Sb?III?.?2?The effect of thermal modification temperature on the adsorption of Pb?II?in aqueous calcium carbonate?egg shell,oyster shell?and related mechanisms was systematically studied.XRD,SEM,FTIR,BET and other characterization methods show that the thermal modification process at 500?removes the organic functional groups on the surface of bio-calcium carbonate,resulting in a decrease in the adsorption capacity.The phase of the thermally modified bio-calcium carbonate at 700?and 900?Ca Ca O₃is converted to Ca O,so that Pb?II?in the aqueous solution is removed in the form of chemical precipitation and ion exchange.Adsorption experiments showed that the adsorption capacity of bio-calcium carbonate thermally modified at 500?for Pb?II?was about 18%lower than that of the original bio-calcium carbonate.The adsorption capacity of 900?thermally modified bio-calcium carbonate for Pb?II?was 3600.6 mg?g^-1,which is 2.5 times of the original biological calcium carbonate,and can reach kinetic balance within 15 minutes,with excellent kinetic performance.Due to the different forms of Pb?II?in different p H environments,when the amount of high-temperature thermally modified bio-calcium carbonate is too large,it will promote the dissolution of Pb?OH?₂,resulting in a decrease in adsorption capacity.Therefore,in practical application of thermally modified calcium carbonate,we should pay attention to the temperature and amount of thermal modification of the adsorbent.