| In recent years,in view of the basin sudden heavy metals and organic matter,the sediment in the water can remove heavy metals and organics.In this experiment,turbidity was used as indicator and choose the soil of Guangzhou Dongjiang river?a?,Taizhou Yangtze river?b?and Nantong Yangtze river?c?to similate the turbidity and study the influence of turbidity?50 NTU650 NTU?on the removal of heavy metals cadmium,lead and arsenic at room temperature?25??and low temperature?5??.Cadmium is one of the most harmful five heavy metals,so it is needed to find an economical adsorbent to treat cadmium-containing wastewater.The distribution area of red soil in China is more than 2 million square kilometers,and it has been proved to be a potential adsorbent except Cd2+.Red soil along the eastern coast of Guangzhou was selected as the raw material for the experiment,XRF,BET,particle size analysis,adsorption capacity and other data were measured,and pH,ionic strength,co-existing ions,temperature and adsorption time on the adsorption effect was studied.SEM,EDS,FTIR characterization methods and thermodynamics?kinetics were used to analyze the adsorption mechanism.The adsorption properties of sediment from Taizhou and Nantong were studied.The results showed that:?1?the removal effect of the simulated turbidity on heavy metal cadmium,lead and arsenic was lead?30?cadmium>arsenic.?2?turbidity is linearly correlated with sediment content,and the higher the sediment content,the greater the turbidity value.?3?there is a linear relationship between turbidity and the maximum concentrations of Cd2+,Pb2+and As???that can meet the standard.?4?Normal temperature?25??can remove higher initial heavy metal concentration up to drinking water standard than low temperature?5??.?5?at the same turbidity,there is little difference in the removal effect of heavy metals from the same sediment,which can provide data support for sudden heavy metal events in the basin.The size of red soil used in the experiment was mainly distributed between10200?m,with a specific surface area of 16.41 m2·g-11 and an adsorption capacity of about 2.10 mg·g-1.Study found that the initial solution pH,ionic strength,coexisting ions,slurry concentration,environment temperature,adsorption time,Zeta potential on the adsorption of Cd2+have great influence.when pH<4,mainly rely on the carboxyl of protonation and deprotonation,when 4<pH<8,mainly through ion exchange and outer-sphere surface complexation,pH>8,inner-sphere surface complexation is the main sorption mechanism.Langmuir adsorption isothermal model and quasi-secondary kinetic model fit well for red soil adsorption Cd2+,indicating that the reaction mechanism was mainly monolayer chemisorption.Thermodynamic parameters??H,?S,?G?show that the adsorption is a spontaneous endothermic process.Through FTIR analysis,it can be seen that the main role of adsorption process is silicon hydroxyl and carboxyl in organic matter.The sediment in Nantong and Taizhou were all monolayer chemical adsorption. |
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