| Recently,the increasing emergent water pollution events has received wide attention.Water purification is the last barrier to deal with water pollution incidents.At present,two effective methods commonly used in emergency treatment are chemical precipitation and strengthening coagulation.However,there are a lot of problems within emergency treatment due to using these two kinds of technology.In this paper,cadmium was selected as the target contaminant,cheap accessible biomass material rice husk was preferred as raw material,modified rice husk has been prepared and used as adsorbent to remove cadmium when emergency pollution happens,and the several concentrations modified rice husk can cope with were given.Moreover,this research is expected to guide emergency work of water purification plant for water pollution.Firstly,by continuously optimizing the preparation conditions of modified rice husk,the best preparation conditions has been finded out,the reaction time was 60 min,the radio of rice husk and CS2 was 1:1(g/m L),the radio of rice huskand Mg SO4 was 1:1(g/m L),and the temperature was 20?.And The modified rice husk was measured through EA(elemental analysis)?BET?SEM?EDS?FT-IR.Compared with the raw rice husk,the infrared spectrogram of modified rice husk appeared S-S peak(470 cm-1),C-S absorption peak(796cm-1),C=S peak(1203cm-1),the result proved that the R-O-CS-S functional group was successfully grafted to the surface of the rice husk.The surface topography of rice husk before and after modification obviously changed,and metals(sodium,magnesium,and cadmium)were detected in the surface of rice husks after the adsorption.Besides,the contents of C and S elements of modified rice husk rose significantly,while the contents of N and H decreased.Compared with the original rice husk,the p Hpzc raised from 6.28 to 6.89,and the surface area of modified rice husk was nearly 36 times greater than original rice husk.The adsorption mechanism of modified rice husk was studied t hrough experiments of static adsorption.The adsorption capacity of modified rice husk to cadmium was 124.35mg/g at 20?.The results showed that the adsorpt process of cadmium ions in modified rice husk follows the Langmuir adsorption isotherm model and the pseudo-second order model.From the results of adsorption fitting,it was a monolayer adsorption and was controlled by chemical adsorption.In addition,it was proved that the adsorption of cadmium ions in modified rice husk includ es both the ion exchange and chelating coordination.Finally,the adsorption capacity of modified rice husk to remove Cd(?)was determined experimentally.The experimental results revealed that the maximum dosages of the adsorbent were 150 mg/L and 300mg/L,respectively,when the turbidity was less than 3NTU by naturally settling or adding coagulant to strengthen the sedimentation.Corresponding to these two situations,the allowable maximum concentrations of cadmium were 0.15mg/L and 0.2mg/L.Considering the competitive adsorption of common cations in water,the maximum concentration of cadmium can be reduced from 0.2 mg/L to 0.125mg/L,while the Na(?),K(?),Mg(?)and Ca(?)ions coexist in water.In order to know the allowable concentrations of cadmium and lead in the case of co-existence,a series of experiments were done.When the adsorbent dosage is 300mg/L,the results showed that the maximum concentrations of cadmium and lead were 0.2mg/L and 0.5mg/L.In this study,the modified rice husk was applied to the cadmium pollution emergency treatment of the water supply plant,and it has the advantages of high adsorption capacity,fast and stable adsorption.This research has a great practical significance. |
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