Study On The Adsorption Performance For Heavy Metal Of Modificated Straw Stalk

Straw stalks as agricultural waste used in wastewater treatment had low cost,simple operation,good effect and turn waste into treasure,etc.Straw stalks might be modified to enhance the adsorption of heavy metal ion in aqueous solution.In this paper,the modification of natural straw and its characteristic had carried on the exploration,the experiment under the condition of laboratory simulation wastewater of heavy metal Cu²⁺,Pb²⁺and Cr³⁺,to explore the change of the molecular structure of straw stalk,the apparent characteristics of the specific function and heavy metal adsorption efficiency.The main experimental process and results of the study in this paper:（1）The modification methods of the straw stalk.the modification methods had been determined through times of modified experimental exploration and comparison analysis:straw stalk should be filtered through 100 mesh sieve,with 30% NaOH preprocessing about 4h,a mass fraction 5% of potassium permanganate and a mass fraction 5% of sulfuric acid mixture mixing about 1h under 80 ℃,the black modified straw stalk would be got after washing to neutral as a very good effect for removing heavy metal ions.（2）The adsorption experiment for heavy metal Cu²⁺,Pb²⁺,Cr³⁺.Static adsorption experiment of the straw stalk before and after modification was carried out respectively.Results showed that the initial concentration of heavy metals,solid-liquid ratio,pH,temperature,time and additive quantity of adsorbent were a certain degree of influence factors to the absorption effect of strawstalks.Initial concentration of 100mg/L,solidliquid ratio of 10g/L,pH was 7,the temperature was 25℃ and the adsorption time was 45 min,before and after the modification of straw,the removal rate of Cu²⁺,Pb²⁺,Cr³⁺ were57.7%,63.6%,72.2% and 99.8%,91.1%,91.45%.Modification has made the adsorption ability of straw stalk greatly enhanced on heavy metal Cu²⁺,Pb²⁺,Cr³⁺,straw adsorption kinetics had been in line with pseudo-second order model,and the adsorption isotherm had been applicabled to the Langmuir model.（3）The adsorption performance of inquiry experiment in multiple heavy metal ions hybrid system.1g modified straw stalk was added to binary and ternary blend solution with heavy metal concentration of 100 mg/L respectively.The results showed that,the Cr³⁺+Cu²⁺,Cr³⁺+Pb²⁺ binary system and Cu²⁺+Pb²⁺+Cr³⁺ ternary system,Cr³⁺ had a strong role in promoting the adsorption of Cu²⁺ and Pb²⁺,the removal rate of Cu²⁺,Pb²⁺ has been greatly improved,the removal rate of Cr³⁺ has been reduced obviously,Cu²⁺,Pb²⁺ had obvious inhibition antagonist for Cr³⁺,the sum of the adsorption for the total heavy metal ions ofstraw stalks has been obvious declined relative to a single system;There was a synergy between two ions in the binary system of Cu²⁺+Pb²⁺,the total amount of adsorption of modified straw has increased obviously.（4）The inquiry experiments of the practical application and regeneration ability of modified straw stalks.in the practical application experiment,about 100 ml solution would been respectively prepared 20,30,50,100mg?L-1 of Cu²⁺,Pb²⁺,Cr³⁺,then 1g after adsorption saturation of the adsorbent would be added,the concentration of residual Cu²⁺,Pb²⁺,Cr³⁺would been measured after been oscillated 45 min in constant temperature oscillation table,the filtered water of Chao Hu lake was used in this experiment.In regeneration ability experiment,1g after adsorption saturation of the adsorbent would be added to 0.2 mol/L HCL solution,the concentration of heavy metal in the regeneration solution has been analyzed after 30 min,acid adsorption capacity of modified straw resolution was reviewed;and the influence of the number of adsorption-parse on straw adsorption capacity was analysised.The results showed that,the modified straw stalks still had considerable adsorption ability for heavy metal ions when it was used in natural water,the adsorption quantity of Cu²⁺,Pb²⁺,Cr³⁺ was 7.14 mg.g-1,5.92 mg.g-1,6.43 mg.g-1 and removal rate was71.4%,59.2%,64.3%.The desorption rate of saturated adsorption of modified straw was around 90% with 30 ml 0.2 mol/L HCL solution,modified straw had good adsorption and regeneration for heavy metal ion Cu²⁺,Pb²⁺ and Cr³⁺.