The Applied Basic Research On The Leaf And Stem Of Jerusalem Artichokes For Treating Heavy Metal Wastewater

This work was financially supported by National Key TechnologyR&D Program of China （No.2007BAB18808）.A new type of biomas sadsorbent （JALS） was prepared from the leaf and stem of Jerusalemartichokes through si mple physical treatment, Its advantages wer eenvironmentally friendly, low cost, etc, and its characteristics andadsorption capacity of Cu²⁺, Pb²⁺, Zn²⁺, Cr³⁺, Cd²⁺and Ag⁺werestudied. The results were showed as follows:The BET surface area of JALS is1.4461m2/g, and the particle sizeof JALS used in this study was in a range between1and480μ minclusive of two maxima at about45and250μm, respectively. Theelements, such as Cu²⁺, Pb²⁺, Zn²⁺, Cr³⁺, Cd²⁺and Ag⁺were not detectedin this ma terial, which contains a certain a mount of K+,Ca2+,Mg2+. TheIR results indicated the presence of functional groups, such as Carboxyland hydroxyl. The pHz p cand decomposition temperature of the JALSwere2,258℃， respectively.Biosorption of heavy metal ions (Cu²⁺, Pb²⁺, Zn²⁺, Cr³⁺, Cd²⁺andAg⁺) from aqueous solution by the JALS in single metal ion system:when the Experi mental conditions were set as follows, the initial metalion concentrations （C0） for Cu²⁺, Pb²⁺, Zn²⁺, Cr³⁺, Cd²⁺and Ag⁺were5,20,10,20,10and10mg/L, respectively; Adsorbent dosages for Cu²⁺,Pb²⁺, Zn²⁺, Cr³⁺, Cd²⁺and Ag⁺were0.5,0.3,0.5,0.1,0.3and1g,respectively, the reaction time was24h, and the temperature was25℃,the pH value of the solution varied from1to6, the results of theremoval efficiency for Cu²⁺, Pb²⁺, Zn²⁺and Cr³⁺, Cd²⁺, Ag⁺were0.3%⁸1%,3.8%⁹6.1%,0.8%⁸4.9%,9.2%⁸8.7%,6.7%⁹6%,15.9%⁹6.3%; when the dosage was changed from0.1⁰.7g,0.1¹.3g,0.1¹.3g,0.03¹.3g,0.09⁰.9g,0.01³g and0.1¹.1g for Cu²⁺, Pb²⁺,Zn²⁺and Cr³⁺, Cd²⁺, Ag⁺, respectively, the removal efficiency for Cu²⁺,Pb²⁺, Zn²⁺and Cr³⁺, Cd²⁺, Ag⁺were77.9%⁸2.6%,68.23%⁹4.8%,74.7%⁸7.6%,31.3%⁷9%,60.4%⁹5.7%,34.8%⁹6.56%, the optimum dosage for Cu2+, Pb²⁺, Zn²⁺and Cr³⁺, Cd²⁺, Ag⁺was0.5g,0.3g,0.5g,0.1g,0.3g and1g, respectively; Kinetic experiments in thesingle-metal system revealed very rapid re moval rates of metal ions,with about90%of the total adsorption occurring within10-60min.followed the pseudo second order model well. The processes werespontaneous, except for Cr³⁺, whose adsorption process was notspontaneous until the temperature was about room temperature.Experi mental data for each metal ion were well-described by theLangmuir adsorption isotherm, and the maxi mu m adsorption capacitiesof the JALS for Cu2+, Pb²⁺, Zn²⁺, Cr³⁺, Cd²⁺a nd Ag⁺were27.79mg/g,37.25mg/g,25mg/g,123.24mg/g,34.69mg/g,23.95mg/g,respectively;Biosorption of heavy metal ions (Cu2+, Pb²⁺, Zn²⁺, Cr³⁺, Cd²⁺andAg⁺) from aqueous solution by the JALS in multiple-metal ion systems:The adsorption of metal ions on the JALS has been found to beconcentration, pH, contact time, adsorbent dose and temperaturedependent. In multiple-metal systems, a decrease in adsorptioncapacities and isother m constants was observed, showing preference ofadsorption in the order of Pb²⁺>Cu2+>Zn²⁺, Ag⁺>Cr³⁺>Cd²⁺, and kineticstudies indicated that the pseudo-second order was the best fit.Experi mental data for each metal ion were well-described by theLangmuir adsorption isotherm.Combined with the JASL’s adsorption capacity, physical andche mi calharacteristics, The mechanism of Cu2+, Pb²⁺, Zn²⁺and Cr³⁺,Cd²⁺, Ag⁺adsorption from aqueous solutions on the JALS wasdiscussed, the results indi cated that ion exchange was found to be theprimary mechanism of adsorption. Because of t he JALS’s surface wasrough and contained many gullies, physical adsorption also participatedin the adsorption process. The uptake trend was related to theelectronegativities and stability constants of the metal-ion hydroxides.The metals with the highest electronegativity value or the loweststability constants of the metal-ion hydroxides showed a greaterinhibitoryeffectonthe biosorption of other metal ions in the multiple-component syste ms. The regeneration experiments showedthat the adsorbent could be regenerated by0.1mol/L HNO3, and reusedat least ten cycles until significant decrease occurred in adsorptioncapacity. The TGA analysis indicated that the JALS’s loss ratio was80%, and its volume rate was1/12.From the research it was found that there was a potential in usingthe leaf and stem of Jerusalem artichokes as an adsorbent for heavymetal removal, and it could be used as an immediate response to toxicupset caused by heavy metals in a biological wastewater treatment plant,and it also provides a idea how to add the value of Jerusalem artichokes...