Study On The Kinetics And Mechanism Of Pb²⁺ Adsorption In Loofah Fixed Oscillatoria Lutea

With the continuous increase of industrial production activities,heavy metal pollution in water has become more and more serious.Biosorption technology has been widely used in the adsorption of heavy metals in recent years,compared with traditional ion exchange and precipitation methods,biological adsorption method has the advantages of low investment,high efficiency,less consumption,and cancan effectively treat heavy metal ions in wastewater,etc.Among them,algae cells was rich in proteins,polysaccharides,and other substances that can bind to heavy metals on their surfaces,and have strong adsorption capacity for heavy metals,and was rich in resources and easy to cultivate.Therefore,they were a kind of biosorbent with good application prospects.Nitrogen and phosphorus were important nutrient elements for the growth of algae cells and have a significant impact on the growth and composition of algae.In this experiment,Oscillatoria lutea was selected as the research object,and the culture was optimized by changing the concentration of nitrogen and phosphorus in the medium.Oscillatoria lutea was used as a carrier to prepare immobilized Oscillatoria lutea.This was used as an adsorbent to study the immobilization before and after optimization at the reactor level.The adsorption effected and adsorption mechanism of Oscillatoria lutea on Pb²⁺,the experimental results are as follows:（1）The concentrations of nitrogen and phosphorus had a significant impact on the growth of Oscillatoria lutea.With the mass concentrations of nitrogen and phosphorus increased,the growth of Oscillatoria lutea was increasing.The optimal nitrogen and phosphorus mass concentrations were 277.68 and 35.6 mg/L.When the nitrogen and phosphorus mass concentrations increased to 555.36 and 142.7 mg/L,the growth of Oscillatoria lutea was inhibited.（2）After the optimized cultivation,the surface structure of Oscillatoria lutea were changed.Fourier transform infrared spectroscopy（FTIR）showed that the characteristic peak intensity at the carbon-carbon double bond or triple bond on the surface of Oscillatoria lutea was increased,and the NH stretching vibration peak intensity of-OH or-NH₂was decreased;scanning electron microscope（SEM）results showed that there were a lot of pores on the surface of Oscillatoria lutea,which was good for the adsorption of heavy metals.Compared with free Oscillatoria lutea,the immobilized Oscillatoria lutea entangles on the surface of the loofah to avoid its agglomeration,increaseed the contact area,and improveed the adsorption capacity.（3）The detection methods of three heavy metal ions were compared and optimized.Hydride generation-atomic fluorescence spectrometry,spectrophotometry and chemiluminescence had a good linear relationship,and the results showed that the detection limits were 0.430,1.239×10~2and 0.131μg/L,the recovery rate were 103.35%,105.78%and 97.56%,respectively,and the precision of RSD was 1.04%-1.62%,1.27%-2.26%and1.08%-1.56%,respectively.Chemiluminescence method showed the lowest detection limit and the highest recovery rate.And hydride generation-atomic fluorescence spectrometry and chemiluminescence methods were better than spectrophotometry in the accuracy and precision.Therefore,chemiluminescence was a good method selected.（4）The effects of adsorption time,solution p H and initial Pb²⁺concentration on the adsorption of Pb²⁺by immobilized Oscillatoria lutea were investigated at the reactor level.The results showed that when the adsorption time was 120 min,the p H value was 5,and the initial Pb²⁺concentration was 100 mg/g,the unit adsorption capacity of Oscillatoria lutea for Pb²⁺after optimization increasesed by 8%,and the equilibrium adsorption capacity reached the maximum.The adsorption effect was slightly better than that of unoptimized culture of Oscillatoria lutea.The qesudo-first-and qesudo-second kinetic models were fitted for the adsorption process,and the qesudo-second-level kinetic model can better react to the adsorption process;（5）FTIR,X-ray diffraction and SEM techniques were used to characterizate the adsorption mechanism of the adsorbent.During the adsorption of Pb²⁺in Oscillatoria lutea,the content of Na,Mg and K in the Oscillatoria lutea decreased,and ion exchange occurred.The groups involved in the adsorption of Pb²⁺mainly include-CH,-OH,C=C,C≡C and-NH₂and other functional groups;after the adsorption of Pb²⁺,the surface of Oscillatoria lutea had changed from smooth to rough.Changed in the concentrations of nitrogen and phosphorus in the environment would be affected the surface structure of Oscillatoria lutea.After optimizing the cultivation,Oscillatoria lutea was fixed with loofah,and the effect of adsorbing Pb²⁺was enhanced.It is an efficient,economical and green biosorption material with potential for practical application.