Study On The Biosorption Of Dyes And Antibiotics By Ulva Lactuca Biomass

Green tide in the Yellow Sea of China has become a normal marine ecological disaster,which has caused serious impacts on the ecological environment,but there are still certain limitations in the treatment and application of large-scale macroalgae.In addition,the pollution caused by dye and antibiotic wastewater in our country also has adverse effects on human health and the environment.Therefore,this article chooses the macroalgae Ulva lactuca as the adsorbent,and uses dyes(methylene blue,congo red,metanil yellow,orange G)and antibiotics(norfloxacin,chloramphenicol,penicillin)as adsorbates.Various preparation methods of U.lactuca biomass(powder,biochar,activated carbon),and physical and chemical analysis of SEM,FTIR,XRD,BET and other physical and chemical properties;secondly,the factors affecting the adsorption of dyes and antibiotics(adsorbent dosage,ion concentration,oscillation rate,pH),It also discusses the adsorption mechanism through kinetics,isothermal adsorption and thermodynamics.The aims are providing theoretical references for wastewater treatment and the resource utilization of green macroalgae in the future.The main findings are as follows:The physical and chemical properties of three U.lactuca biomass prepared are different.The surface pore structure of U.lactuca powder is very small,while U.lactuca biochar and activated carbon are rich in pore structure,belonging to the microporous-mesoporous composite type,and the specific surface area and total pore volume of activated carbon are larger than that of biochar,which is more conducive to adsorption.In addition,compared with U.lactuca powder,the functional groups on the surface of U.lactuca biochar and activated carbon are reduced.U.lactuca powder has O-H,N-H,C-H,C=O,C-C,C-O-C,S-O bonds,etc.The surface of U.lactuca biochar lacks C-H bond,U.lactuca activated carbon lacks S-O bond.The number or position of the absorption peaks of the three U.lactuca biomass changed before and after adsorption,indicating that a variety of functional groups participated in the adsorption reaction.The adsorption effect of U.lactuca on the four dyes is:methylene blue>congo red>metanil yellow>orange G.Among the three U.lactuca biomass,the adsorption capacity of U.lactuca activated carbon for methylene blue(476.79 mg/g)is slightly higher than that of U.lactuca powder(453.36 mg/g),and U.lactuca biochar is the lowest at 306.80 mg/g.This adsorption difference is affected by different preparation methods and temperatures.For U.lactuca biochar,the high-temperature pyrolysis method is far superior to the hydrothermal treatment method,and the adsorption effect of biochar prepared at 500℃ pyrolysis temperature is better than 400℃ and 600℃.For U.lactuca activated carbon,KOH activation method is better than H3PO4 and FeCl3 activation method.The adsorption effect of U.lactuca on methylene blue is affected by the amount of adsorbent,ion concentration,and shaking rate.The best adsorption conditions are:U.lactuca mass concentration 0.2 g/L,ion concentration 0 g/L,and shaking rate 150 r/min.The results of the kinetic study show that the quasi-second-order kinetics can better describe the adsorption process of U.lactuca for methylene blue,and the adsorption rate is mainly affected by the combination of surface functional groups and methylene blue molecules.The adsorption isotherm results show that the whole adsorption process of U.lactuca powder for methylene blue is consistent with the Langmuir model.It belongs to monolayer adsorption,with the saturated adsorption capacity of 909.09 mg/g,which has a higher market than other reported biosorbents.In addition,the thermodynamic results show that the adsorption of methylene blue by U.lactuca is a spontaneous and endothermic reaction,and there exists certain desorption reaction during the reaction process.The adsorption results of three kinds of U.lactuca biomass on three antibiotics also show that the adsorption capacity of activated carbon is the highest,followed by powder,and biochar is the lowest.Among them,for U.lactuca biochar,the biochar prepared at a pyrolysis temperature of 400℃ has the best adsorption effect on norfloxacin and chloramphenicol,while the adsorption effect of biochar prepared at a pyrolysis temperature of 500℃ on penicillin is better than 400℃ and 600℃,but the effects are not much different.For U.lactuca activated carbon,KOH activation method is also better than H3PO4 activation method.The adsorption effects of U.lactuca on norfloxacin,chloramphenicol,and penicillin are all affected by the pH and ion concentration of the adsorption system.The best adsorption conditions for the three antibiotics are:pH 6,ion concentration 0 g/L.The kinetic studies showed that the adsorption of U.lactuca to the three antibiotics all accorded with the pseudo-second-order kinetic equation.And adsorptions of three antibiotics are consistent with the Freundlich model,which is a multi-molecular layer adsorption process.The internal adsorption is carried out at the same time as the surface adsorption.The saturated adsorption capacities are 976.17 mg/g,1421.54 mg/g and 1875.77 mg/g.The adsorption effects are also higher than other adsorbents reported in the relevant literature.In addition,the thermodynamic results show that the adsorption reactions of these three antibiotics are all spontaneous and endothermic reactions,and there exists certain desorption reaction during the reaction process.