Heavy Metals And Organic Compounds Biosorption By A Novel Exopolysaccharide From The Deep-sea Mesophilic Bacterium Wangia Profunda (SM-A87)

With the acceleration of industrialization process,environmental pollution has become much more serious and one of the most important issues for sewage treatment and rehabilitation of contaminated soil.Since solid-liquid adsorption is one of the common methods of wastewater treatment,it is important to study the adsorption behavior of pollutants and develop efficient,low-cost sorbents.Wangia profunda(SM-A87),a mesophilic bacterium isolated from deep-sea sediment samples taken from the southern Okinawa at a depth of 1245 m,can cecrets a lot of sticky exopolysaccharide.It is anticipate that SM-A87 EPS be a novel biosorbent for wastewater treatment for it has strong interactions with heavy metals and organic materials.1.SEM and TEM images showed the surface of SM-A87 EPS was irregular multilayer micro-fibriform.The temperature of thermal decomposition process, average particle size and specific surface area of the EPS are 275℃,100 nm and 673 m²/g,respectively.The main elements of SM-A87 EPS are C,H,O and N, while the main functional groups are hydroxyl and carboxyl groups,with the density of surface hydroxyl groups 40 mmol/g.Zeta potential of the EPS is negatively increased as pH increased when pH is higher than 3.2.SM-A87 EPS has strong adsorption capacity of Pb(â…¡),Cu(â…¡) and Cd(â…¡), observably higher than some commen-used adsorbent(bentonite,chitin and chitosan),especially in the seawater medium.The order of biosorption capacity of different metals onto SM-A87 EPS was:Pb(â…¡)＞Cu(â…¡)＞Cd(â…¡).The sorption kinetics can be described by pseudo-second order kinetic model.The biosorption data of Pb(â…¡) and Cu(â…¡) fit Langmuir isotherm well,while the biosorption data of Cd(â…¡) was favorable for the Freundlich isotherm.The pH value,temperature and salts(NaCl,KCl,MgCl₂ and CaCl₂) can greatly decrease the biosorption properties of SM-A87 EPS for heavy metal.The maximum adsorption capacity of the tri-metal could all reach in the mild acid pH and 30℃.In the Pb(â…¡) and Cu(â…¡) removal process,the chemical and electric bonding coexist,while the electric bonding plays a main role.3.The sorption amount of p-nitrophenol and p-nitroaniline by SM-A87 EPS is high and the order of biosorption capacity of p-nitroaniline was higher than p-nitrophenol.The sorption kinetics can be well described by pseudo-second order kinetic model and the biosorption data fit Langmuir isotherm well.The pH value and temperature had remarkable influence on the biosorption properties of SM-A87 EPS for organics removal.The maximum adsorption capacity of organics onto EPS could reach in the mild acid pH and 30℃.4.SM-A87 EPS has great specific surface area,rich hydroxyl and carboxyl groups,and strong negative electric,which makes its strong adsorbtion capacity. All the results show that SM-A87 EPS is novel biosorbent that will be practically used in the future.