Study On Copper Ion/lanthanum Ion Doped Calcium Alginate-based Hydrogel Filtration Membrane And Its Separation Performance

Generally,organic solvents are used to prepare polymer-based membranes,but they tend to cause environmental pollution;while calcium alginate(CaAlg)hydrogel filtration membranes prepared with water as solvent have low strength and are not salt-tolerant.In this paper,Cu²⁺/CaAlg and La³⁺/CaAlg hydrogel filtration membranes were prepared by using copper ion and lanthanum ion which has a stronger affinity for calcium ion and alginate secondary cross-linking calcium alginate(CaAlg)hydrogel filtration membrane,and applied to the treatment of printing and dyeing wastewater.In order to realize the separation of dye and inorganic salt ions,the dye rejection,desalination effect,influencing factors of filtration performance and long-term stability of membrane are explored.The main conclusions are as follows:(1)The Cu²⁺/CaAlg hydrogel filtration membrane exhibits excellent separation performance in the treatment of printing and dyeing wastewater.At 0.1 MPa,the rejection rates of Brilliant blue G and Direct black 38 are both close to 100%,while the salt rejection rate is less than 10.0%.The pure water flux of Cu²⁺/CaAlg filtration membrane is 65 L·m^-2·h^-1.Without cleaning,the pure water flux only is only reduced by 15%after three alternating cycles of pure water and yeast suspension,indicating that the membrane has good anti-fouling performance.The Cu²⁺/CaAlg filtration membrane has good mechanical properties and antibacterial properties.The density distribution and pore size distribution of CaAlg membrane and Cu²⁺/CaAlg membrane were studied by molecular dynamics simulation.The simulation results show that the density of CaAlg membrane and Cu²⁺/CaAlg membrane does not change significantly.After doping with copper ions,the average pore size increases.(2)The CaAlg membrane was cross-linked with LaCl₃·7H₂O aqueous solution to prepare the lanthanum ion doped calcium alginate hydrogel(La³⁺/CaAlg)filtration membrane.The membrane properties were characterized by SEM,AFM,water contact angle and tensile strength.The resulting membrane has a super-hydrophilic surface and excellent mechanical stability.The rejection rate of Brilliant blue G,Direct black 38,Direct red 23 and Congo red is above 95%and the salt rejection rate is less than 12%.The flux and rejection rate of La³⁺/CaAlg filtration membrane are very stable and can be used to treat dye wastewater with high salinity.