Zeolite nanoparticles containing composites production and characterization of membranes

The requirement for the reduced unit size, process time and energy leads to design and develop more compact and functional materials. Conventional processes for the removal of heavy metals in the industrial effluents consist of pre-filtration of the suspended particles and metal adsorptions which are carried out by two separated units. In this study, two processes were coupled via zeolite nanoparticles impregnated polysulfone (PSf) membrane which was used for the removal of lead and nickel cations in synthetically prepared solutions. The results obtained from X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis revealed that the synthesized zeolite nanoparticles using conventional hydrothermal method (60˚C and 4 days) was pure NaX with ultrafine and uniform particle sizes around 170 nm and Si/Al ratio of 1.24. Batch adsorption studies at 25˚C revealed that, NaX nanoparticles have high affinities against lead, nickel cations. Asymmetric membranes were fabricated with pore radius changed from 15 to 40 nm when the amount of NaX was increased to 10w% in the casting solution. The increase in pore sizes and hydrophilicity with the addition of NaX caused to increase hydraulic water permeabilities, Lp, from 23 to 45 L/m2.h.bar at which 30 seconds of evaporation time was applied for the fabrication of the membranes. Extending or neglecting the evaporation periods as 300 or 0 second during membrane formations altered the porous structure of the membranes significantly and hence Lp values were minimized as 0.7 L/m2.h.bar and maximized as 57 L/m2.h.bar for the former (PSf10-300) and latter (PSf10-0) membrane architectures respectively. Filtration of metal ion solutions through PSf10-0 membranes under 1 bar transmembrane pressure for 60 min revealed that the sorption capacity of the membranes were increased from 359 to 681 mg/g as the initial lead concentrations were increased from 50 to 500 ppm respectively. During filtration of nickel solutions, equilibrium sorption value was almost achieved as 122 mg/g at 200 ppm initial feed solution. Equilibrium sorption isotherms were best fitted to Langmuir model and the maximum equilibrium amount on the solid phase were predicted as 790 and 157 mg/g for the lead and nickel ions respectively. Cross flow filtration experiments were carried out at different pressures, initial metal concentrations and temperatures and it was achieved that under low pressures, temperatures and initial metal concentrations, the permeate concentrations are close to the limit values provided by environmental and health organizations. Experimental data were regressed by the multiple variables rational model function and successfully described the response function.