چكيده به لاتين
Every day, large quantities of dangerous industrial wastewater containing toxic substances such as heavy metal ions are released in the environment. These heavy metal ions need to be separated from wastewater to reduce their destructive effects on nature. In this study, electrospun nano-porous polystyrene fibers cation exchange membrane (E-PM) was made by sulphonation of electrospun polystyrene fibers to adsorb heavy metal ions from wastewater. In order to increase the efficiency of the E-PM and increase its specific surface area, porous fibers (PF) has been developed by changing the spinning environment (temperature in the range of 25 - 45 °C and humidity in the range of 30 - 70 %) and adding different levels of nano silica to the polymeric solution needed for spinning ( 0 – 4 %w); To find out the optimum level of each for having the highest specific area, an experimental design was made by Response Surface Method. The SEM images taken from the fibers surfaces have well established the nanopores and nano silica existance on the surface of the fibers. The results of the BET test and processing by Design Expert sofware showed that the highest specific area happens at temperature of 30 °C, relative humidity of 65 % and 2.3 %w of nano-silica which has the specific area of 48.15 m2/gr. The PF with the highest specific area were treated by 97 % sulfuric acid to add agent groups to their surfaces for ion-exchange process. The results of the FTIR test confirmed this addition. In order to evaluate the performance of E-PM in adsorption of nickel metal ions from aqueous solution, an experimental design was made by Response Surface Method using the variables of adsorbent (A) (in the range of 0.005 - 0.025 gr), absorbent concentration (C) (In the range 100 - 300 ppm), pH (in the range of 3 - 11) and contact time (T) (in the range of 30 - 90 min). The results of the Atomic Absorption Spectroscopy test on the adsorbed samples and processing with Design Expert software showed that the maximum adsorption happens at A = 0.015 gr, C = 100 ppm, pH = 7 and T = 60 min with the adsorption of 99.9 % . In order to compare the performance of the E-PM with non-porous electrospun polystyrene fibers cation exchange membrane (E-M) (which happens in electrospinning process at room temperature, room humidity with no nano silica in polymeric solution), ion exchange capacity and adsorption rate have been investigated. The ion exchange capacity and adsorption rate in the conditions of A = 0.015 gr, C = 200 ppm, pH = 7 and T = 60 min for E-PM were 3.9 meq/gr and 99.5 %, respectively, and for E-M were 3.5 meq / gr and 90 % that means a higher performance of E-PM to E-M for nickel ion adsorption.
