8-hidroksikinolin içeren polimer içerikli membranların karakterizasyonu ve metal tutunumu = Characterization and metal capture of polymer inclusion membranes containing 8-hydroxyquinoline

Abstract

Environmental pollution has adverse effects not only on human health but also on a country's economy. The need for clean water is increasing due to population growth and industrial production. Recent climatic irregularities have also increased the need for clean water resources and their importance. The presence of metal ions in water is one of the most important reasons for environmental pollution. Metals in industrial wastewater are the biggest pollutant sources. Wastewater must be discharged before being discharged into the environment. For this purpose, adsorption is an effective, cheap and easily applicable method. Among membrane technologies, polymer-containing membranes (PIMs) have had remarkable applications in recent years. Polymer inclusion membranes were used in this study. Polyvinyl Chloride (PVC) is a widely used synthetic plastic polymer obtained by the polymerization of chlorine and ethylene. It has high mechanical and chemical resistance and is a good electrical insulator. Additionally, it is cost-effective, long-lasting, and recyclable, making it attractive. Due to its wide range of applications and durability, PVC has become an indispensable material in modern industry and daily life. When preparing a polymer inclusion membrane from PVC, a softer material is obtained by adding plasticizer. Adsorption is the process of attaching components in the liquid or gas phase to a solid surface. The use of polymeric membranes in processes for the separation of metals has developed. Polymeric membranes are thin film structures designed for various applications. These membranes are effectively used in adsorption processes due to their high selectivity and permeability properties. They function as adsorbent materials due to their porous structures and chemical properties. Thanks to their large surface areas and pore sizes and distributions, they enable selective adsorption of certain molecules. They are effective materials offering significant advantages in adsorption processes. Due to their high surface area, adjustable porosity, chemical resistance, and mechanical flexibility, they are used in various industrial and environmental applications. It has wide usage areas in water and wastewater treatment and separation of heavy metals. Membranes were prepared by solution casting method using polymer support, polyvinyl chloride (PVC), solvent tetrahydrofuran (THF) and 2-nitrophenyl-pentyl ether (2-NPPE) as plasticizer. In the study, 8-Hydroxyquinoline, a chelating agent in a polymeric membrane, was used to effectively remove metals from aqueous solutions. 8-Hydroxyquinoline, also known as 8HQ, is a planar, small molecule with a lipophilic effect. It is a versatile quinoline derivative with many applications such as chemosensors for metal extraction and protection in the wood, paper and textile industries of products. They are also useful in agriculture as pesticides, insecticides and fungicides. Due to its remarkable coordination ability and metal recognition properties, 8HQ is an essential tool for analytical and separation purposes. 8HQ and its derivatives (HQs) are considered a fundamental class of transition element chelating agents from N- and O-donor ligand clusters and show high extractability for all metal ions. In this study, metals in aqueous solutions were effectively retained by membranes containing 8-HQ. Aqueous solutions of four metal cations at a concentration of 100 mg/L and a pH of 4, 5, and 6 were prepared for the analysis. The solution pH was adjusted with sodium acetate buffer solution. Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES) was used to measure the adsorption of Cu, Zn, Co, and Ni ions onto a polymeric membrane. Cu, Ni and Zn ions were removed from the aqueous solution by adsorption on the polymer-containing membrane. Among these metals, 8-Hydroxyquinoline showed its best adsorption on nickel metal. Membrane characterization was carried out by FTIR, XRD and SEM, SEM-EDS analyses. The membranes were analyzed and characterized in terms of surface morphologies before and after metal adsorption. It was determined as a result of XRD analysis that the membrane had an amorphous structure before and after adsorption and that its structure did not change. In the SEM-EDS image of the membrane before adsorption, it is seen that there are no other ions other than carbon, oxygen and chlorine in the membrane content. After adsorption of the membrane, the presence of metal was detected in SEM-EDS images. The surface morphology of the membrane, the pore structure became irregular after adsorption and the surface smoothness decreased. SEM images after adsorption show that the surface morphology of the membrane is significantly affected. Differential scanning calorimetry (DSC) was used to investigate the thermal properties of the membranes. The measurements (DSC, NETZSCH brand) were carried out in an Al pan, in a perforated lid, in an N2 atmosphere, with a scanning speed of 10 °C per minute, in the temperature range of 25–500 °C. The results were recorded and analyzed. The measurements were made as a service purchase from Sakarya University Research Development Application and Research Center (SARGEM). 2 ± 0.2 mg cut samples were tested in an aluminum pan in a nitrogen (N2) atmosphere with a 100 ml/min flow rate. The samples were initially heated to 400/500 °C at a rate of 10 °C/min to remove the thermal history of the disks and then cooled to 40 °C at the same rate. Then, the samples were reheated toatat 400/500 °C at the same rate of increase. Based on the thermal analysis results, pure PVC exhibited three weight losses in the TG curve. In the temperature range of 39 to 218°C, the mass loss observed in the membrane inclusion HQ is attributed to the loss of both adsorbed water and 8-HQ molecules. The TG curve in a synthetic nitrogen atmosphere showed two mass loss steps. The DSC analysis revealed two combustion reactions in the pure PVC membrane, occurring at 390 °C and 456 °C respectively. In the DSC curve of the membrane containing HQ, both endothermic and exothermic (combustion) peaks were observed. In order to examine the resistance of the obtained membranes to acid and base; membranes were kept in 0.1 M HCl, 0.1 M NaOH and 0.1 M NH3 solutions for one week. No breakup, wear and color change was observed at the end of the period. As a result, the combination of polymeric membranes and 8-hydroxyquinoline stands out as an effective method for removing metal ions from aqueous solutions. The integration of adsorption and polymeric membranes continues to be an important research area for future clean technologies and sustainable solutions.