Impact of poly(vinyl alcohol) adsorption on the surface characteristics of mixed oxide Mn x O y –SiO2

Adsorption (2016) 22:417–423 DOI 10.1007/s10450-015-9696-2 Impact of poly(vinyl alcohol) adsorption on the surface characteristics of mixed oxide MnxOy–SiO2 M. Wiśniewska1 • V. Bogatyrov2 • I. Ostolska1 • K. Szewczuk-Karpisz1 • K. Terpiłowski3 • A. Nosal-Wiercińska4 Received: 21 August 2015 / Revised: 15 September 2015 / Accepted: 18 September 2015 / Published online: 22 September 2015 Ó The Author(s) 2015. This article is published with open access at Springerlink.com Abstract The poly(vinyl alcohol) (PVA) influence on the adsorption and electrokinetic properties of the mixed oxide MnxOy–SiO2/polymer solution system was examined. Three oxides differing with the MnxOy contents were applied (0.2; 1 and 3 mmol/g SiO2, respectively). The PVA with the molecular weight 100 kDa was characterized with the acetate groups content equal to 14 %. Adsorption, solid surface charge and zeta potential measurements were made as a function of solution pH (3–10). The obtained results showed that the PVA adsorption amount strongly depends on not only the solution pH, but also manganese oxide content on the mixed oxide surface. The higher solution pH value (or MnxOy content) is, the higher polymer adsorption is obtained. The PVA addition to the solid suspension causes minimal changes of the mixed oxide surface charge density, whereas the zeta potential of solid particles increases significantly in the polymer presence. & M. Wiśniewska 1 Department of Radiochemistry and Colloids Chemistry, Faculty of Chemistry, Maria Curie-Sklodowska University, M. Curie-Sklodowska Sq. 3, 20-031 Lublin, Poland 2 Chuiko Institute of Surface Chemistry, General Naumov Street 17, Kiev 03164, Ukraine 3 Department of Physical Chemistry – Interfacial Phenomena, Faculty of Chemistry, Maria Curie-Sklodowska University, M. Curie-Sklodowska Sq. 3, 20-031 Lublin, Poland 4 Department of Analytical Chemistry and Instrumental Analysis, Faculty of Chemistry, Maria Curie-Sklodowska University, M. Curie-Sklodowska Sq. 3, 20-031 Lublin, Poland Keywords Mixed oxide
MnxOy–SiO2
Poly(vinyl alcohol) adsorption
Zeta potential
Solid surface charge density 1 Introduction The application possibilities of metal oxides (including manganese oxides) in various branches of industry and ecology are large. For example MnO is commonly used as a component of fertilizers and food additives. On the other hand, MnO2 is a component of dry-cell and zinc–carbon batteries. Both solids also find application as inorganic pigments in ceramics and glassmaking. Their other usages include applications in catalysis (synthesis of allyl alcohols, CO oxidation), paints production, bleaching tallow and textile printing. A very important aspect from the environmental point of view is the use of metal oxides obtained from removal of hazardous and undesirable substances from wastewaters. Recently manganese oxide coated zeolite was applied to remove Mn2? from aqueous solutions (Taffarel and Rubio 2010). Manganese dioxide was also used as an adsorbent for phosphate in seawater (Yao and Millero 1996). Copper, cadmium, lead, zinc, iron, selenium and arsenic removal by the use of manganese oxide (both synthetic and natural minerals) was also examined (Kang et al. 2010; Puppa et al. 2013; Ergül et al. 2014; Demirkiran 2015). However, metal oxides are often characterized by small specific surface area and inadequate stability of their aqueous suspension. In such a case, solid surface modification is necessary. Of great variety of techniques; plasma modification (Kuraica et al. 2003; Punga and Borcia 2013), adsorption of different low- and high-molecular compounds (Chibowski et al. 2010; Nosal-Wiercińska 2012, 2013; Wiśniewska et al. 2013a; Nosal-Wiercińska 2014) and 123 418 Adsorption (2016) 22:417–423 Table 1 MnxOy–SiO2 mixed oxides characteristics Symbol MnxOy content (mmol MnxOy/g SiO2) BET surface area (m2/g) Pores volume (cm3/g) pHpzc of MnxOy–SiO2/ NaCl systems 02 Mn–SiO2 0.2 306 0.934 6.88 1 Mn–SiO2 1 264 1.008 7.75 3 Mn–SiO2 3 186 1.115 8.01 Kadajji and Betageri 2011; Karimi and Navidbakhsh 2014). Polyvinyl alcohol is also used in food industry as an agent to retain satisfactory taste, texture and quality of the food (Gupta and Arora 2011). The monomer of PVA–vinyl alcohol is very unstable and immediately undergoes isomerization to acetaldehyde. For this reason PVA is not prepared by polymerization of the corresponding monomer but in the polymerization process of vinyl acetate. Obtained polyvinyl acetate is converted to the PVA by the hydrolysis of its acetate groups to hydroxyl ones. synthesis of mixed oxides (Maliyekkal et al. 2006; Wu et al. 2010) acquired the most significant importance. Appropriate modification leads to obtaining solids of the properties desired in various ecological and technological processes (Kaźmierczak et al. 2013; Nowicki et al. 2014, 2015a, b). Nanocomposites with nanosilica A-380 (Degussa) and grafted manganese oxide were prepared using manganese acetate—Mn(CH3COO)2
4H2O. The obtained aqueous dispersion was treated at 600 °C. MnxOy–SiO2 mixed oxides (varying in MnxOy content) obtained in such a way exhibit different surface characteristics and adsorption affinity for macromolecular compounds. They were also characterized by very large surface area. Different structure and surface properties of mixed oxides in comparison to simple oxides can change nature of interactions between the macromolecules and the solid surface. Thus, these substances can be used as effective adsorbents in many technological processes. In the present study the mechanism of poly(vinyl alcohol) (PVA) adsorption on the surface of MnxOy–SiO2 was investigated. This was done based on the results of measurements: spectrophotometric (determination of the adsorbed amount of the polymer on the solid surface), potentiometric titration (determination of the surface charge density of mixed oxide in the absence and presence of the PVA) and electrokinetic (zeta potential determination of MnxOy–SiO2 particles covered and not with polymeric layers). As follows from the obtained results the solution pH (in the range 3–10) affects the adsorption mechanism of PVA on the surface of mixed oxide. The polymer presence also has the effect on the structure of electrical double layers (edl) formed around solid particles. The PVA was chosen for studies due to its extensive use in many branches of industry. PVA finds a wide application in the production of adhesives, coatings, medicines, paints, paper, oils, fibers and hydrogels (Hassan and Peppas 2000; HC OH CH 2 CH O C 123 H CH 2 O CH3 n + + 2 Experimental 2.1 Materials Three samples of mixed oxides, consisting of silica (SiO2) and manganese oxide (MnxOy), were used as adsorbents. All solid samples were prepared in the Institute of Surface Chemistry of the National Academy of Sciences of Ukraine in Kiev. Mixed oxides were characterized by different MnxOy contents, i.e. (...truncated)