High surface area mesoporous titanium–zirconium oxide nanofibrous web: a heavy metal ion adsorbent

Abstract

A mixed titanium-zirconium (Ti : Zr ¼ 2 : 1 atomic ratio) oxide non-woven nanofibrous web was prepared by using an electrospinning technique followed by thermal treatment. A hydrocarbon surfactant was incorporated into the electrospinning solution and was pyrolysed during heating. The surfactant acted as a structure-directing agent to create intra-fibre pores, and significantly increased the surface area of the fibres, thereby maximising the number of sites for further surface modification as well as heavy metal ion adsorption. The high surface area (248 m 2 g À1 ) titanium-zirconium oxide nanofibre surface was functionalised via a phosphonic acid coupling reaction to give different functional groups for attracting metal ions (i.e., phosphonate and amine groups). The cadmium adsorption capacity of the phosphonate-functionalised nanofibres was up to 10 times higher than that of the non-modified or amine-functionalised nanofibres. In addition, the cadmium adsorption on the phosphonatefunctionalised nanofibres was less dependent on the pH of analyte solutions than the metal oxide nanofibres where the surface charge changed in varied pH environments. The size of the nanofibrous web can be easily scaled for making a large web convenient for handling and recovery after use, compared with high surface area heavy metal ion adsorbents that are nanometre or micrometre in size.

Voltammetric method for the quantification of cadmium using non-commercial electrodes and minimal instrumentation

“…This result demonstrates that it is possible to select any of the pH values to develop the voltammetric method. The stability of the limiting current matches the species distribution diagram for cadmium 24 , where Cd 2+ is stable until pH 8. However, several voltammetric determinations of cadmium are carried out at pH 5 8,25 ; that is the reason why this value was selected to develop the method.…”

Adsorbents Based on Electrospun Nanofibers

“…However, the heavy metal ions are in different states depending on solution pH, and the active component in nanofibers is unstable or dissolves under strong acidity, which would significantly influence the removal capacity, so the initial pH value of the solution should be optimized (Fig. 19.4c) [31,40,68]. Importantly, the initial concentration and the extraction time also have great impact on the adsorption capacity.…”

“…To increase the adsorption of heavy metals on nanofiber materials, the following methods have attracted the most attention: (1) utilizing polymers which contain a molecular functional group as resources to electrospinning, such as cellulose acetate (CA), silk fibroin (SF), wool keratin (WK), and PA-6 [15,[64][65][66][67]; (2) surface modification with functional group (the removal efficiency of heavy metal ions increases significantly after the adsorbents have been modified by functional group of -NH 2 , -SH, -SO 3 H, -COO , etc.) [35,62,68]; and (3) increasing the surface areas of nanofibers [31].…”

Electrospun fibrous membranes for efficient heavy metal removal

“…To deal with it, another inorganic component with good mechanical property can be introduced. A mesoporous TiO 2 /ZrO 2 nanofibrous membrane was prepared by electrospinning the mixture of titanium (IV) isopropoxide and zirconium (IV) propoxide in PVP, and subsequent thermal treatment to remove the organic components. Pluronic P123 was added in the electrospinning precursor to increase the surface area of nanofibers by generating intra‐fibrous mesopores.…”