Photocatalytic Degradation of Malachite Green Dye from Aqueous Solution Using Environmentally Compatible Ag/ZnO Polymeric Nanofibers

Abstract

An efficient, environmentally compatible and highly porous, silver surface-modified photocatalytic zinc oxide/cellulose acetate/ polypyrrole ZnO/CA/Ppy hybrid nanofibers matrix was fabricated using an electrospinning technique. Electrospinning parameters such as solution flow rate, applied voltage and the distance between needles to collector were optimized. The optimum homogenous and uniform ZnO/CA/Ppy polymeric composite nanofiber was fabricated through the dispersion of 0.05% wt ZnO into the dissolved hybrid polymeric solution with an average nanofiber diameter ranged between 125 and 170 nm. The fabricated ZnO-polymeric nanofiber was further surface-immobilized with silver nanoparticles to enhance its photocatalytic activity through the reduction of the nanofiber bandgap. A comparative study between ZnO polymeric nanofiber before and after silver immobilization was investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and thermal gravimetric analysis (TGA). The photocatalytic degradation efficiency of the two different prepared nanofibers before and after nanosilver immobilization for malachite green (MG) dye was compared against various experimental parameters. The optimum degradation efficiency of nanosilver surface-modified ZnO-polymeric nanofibers was recorded as 93.5% for malachite green dye after 1 h compared with 63% for ZnO-polymeric nanofibers.

Keywords: ZnO/CA/Ppy; composite nanofiber; malachite green; photocatalytic; silver immobilization; wastewater remediation.

Figure 1

SEM micrographs of electrospinning processing parameters on fabricated ZnO polymeric composite nanofiber: (A) Cellulose acetate concentration (8–16 wt%), (B) solution flow rate (0.2–1 mL/h), (C) applied voltage (10–30 KV), (D) distance between needle tip and collector (8–18 cm) and (E) amount of loaded ZnO NPs as a filler (0.02–0.1 wt%).

Figure 1

SEM micrographs of electrospinning processing parameters on fabricated ZnO polymeric composite nanofiber: (A) Cellulose acetate concentration (8–16 wt%), (B) solution flow rate (0.2–1 mL/h), (C) applied voltage (10–30 KV), (D) distance between needle tip and collector (8–18 cm) and (E) amount of loaded ZnO NPs as a filler (0.02–0.1 wt%).

Figure 2

TEM micrographs of ZnO polymeric composite nanofiber (A) before silver immobilization and (B) after silver immobilization.

Figure 3

XRD patterns of various prepared matrices, (A) ZnO NPs, (B) Ppy NPs, (C) ZnO polymeric composite nanofibers and (D) ZnO polymeric composite nanofibers after silver immobilization.

Figure 4

FTIR spectrophotometric analysis for ZnO polymeric composite nanofiber (A) before silver immobilization and (B) after silver immobilization.

Figure 5

TGA profiles of ZnO polymeric nanofiber (A) before silver immobilization and (B) after silver immobilization.

Figure 6

Effect of contact time on MG dye photocatalytic degradation process using ZnO polymeric nanofiber after and before silver immobilization (initial dye concentration = 20 ppm, nanofiber dose = 0.1 g, pH = 7 at room temperature).

Figure 7

Effect of initial MG dye concentration on MG dye photocatalytic degradation process using ZnO polymeric nanofiber after and before silver immobilization (contact time = 60 min, nanofiber dose = 0.1 g, pH = 7 at room temperature).

Figure 8

Effect of adsorbent dosage on the MG dye photocatalytic degradation process using ZnO polymeric nanofibers after and before silver immobilization (initial dye concentration = 20 ppm, pH = 7, contact time = 60 min at room temperature).

Figure 9

Effect of dye solution pH on the MG dye photocatalytic degradation process using ZnO polymeric nanofibers after and before silver immobilization (initial dye concentration = 20 ppm, nanofiberdose = 0.1 g, contact time = 60 min at room temperature).

Figure 10

Effect of dye solution temperature on the MG dye photocatalytic degradation process using ZnO polymeric nanofibers after and before silver immobilization (initial dye concentration = 20 ppm, nanofiberdose = 0.1 g, contact time = 60 min at pH = 7).

Figure 11

Reusability of ZnO polymeric composite nanofibers before and after silver immobilization as photocatalytic materials for MG dye decolorization process.

Figure 12

OH⁺ Malachite green dye → products (CO₂ and H₂O). Scheme diagram of the photocatalytic degradation mechanism of malachite green dye (MG) on ZnO polymeric nanofiber immobilized with silver.