Industrial sludge remediation with photonic treatment using Ti-Ag nano-composite thin films: Persistent organic pollutant removal from sludge matrix

Abstract

Mechanically dewatered industrial sludge (MDIS) was treated using pure and silver-doped thin films (TFs) grown on quartz substrates. TFs were prepared using a sol-gel dip coating technique. The resulting films were annealed at 450 degrees C for 3 h and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Mixtures that were homogeneous in the UV A (380 nm) and UVvis (450 nm) regions of the electromagnetic spectrum were used as the irradiation source. The results revealed that illumination with different wavelengths helps to generate well-separated e(-)/h(+) pairs, resulting in a decrease in the recombination rate. An electron transfer chain model was also developed using the experimental results. The performance of the applied method was evaluated by observing variations in the sludge bound water content (SBWC), volatile solids removal rate (VSR), and the consumed and generated energy fluxes through endergonic and exergonic reactions. After treatment, SBWC was reduced from 65% +/- 1% to 39% +/- 1 and the highest VSR was measured to be 27 +/- 0.1 mg VSS cm(-2) h(-1). The consumed and recovered energy fluxes were 960 +/- 151 and 412 +/- 26 J g(-1) VSremoved, respectively. Raw sludge and polychlorinated biphenyls (Sigma 15PCB) and polyaromatic hydrocarbon (Sigma(16)PAH) concentrations were 4356.82 +/- 22 mu g kg(-1) and 446.25 +/- 4.8 mu g kg(-1), respectively. The Sigma(15) PCB and E-16 PAH concentrations in the treated sludge samples were 129.86 +/- 22 mu g kg(-1) and 34.85 +/- 13 mu g kg(-1), respectively. (C) 2014 Elsevier Ltd. All rights reserved.