Palak Bansal

Assessment of solar photocatalytic degradation and mineralization of amoxicillin trihydrate (AMT) using slurry and fixed-bed batch reactor: efficacy of parabolic trough collector

Heterogeneous photocatalytic mineralization of amoxicillin trihydrate (AMT) using TiO2 in suspended and supported form has been investigated in the present study. Cement beads and alginate balls were used for the immobilization of TiO2 for the degradation of AMT. The dip coating method was used for catalyst immobilization on the cement beads, whereas the catalyst was physically entrapped in alginate gel. 87%, 69% and 51% degradation was observed under shallow pond slurry reactor, coated cemented beads and immobilized sodium alginate balls, respectively, at optimized conditions. XRD and solid spectra analysis of TiO2 confirmed that no deformities occurred in the structure of catalyst after use. Reduction in COD and TOC along with the generation of ammonium ions further indicates the mineralization of AMT. Experiments conducted on a parabolic trough collector (PTC) with TiO2 immobilized cement beads at a flow rate of 1.0 L min−1 in the presence of oxidant (0.12 g L−1) yielded 92% degradation within 4 h of irradiation. The structure of TiO2 was found to be intact after the fifth recycle.

Catalyst-coated cement beads for the degradation and mineralization of fungicide carbendazim using laboratory and pilot-scale reactor: catalyst stability analysis

ABSTRACT The fixed-bed photocatalytic degradation of fungicide carbendazim using catalyst-coated spherical cement beads has been investigated. Thirty beads with optimum size 13 mm along with 0.3 gL−1 H2O2 with an initial concentration of carbendazim of 10 mgL−1 were the optimized conditions for better degradation. The reduction in COD and total organic carbon along with the generation of nitrite and nitrate ions under the optimized conditions confirms the complete mineralization of compound. The suggested degradation pathway for carbendazim has also been proposed as intermediates formed during photodegradation were analyzed through gas chromatography–mass spectrometry. The coated cement beads were found to be durable even after 30 cycles as confirmed by scanning electron microscopy and energy dispersive spectroscopy analysis. Scale-up trails have also been carried out in a solar-baffled fixed-bed reactor for the degradation of pollutant to seek the commercial viability of the technique. GRAPHICAL ABSTRACT

Stability and durability studies of TiO2 coated immobilized system for the degradation of imidacloprid

The present article demonstrates the use of supported TiO2 for studying the degradation of an insecticide, imidacloprid (IMI), along with durability studies of the catalyst. Operating conditions for the best degradation were optimized in suspension mode by varying the dose of TiO2, H2O2, pH and area/volume ratio of the batch reactor. With all conditions optimized, approximately 95% degradation of IMI was achieved after 3 h of photocatalytic treatment. For fixed-bed studies, TiO2 coated spherical cement beads were used for the degradation of IMI. Studies on the number of catalyst coatings, calcination temperature and catalyst durability were undertaken for the degradation. Spherical beads having a diameter of around 2.0 cm with two coatings of catalyst were efficient enough for 89% degradation of IMI after 6 h of treatment. The stability and efficacy of the supported catalyst were assessed by recycling the beads more than 30 times. The catalyst was characterized by SEM/EDS, XRD and DRS analysis. The durability of the catalyst was further confirmed by using catalyst coated beads that had previously been used for 100 cycles. The mineralization of IMI was validated by reduction in COD along with chloride ion (Cl−1) generation. A tentative degradation pathway for IMI has been proposed by carefully identifying the intermediates using GC-MS analysis.

N, Ag co-doped TiO2 mediated modified in-situ dual process (modified photocatalysis and photo-Fenton) in fixed-mode for the degradation of Cephalexin under solar irradiations

Novel FeNAgTiO2 composite beads possessing unusual characteristics of modified in-situ dual process (modified photocatalysis and photo-Fenton) resulted in reduction in treatment time of Cephalexin (CEX). These composite beads were prepared using NAgTiO2 and waste foundry sand (FS) and fly-ash (FA) as alternative source of iron. The modified TiO2 was characterized through SEM/EDS, DRS, XRD, TGA, FTIR, XPS and Raman spectroscopy to affirm the distribution of Ag and N on TiO2 surface. The modified in-situ dual process using FeNAgTiO2 composite beads yielded 77% degradation of CEX after 60 min of solar irradiations with overall synergy of 24% over individual processes. FeNAgTiO2 composite beads were characterized through SEM/EDS, XRD and DRS to confirm the presence of Fe along with Ag, N and TiO2 on the surface of beads. These composite beads were stable and active even after 15 recycles. The mineralization of CEX was validated through reduction in COD and TOC along with generation of anions while intermediates were identified through GC-MS analysis.