br Experimental details br Results and

Experimental details
Results and discussion
Photocatalytic activity of catalyst – degradation of RhB
Photocatalytic mechanism Based on the experimental results a possible mechanism was proposed for photocatalytic reactions of 0.75 wt% Ba2+ & 0.25 wt% Zr4+ co-doped TiO2 nanomaterial.
Conclusions The UV-DRS analysis shows that co-doping of Ba2+& Zr4+ into TiO2 shifts the absorbance band of TiO2 from UV to visible region and the band gap national prevalence  is reduced for all co-doped catalysts. All the catalysts are in nanometer range, which was strongly supported by the XRD and TEM analysis. The largest reduction gap and high photocatalytic activity was observed for co-doped catalysts of 0.75 wt% of Ba2+ & 0.25 wt. % of Zr4+. The optimum condition for the degradation of RhB by co-doped catalyst was found at catalyst weight of 100 mg, initial dye concentration 5 mgL−1 and solution pH is 8 respectively.
Acknowledgments
Introduction Many agricultural pesticides and chlorobiphenyls are found in the environment. The majority of pesticides gained popularity after the Second World War (Atoko et al., 2015; Chelme-Ayala et al., 2011; Kaushik and Kaushik, 2007), while chlorobiphenyls are a group of pollutant chemicals that were utilised in the manufacturing of electrical equipment and hydraulic systems (Hughes et al., 2015; Ishikawa et al., 2007), before stringent regulation and bans were imposed to both groups because of their acute toxicity, suspected endocrine, immuno- and neuro-toxicity, and bioaccumulation capabilities (Manickum and John, 2014; Marx-Stoelting et al., 2014; Selli et al., 2008). Many of these banned substances are still present in the environment and those under strict regulation are typically detected in higher concentrations than stipulated. South Africa still experiences a high number of persistent organic pollutants in the environment, though most of these substances have been banned for many years (Ryan et al., 2012). Conventional and traditional water and wastewater treatment facilities are not adequately effective at treating most complex structure organic chemical groups. The representative group of compounds in this study are 1.1.1-trichloro-2.2-bis(4-chlorophenyl)ethane (DDT), chlordane and 2.3.4-trichlorobiphenyl. One of the more effective technologies in dealing with emerging pollutants are advanced oxidation processes (AOPs), as they are generally non-selective and are capable of completely mineralising most organic chemical species (Ângelo et al., 2013; Demeestere et al., 2007; Carp et al., 2004). Advanced oxidation degradation of organic pollutants is achieved by generation of free hydroxyl (OH°) radicals using various technologies such as and a combination including ozonation, ultra-violet (UV) light, semiconductor photocatalysts, hydrogen peroxide, ultra-sound, and Fenton reagent (Levya-Diaz et al., 2015; Suzuki et al., 2015). Photocatalysis is one of the techniques that have found diverse applications in the treatment of persistent organic micro-pollutants. The nucleus of the photocatalytic concepts is embedded on the generation of energy bandgaps upon photon excitation of semiconductor materials. When light photons of a sufficient quantum and corresponding wavelength comes into contact with electrons on material surfaces such as semiconductors, the energy carried by the photons is absorbed, which results in the electrons moving to a higher energy state (conduction band). The absorbed energy can be relinquished by the electrons and dissipated in the form of photon energy, this result in electron descent to lower orbitals where they settle at characteristic ground energy states (valence band). This is referred to as electron hole pairs recombination, the recombination of the generated charges competes and minimises the trapping of free ionic chargers. The facilitation of effective photocatalytic degradation requires that the recombination of the electron and positive hole be prevented through reaction inhibitors in the form of electron donors and electron acceptors. Oxygen is the primary electron acceptor that is typically utilised for the purposes of trapping electrons in photocatalysis. The oxygen molecule reacts with free electrons and is converted to superoxide upon acceptance and trapping of the electrons. The remaining surface bound positive hole though radical formations facilitate oxidation pathways.