Natural Solar Radiation Research Articles

Concentrating technologies with reactor integration and effect of process variables on solar assisted pyrolysis: A critical review

Solar pyrolysis shows promise as a technique to generate solar fuels in the context of the future economy besides mitigating emissions. The prior experiments were mainly demonstrated in an indoor environment using a solar simulator while recent studies have been established using natural solar radiation. An integrated solar receiver-reactor is likely to be employed to generate high-temperature for the conversion of feedstocks into valuable products. Undoubtedly, parabolic trough and parabolic dish with the integration of fixed bed batch reactor are the two-common type of concentrators that has been widely used by the researcher. The effectiveness of a solar pyrolysis process depends not only on the reactor configuration but also on the process variables. Temperature is the most crucial factor that dominant product yields. The current literature is scattered, vague, and difficult to understand the configuration of the system and operating parameters that affect the yield of solar products. In order to carry out an efficient solar pyrolysis reaction, the latest design and fabrication of different modes of experimental setup is presented. Moreover, operating factors that dominate the product quantity are elaborately discussed. A critical discussion, some challenges, and its probable solutions during scale-up of a pyrolysis system are also delivered.

Graphene-Based TiO2 Nanocomposite for Photocatalytic Degradation of Dyes in Aqueous Solution under Solar-Like Radiation

This study presents a novel method for the development of TiO2/reduced graphene oxide (rGO) nanocomposites for photocatalytic degradation of dyes in an aqueous solution. The synergistic integration of rGO and TiO2, through the formation of Ti–O–C bonds, offers an interesting opportunity to design photocatalyst nanocomposite materials with the maximum absorption shift to the visible region of the spectra, where photodegradation can be activated not only with UV but also with the visible part of natural solar irradiation. TiO2@rGO nanocomposites with different content of rGO have been self-assembled by the hydrothermal method followed by calcination treatment. The morphological and structural analysis of the synthesized photocatalysts was performed by FTIR, XRD, XPS, UV-Vis DRS, SEM/EDX, and Raman spectroscopy. The effectiveness of the synthesized nanocomposites as photocatalysts was examined through the photodegradation of methylene blue (MB) and rhodamine B (RhB) dye under artificial solar-like radiation. The influence of rGO concentration (5 and 15 wt.%) on TiO2 performance for photodegradation of the different dyes was monitored by UV-Vis spectroscopy. The obtained results showed that the synthesized TiO2@rGO nanocomposites significantly increased the decomposition of RhB and MB compared to the synthesized TiO2 photocatalyst. Furthermore, TiO2@rGO nanocomposite with high contents of rGO (15 wt.%) presented an improved performance in photodegradation of MB (98.1%) and RhB (99.8%) after 120 min of exposition to solar-like radiation. These results could be mainly attributed to the decrease of the bandgap of synthesized TiO2@rGO nanocomposites with the increased contents of rGO. Energy gap (Eg) values of nanocomposites are 2.71 eV and 3.03 eV, when pure TiO2 particles have 3.15 eV. These results show the potential of graphene-based TiO2 nanocomposite to be explored as a highly efficient solar light-driven photocatalyst for water purification.

Efficient solar removal of acetaminophen contaminant from water using flexible graphene composites functionalized with Ni@TiO2:W nanoparticles

This work presents the morphological, structural and photocatalytic properties of flexible graphene composites decorated with Ni@TiO2:W nanoparticles (TiNiW NPs) with an average size of 27 ± 2 nm. The TiNiW NPs were immobilized on the surface of a flexible graphene composite using a PVA-based slurry-paste (FG/TiNiW composite). The SEM study showed that the TiNiW NPs remained exposed on the surface of the FG/TiNiW composite, which benefited its photocatalytic activity. The photocatalytic performance for the degradation of acetaminophen (ACT) was evaluated using both the TiNiW powders and the FG/TiNiW composite, obtaining maximum degradation efficiencies of 100 and 86%, respectively, after 3 h under natural solar irradiation. The degradation of ACT was caused mainly by the reactive oxygen species such as OH radicals and h+, which was confirmed by scavenger experiments. Photoluminescence, XPS and absorbance experiments revealed that oxygen vacancy defects were created by i) doping the TiNiW NPs with W and by ii) introducing graphene into the composites. These defects enhanced the absorbance of light in the range of 400–800 nm, which in turn, promoted the photocatalytic degradation of ACT. Moreover, the reuse experiments confirmed that both the TiNiW NPs and FG/TiNiW composite were very stable for the degradation of ACT, since degradation efficiencies >82% were obtained after 4 reuse cycles for both photocatalysts. The experimental findings of this work demonstrate that the flexible TiO2/graphene composites are a feasible option for the removal of pharmaceutical contaminants from water using natural solar irradiation.

Direct oxidation of peroxymonosulfate under natural solar radiation: Accelerating the simultaneous removal of organic contaminants and pathogens from water

This study investigates the effectiveness of non-activated peroxymonosulfate (PMS) as oxidative agent for water purification in the presence and absence of natural solar radiation. The inactivation of three pathogens (Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa) and degradation of three Contaminants of Emerging Concern (CECs) (Trimethoprim-TMP, Sulfamethoxazole-SMX and Diclofenac-DCF) was simultaneously assessed in isotonic water (IW) by testing a wide range of PMS concentrations (from 0.0001 to 0.01 mM). A significant oxidative effect of PMS in darkness was obtained for both bacteria and CEC abatement, but when irradiated with solar light, results demonstrated a great enhancement on all bacterial kinetic rates, reaching >5 Log reduction in 30 min (1.5 kJL−1 of QUV) with 0.005 mM of oxidant as the best concentration. For CECs, higher degradation performance was obtained with 0.01 mM, 80% removal of DCF, SMX and TMP was achieved in 16 min (1.5 kJL−1), 27 min (9.4 kJL−1) and 150 min (16.8 kJL−1), respectively. Besides, the influence of inorganic species on the global PMS/solar system performance was assessed by testing its effectiveness in distilled water (DW), natural well water (WeW) and diluted well water (d-WeW) at 0.01 mM. Results revealed that (i) high chloride concentration (IW) has an important positive effect, (ii) the presence of a complex inorganic chemical water composition reduced the system efficiency (WeW), and (iii) no differences were obtained from the presence of low or high contents of carbonates/bicarbonates (WeW versus d-WeW), obtaining the following global PMS/solar efficiency performance order: IW > DW > WeW = d-WeW.

Controlled synthesis of photoactive gallium based sillenite single crystal and its application in environmental remediation

Among the numerous photocatalytic materials studied for potential application in degradation of organic effluents and antibiotic wastes, sillenite materials emerge as important candidates. In the present work, Ga based sillenite has been used to degrade aqueous persistent organic pollutants such as bisphenol (BPA) and Norfloxacin (NF) in presence of natural solar irradiation. Sillenite based oxides have exhibited various physico chemical applications due to their photocatalytic nature. Here, gallium based sillenite, Bi24Ga2O39, has been successfully synthesized through two different techniques, hydrothermal route (HY) and solid state reaction (SS) method. X-Ray Diffraction patterns and Rietveld refinement of same revealed the occurrence of sillenite single phase. Morphological investigation by Scanning Electron Microscopy revealed regular tetrahedral morphology of HY sample. X-ray photoelectron and Raman spectroscopy were performed to analyze the chemical composition and its environment. UV–Visible spectroscopy on sillenites was used to analyze and calculate the effective optical band gap energy ~2.55 eV (HY) and ~2.76 eV (SS) respectively. Photoelectrochemical measurements performed on the samples showed appreciable photocurrent response (~1.9 μA/cm2 for HY sample). The photoactivity of samples have been utilized for degradation of aqueous persistent organic pollutants, such as methylene blue, norfloxacin and bisphenol A in presence of visible light degrading upto 92%, 82% and 84% (HY) respectively.

Marriage of 2D Covalent-Organic Framework and 3D Network as Stable Solar-Thermal Still for Efficient Solar Steam Generation.

In this work, a diketopyrrolopyrrole-based 2D covalent-organic framework (COF) is realized and featured with broadband optical absorption and high solar-thermal conversion performance. Moreover, a 3D hierarchical structure, referred to as COF-based hierarchical structure (COFHS), is rationally designed to achieve an enhanced photothermal conversion efficiency. In this water evaporator, diketopyrrolopyrrole is immobilized into conjugated COF to achieve enhanced light absorption, whereas a porous PVA network scaffold is utilized to support COF sheets as well as to enhance the hydrophilicity of the evaporator. Due to this structural advantage, COFHS displays a high solar-to-vapor energy conversion efficiency of 93.2%. Under 1 sun AM1.5 G irradiation, a stable water evaporation rate of 2.5kg m-2 h-1 can be achieved. As a proof-of-concept application, a water collection device prepared with the COFHS can achieve high solar-thermal water collection efficiency of 10.2L m-2 d-1 under natural solar irradiation. The good solar-thermal conversion properties and high-water evaporation rate make the COFHS a promising platform for solar-thermal water production.

Photocatalytic degradation of environmental pollutant using nickel and cerium ions substituted Co0.6Zn0.4Fe2O4 nanoferrites

In the present investigation, toxic environmental pollutant, i.e., Congo red dye photocatalytic degradation was achieved using Co0.6Zn0.4−xNixCeyFe2−xO4 (x = 0.0, 0.1, 0.2, 0.3; y = 0.0, 0.05, 0.10, 0.15) ferrite-based nanomaterials. The nanoferrites were synthesized with the usage of sol–gel auto-combustion fabrication technique. Their microstructural, optical and magnetic, properties were analysed, using various characterization techniques. The observed XRD (X-ray diffraction) diffraction patterns indicate the existence of single-phase spinel cubic structure along with Fd3m space group symmetry and, the crystallite size calculated using Scherrer formula was found in the dimensions of 38–49 nm. The formation of agglomerated, dense, and spherical magnetic nanoparticles with an average grain size of 51 nm and 62 nm for the undoped specimen (x = 0.0, y = 0.0) and doped specimen (x = 0.2, y = 0.10) were observed from the FESEM (Field emitting scanning electron microscopy) micrographs analysis. From the M–H curves data, it was concluded that the maximum value of Ms (70.17 emu/g) and Hc (266.43 Oe) was attained by the Co0.6Zn0.1Ni0.3Ce0.15Fe1.85O4 nanoferrite. The present investigation concentrates on the photocatalytic degradation of Congo red dye under the natural solar irradiation in which we improved the photocatalytic efficiency upto 94.6% after 60 min of irradiation with the utilization of substituted Co0.6Zn0.1Ni0.3Ce0.15Fe1.85O4 nano photocatalyst. Thus, synthesized Co–Zn nanoferrites can be utilized for potential applications in wastewater treatment.

Toxicity reduction of persistent pollutants through the photo-fenton process and radiation/H2O2 using different sources of radiation and neutral pH

The presence of toxic compounds in aquatic bodies is of great concern, and the Fenton, photo-Fenton and radiation/H2O2 processes can be applied in the remediation of these compounds due to their efficiency and advantages. However, these processes need to be investigated to make them more viable and environmentally friendly. Thus, the reduction of toxicity was evaluated, through ecotoxicological tests with Artemia salina and Lactuca sativa, of the compounds 2,4-D, diazepam, nicotine and paracetamol (acetaminophen) by the Fenton, photo-Fenton and radiation/H2O2 process with UVC, UVA and natural solar radiation at neutral pH with low concentrations of Fe2+ and H2O2. The UVC/H2O2 process was efficient in the degradation of nicotine (74%), the photo-Fenton process was more efficient in the degradation of 2,4-D (82%), diazepam (27%) and paracetamol (85%) using solar radiation, UVA and UVC respectively. The toxicity and total organic carbon (TOC) tests showed a reduction in the toxicity of the compounds after treatment, except for diazepam, which was more resistant to the process, leading to a higher mortality of Artemia salinas (92%) and less relative seed germination of Lactuca sativa (40%).

Improving photocatalytic efficiency of MnFe2O4 ferrites via doping with Zn2+/La3+ ions: photocatalytic dye degradation for water remediation.

The interference of industrial effluents such as dyes, surfactants, metals, polycyclic aromatic hydrocarbons, and pharmaceutical waste has become a severe global problem for human health due to their carcinogenic, mutagenic, and toxic properties. Ferrites were considered promising photocatalysts for the degradation of organic and inorganic dyes. This study mainly focused on improving the photocatalytic performance of MnFe2O4 nanoferrites via doping of Zn2+ and La3+ ions. The zinc and lanthanum substituted Mn1-xZnxLayFe2-yO4 nanoferrites were prepared by the sol-gel auto-combustion technique for the degradation of organic textile malachite green dye (MGD) under the natural solar irradiation. The synthesized nanoferrites were investigated for their structural properties, surface morphology and elemental analysis, optical studies, magnetic properties, and photocatalytic performance by XRD, FESEM/EDX, FTIR/Raman spectrum, vibrating sample magnetometer, and UV-visible spectrophotometer, respectively. The substitution of zinc and lanthanum improved the photocatalytic efficiency of nanoferrites, and about 96% of MGD was degraded by Mn0.97Zn0.03La0.04Fe1.96O4 after 60 min of irradiation. The results showed the pseudo-first-order kinetics for dye degradation using undoped and Zn/La-doped MnFe2O4 photocatalysts.

Impact of phthalocyanine structure as photosensitizer for ZnO nanophotocatalyst under natural solar irradiation

Novel composites of zinc oxide (ZnO) and copper phthalocyanines (CuTriPc and CuPc) were synthesized as efficient natural solar light photocatalysts for the photodegradation of organic wastewater pollutants. Spectroscopic and analytical measurements confirmed that both bulky triazolo copper phthalocyanine (CuTriPc) and unsubstituted planer (CuPc) were successfully coupled with ZnO nanoparticles. The synthesized nanocomposites were investigated as natural solar radiation photocatalysts toward the photodegradation of methylene blue (MB) analogue dye. The prepared CuTriPc/ZnO nanocomposite was proven to be an efficient solar light photocatalyst compared to pure ZnO and the unsubstituted CuPc/ZnO.

UV-induced citrus resistance to spider mites (Tetranychus urticae)

Under reduced solar UV radiation, such as in polycarbonate-covered nurseries, the two-spotted spider mite Tetranychus urticae is a major pest of all citrus cultivars, while under natural solar radiation, only sensitive cultivars are infested. We hypothesized that citrus resistance to T. urticae is induced by UV. We infested seedlings of Citrus volkameriana rootstock with T. urticae under natural and under UV-screened solar radiation, along with non-infested control seedlings. We then monitored the establishment of the spider mites and analyzed the volatile leaf profile using GC-MS. The density of spider mites was reduced dramatically on seedlings exposed to solar UV. Overall, ninety volatile compounds (47 monoterpenes, 35 sesquiterpenes, and 8 aldehydes) were detected in the leaves, many of them known to be herbivore-induced and/or UV enhanced. Their levels were affected not only by solar UV radiation or by mite infestation independently. Synergistic interaction of these two factors resulted in 90% of the volatiles suppressed by T. urticae infestation in the absence of UV radiation. This suggests that plant induced resistance is dependent on exposure to UV radiation.

Cell wall response to UV radiation in needles of Picea omorika

The UV-B represents the minor fraction of the solar spectrum, while UV-C is not contained in natural solar radiation, but both radiation types can cause damaging effects in plants. Cell walls (CWs) are one of the targets for external stressors. Juvenile P. omorika trees were treated either with 21 day-high doses UV-B or with 7 day- UV-C in open-top chambers. Using spectroscopic and biochemical techniques, it was shown that the response to UV radiation includes numerous modifications in needle CW structure: relative content of xylan, xyloglucan, lignin and cellulose decreased; cellulose crystallinity changed; yield of lignin monomers with stronger connection of CC in side chain with the ring increased; re-distribution of inter- and intra-polymer H-bonds occurred. The recovery was mediated by an increase in the activities and changes in isoform profiles of CW bound covalent peroxidases (POD) and polyphenol oxidases (PO) (UV–B), and ionic POD and covalent PO (UV–C). A connection between activities of specific POD/PO isoforms and phenolic species (m- and p-coumaric acid, pinoresinol and cinnamic acid derivatives) was demonstrated, and supported by changes in the sRNA profile. In vivo fluorometry showed phenolics accumulation in needle epidermal CWs. These results imply transversal connections between polymers and changed mechanical properties of needle CW as a response to UV. The CW alterations enabled maintenance of physiological functions, as indicated by the preserved chlorophyll content and/or organization. The current study provides evidence that in conifers, needle CW response to both UV-B and UV-C includes biochemical modifications and structural remodeling.

Photodecomposition of natural organic metal-binding ligands from deep seawater

To reveal the effect of solar irradiation on the biogeochemical cycling of trace metals in the open ocean, the photodecomposition of organic iron- and copper-binding ligands was examined in an experiment using filtered seawater collected from a deep layer of the East China Sea. Six days of natural solar irradiation caused a significant decrease in the concentrations of both ligands, along with the loss of fluorescent dissolved organic matters. The relative decrease of iron-binding ligands, which are considered to be mainly composed of humic substances, was larger than that of copper-binding ligands or humic-like fluorescence. This may be attributable to relatively high photoreactivity of hydrophilic fluvic acids, which have higher affinity to ferric ions. Surprisingly, an accumulation of both iron- and copper-binding ligands was observed in the dark control bottles, but without a significant change in the fluorescence of humic-like substances. In conclusion, the upwelling of deep seawater into the sunlit surface layer can result in the rapid loss of the complexation capacity for both iron and copper ions. The stronger ligands for both metals, which were readily decomposed by sunlight irradiation, appears to have a similar composition, suggesting that competition could be important to determine the solubility and bioavailability of iron and copper.

Role of H+, HF, SO42− and kaolin in fixing Hg of coal fire sponge

Coal fire sponges (CFS) are common in coal-fire areas. Due to the enrichment of Hg in CFS, large amounts of Hg are released by CFS into the atmosphere via natural weathering or solar radiation. Therefore, CFS should be of concern in Hg pollution management and control globally. In addition, CFS changes the Hg cycle path by capturing Hg from coal fires that would have entered the atmosphere. In this study, the concentration, distribution, species, and enrichment mechanism of CFS Hg were investigated. The results showed that the Hg concentration in CFS ranged from 1008 to 35,310 ng/g, with an average of 8932 ng/g (CFS number, n = 153). The Hg concentration of CFS in different types of land was found to be significantly inhomogeneous. To determine the status of subterranean spontaneous combustion, the Hg concentration was added, which can improve the effect of coal-fire monitoring. Compared to the background area topsoil, CFS was enriched in Hg, acid, SO42−, and total fluoride. The Hg species in CFS was primarily HgSO4, followed by HgO. However, the primary Hg species in the surrounding topsoil were HgCl2 and HgO. By the simulation experiment, it was determined that hydrofluoric acid (HF) was beneficial to activate the stable species in the coal-fire areas. HgCl2, HgO, or Hg0 were ionized by acid liquor or HF, which can promote Hg migration and increase the adsorbed ratio; in the presence of SO42−, the primary Hg species was HgSO4. Ultimately, Hg was absorbed by clay minerals and organic matter. The high-efficiency activation of steady Hg species by the coal-fire HF should be studied further.

Mathematical models of sunlight for dynamic lighting systems of agricultural objects

A promising method for illuminating agricultural objects is dynamic lighting with a change in the luminous flux and correlated color temperature of artificial optical radiation sources adapted to the natural dynamics of sunlight. The purpose of this study is to develop mathematical models of changes in illumination on the control surface and correlated color temperature of natural solar radiation during the day. The experimental method established a linear relationship between the correlated color temperature of sunlight and the surface illumination in the direction of the Sun. The regularity of time changes in the height of the Sun above the horizon was determined. The functional dependence of illumination on the height of the Sun above the horizon was revealed. The equations can be used to control artificial light sources in the systems of dynamic illumination of agricultural objects in order to increase the productivity of animals.

Solar-driven hydrogen production from a water-splitting cycle based on carbon-TiO2 nano-tubes

This study illustrates the structuring of the TiO2 within carbon nano-tubes to enhance the solar-driven production of hydrogen (S-DPOH) via water splitting. The newly developed Carbon-TiO2 nano-tubes (C-Ti-NTs) aimed at improving the practical applications of TiO2 composites under natural solar irradiation conditions, enhancing the absorption of UV and VIS-light, reduces the required bandgap energy and decreases the chance for photo-induced-charges recombination. The C-Ti-NTs were prepared using an alkaline hydrothermal method, characterized using different state of art techniques and tested for the S-DPOH via water splitting. Adding a carbon layer on the surface of TiO2 nano-tube with a thickness of ~1 nm reduced the bandgap of the C-Ti-NTs ≤ 0.88 eV, improved the quantum efficiency under UV light to 100%, enhanced the absorption capacity under VIS-light and extremely suppressed the charge recombination. The S-DPOH achieved a cumulative production of hydrogen (CPOH) during 50 h of solar irradiation of 43.75 mmol at a rate RPOH′of H2 production of 38.66 ± 0.655 mmol/h.g, which is 1.5 folds higher than the maxim rate reported for pure TiO2-based photocatalyst. The obtained results confirmed the contribution of TiO2 for the production of hydrogen, which is expected to open a new insight towards the importance of architectural design and band engineering in the practical development of sustainable solar energy harvesting applications.

Tailoring Broad-Band-Absorbed Thermoplasmonic 1D Nanochains for Smart Windows with Adaptive Solar Modulation.

Controlling solar transmission through windows promises to reduce building energy consumption. A new smart window for adaptive solar modulation is presented in this work proposing the combination of the photothermal one-dimensional (1D) Au nanochains and thermochromic hydrogel. In this adaptive solar modulation system, the Au nanochains act as photoresponsive nanoheaters to stimulate the optical switching of the thermochromic hydrogel. By carefully adjusting the electrostatic interactions between nanoparticles, different chain morphologies and plateau-like broad-band absorption in the NIR region are achieved. Such broad-band-absorbed 1D nanochains possess excellent thermoplasmonic effect and enable the solar modulation with compelling features of improved NIR light shielding, high initial visible transmittance, and fast response speed. The designed smart window based on 1D Au nanochains is capable of shielding 94.1% of the solar irradiation from 300 to 2500 nm and permitting 71.2% of visible light before the optical switching for indoor visual comfort. In addition, outdoor cooling tests in model house under continuous natural solar irradiation reveal the remarkable passive cooling performance up to ∼7.8 °C for the smart window based on 1D Au nanochains, showing its potential in the practical application of building energy saving.

Colloidal CdS sensitized nano-ZnO/chitosan hydrogel with fast and efficient photocatalytic removal of congo red under solar light irradiation

Colloidal CdS sensitized nano-ZnO/chitosan (CdS@n-ZnO/CS) hydrogel was prepared and characterized extensively by XRD, SEM-EDS, TEM, UV–Vis DRS, FT-IR and TGA. The photocatalytic activity of CdS@n-ZnO/CS was evaluated with the photodegradation of congo red (CR) as an organic pollutant under solar light irradiation. The influences of initial dye concentration, catalyst dosage, recycling runs, and radical scavenger on decolorization of CR by CdS@n-ZnO/CS were investigated. 95% of CR was removed in just 1 min for 5.0 mg L−1 and 94.34% of CR was removed in 30 min for 100 mg L−1. CdS@n-ZnO/CS exhibited an excellent and ultra-fast performance toward CR removal under solar light due to the synergistic effect of adsorption by chitosan and photocatalysis by ZnO and CdS in CdS@n-ZnO/CS hydrogel. Radical trapping control experiments indicated that h+ and O2− played the major role for CR decolorization. The high performance of CdS@n-ZnO/CS hydrogel was also demonstrated under natural solar light irradiation, suggesting that CdS@n-ZnO/CS hydrogel could be used in practical wastewater treatment.

Photo-Fenton process under sunlight irradiation for textile wastewater degradation: monitoring of residual hydrogen peroxide by spectrophotometric method and modeling artificial neural network models to predict treatment

In this work, a procedure was elaborated to quantify hydrogen peroxide (H2O2) after degradation tests of dyes present in a synthetic textile matrix. For this purpose, based on the intensity of radiation absorption of the peroxovanadium cation, which was formed by the reaction between the oxidant and vanadate ions, ultraviolet/visible spectrophotometry technique was used. The most suitable experimental condition was composed of concentrations of 0.05 mol L−1 (NH4VO3) and 0.3 mol L−1 (H2SO4). The system for dye treatment involved the photo-Fenton process under simulated sunlight. In this case, concentrations of 900 mg L−1 (H2O2) and 4 mg L−1 (iron) in pH 3 were the most efficient for degrading contaminants. An efficiency of 94.49% was obtained after 180 min of reaction, the time in which the presence of the oxidant was no longer verified. The kinetic monitoring showed a two-stage degradation, described with accuracy greater than 96% by the linear and non-linear kinetic models of pseudo-first order. Additionally, the degradation under natural solar radiation was also studied, which resulted in an efficiency of 92.45% after 360 min and in the presence of the residual oxidant. Finally, via mathematical modeling and employing a Multilayer Perceptron neural network, with a 3-10-2 topology and BFGS 387 training algorithm, it was possible to predict the degradation and H2O2 residual concentration with an accuracy greater than 98%. Therefore, the degradation study developed and the proposed methodology for determining residual H2O2 proved to be adequate and capable of contributing positively to related research.

Natural and Simulated Solar Radiation.

The extra-terrestrial solar spectrum corresponds approximately to a black body of temperature about 5,800 K, with the ultraviolet region accounting for almost 8% of the total solar energy. Terrestrial solar spectral irradiance peaks at around 500 nm in the blue-green region, whereas the diffuse component peaks in the UVAI-blue region of the spectrum, with the infrared component comprising almost entirely direct radiation. Several factors impact on the magnitude and spectral profile of terrestrial solar spectral irradiance, and these include solar elevation, reflection from land and sea, air pollution, altitude above sea level and cloud cover. Measurements of erythemal UV from a number of ground-based networks around the world indicate an approximate 4-fold difference in ambient annual exposure between Australia and countries in northern Europe. In the absence of measured data, models to compute solar UV irradiance are a useful tool for studying the impact of variables on the UV climate. Simulated sources of sunlight based on a xenon arc lamp can be configured to give a close match to the spectral output of natural sunlight at wavelengths less than about 350 nm, and these are invaluable in the laboratory determination of sunscreen performance, notably the Sun Protection Factor (SPF). However, the divergence -between natural and simulated solar spectra at longer wavelengths may explain why SPFs measured in natural sunlight are less than those determined in the laboratory.