Natural Solar Radiation Research Articles

Ag@Bi5O7I nanoparticles deposited on Bi(OH)3 nanosheets for boosting photocatalytic antibacterial activity under visible light irradiation

A novel Ag@Bi5O7I/Bi(OH)3 (AB) heterojunction was prepared and the enhanced photocatalytic antibacterial activity against Escherichia coli (E. coli) under visible light excitation was exhibited. 3 %AB (containing 3 wt% of Ag) presented best photocatalytic performance, and all of E. coli cells were inactivated within 5 min under natural solar light irradiation. The photocatalytic antibacterial mechanism of AB heterojunction was corroborated by SEM, live/dead cell staining and SDS-PAGE assay. The destruction of the cell membrane, the leakage of the intracellular protein and the decomposition of the protein were considered as the events occurred in the antibacterial process. The radical capture experiment confirmed that •O2– and e– played the dominant role in the destruction of the cell membrane and the decomposition of the protein. The improvement of the photocatalytic activity can be mainly ascribe to the construction of heterojunction, SPR effect resulted from Ag deposition, enhanced visible light absorption and more surface oxygen vacancies. These factors are advantageous to the generation of the photogenerated electrons and holes, and improve the spatial separation efficiency of the photogenerated charge. This study presented a promising Ag@Bi5O7I/Bi(OH)3 heterojunction as the photocatalyst for the potential application in the treatment of the bacterial contamination.

Experimental Determination of Mercury Photoreduction Rates in Cloudwater

AbstractRedox chemistry controls the behavior of mercury during long‐range atmospheric transport. Despite major progress in understanding the oxidation process in the atmosphere, the mechanism of mercury reduction, especially the aqueous‐phase and multi‐phase reactions in cloudwater, remains poorly known. Here we report experimentally determined rates of in‐cloud mercury photoreduction using cloudwater samples collected from a forested area in the Canary Islands, Spain. Mercury concentrations in cloudwater varied greatly from 0.04 to 19.9 nM (7.89 ± 6.11 nM) for total mercury and 0.02 to 4.98 nM (1.16 ± 1.49 nM) for the dissolved fraction, with particulate mercury being the dominant fraction in most of the samples. The mercury concentrations were elevated in comparison with those previously reported for atmospheric waters, reflecting the impact of a large‐scale forest wildfire that occurred shortly before the sampling campaign on a neighboring island. Mercury photoreduction was determined by two independent methods: under natural solar radiation at a nearby mountain site located in the free troposphere and under UV radiation in the laboratory. In addition to aqueous‐phase photoreduction, multi‐phase photoreduction involving particulate mercury also occurred in cloudwater, with the latter becoming dominant once dissolved mercury had been depleted. Overall, the pseudo‐first‐order rate constants for in‐cloud mercury photoreduction varied from 0.07 to 0.21 hr−1, which are one order of magnitude lower than the values presumed in global mercury transport models. Our results suggest that in‐cloud reactions alone are insufficient to account for mercury reduction in the atmosphere and that other pathways, such as gas‐phase reactions, must exist and need to be properly incorporated into future models.

Natural Solar Irradiation Produces Fluorescent and Biodegradable Nanoplastics.

Nanoplastics (NPs) have raised global concern owing to their potential health effects. Herein, after simulated and natural solar irradiation, polyethylene, polypropylene, polystyrene, and poly(vinyl chloride) nanoplastics (PVC NPs) were observed to exhibit enhanced fluorescence, particularly PVC NPs. Furthermore, the role of photoaged NPs as a potential fluorescence indicator was evaluated by exposing a model aquatic organism Daphnia magna to these NPs. Our results revealed that photoaged NPs exhibited strong fluorescence owing to the generation of conjugated π bonds, which can achieve π-π* electron transition with low energy consumption. Photogenerated fluorescence also enabled the photoaged NPs to act as efficient fluorescent tracers, which can help track NP migration in various organisms. The results of two-photon laser confocal scanning microscopy revealed that the photoaged NPs could translocate across biological barriers and accumulate in extraintestinal tissues in addition to being ingested and excreted. Moreover, compared with pristine NPs, the photoaged NPs underwent biodegradation more easily, probably because of increased hydrophilicity due to photogenerated oxygen-containing moieties. Therefore, in addition to producing fluorescent NPs without the attachment of external fluorescent dyes, the natural photoaging process can promote the migration and degradation of photoaged NPs in food chains.

Peroxymonosulfate/Solar process for urban wastewater purification at a pilot plant scale: A techno-economic assessment

The safe reuse of reclaimed water for agricultural irrigation has been considered as an alternative, feasible and sustainable option to address water scarcity. This work aims to validate the capability of the solar water photochemical process based on the synergistic effect between peroxymonosulfate (PMS) and natural solar radiation for actual urban wastewater (UWW) purification at a pilot plant scale using a solar Compound Parabolic Collector photo-reactor. The PMS/Solar process performance was assessed by monitoring simultaneously the inactivation of naturally occurring bacteria (Escherichia coli, Total coliforms, Enterococcus spp. and Pseudomonas spp.) as a potential tertiary treatment to fit the minimum bacterial requirements for UWW purification but also additional challenges have been in deep analysed simultaneously. In this regard, a global analysis including the degradation of three Contaminants of Emerging Concern (CECs) (Diclofenac-DCF, Sulfamethoxazole-SMX and Trimethoprim-TMP), the removal of antibiotic resistant elements, the residual toxicity and the treatment cost has been analysed. Different PMS concentrations (0–1 mM) were tested and an enhancement in the process performance was obtained with increasing oxidant load, obtaining the best results with 1 mM of PMS, at which detection limit (DL) of 2 CFU/mL was reached for all microbial targets after 15 min (1.1 kJ/L of accumulated solar UV-A radiation (QUV)) and 80 % of CECs removal was reached after 27 min (2.0 kJ/L of QUV) of solar treatment time. Inactivation of naturally occurring antibiotic resistant bacteria (ARB) and removal of 16S rRNA and selected antibiotic resistance genes (ARGs) (i.e., intI1, sul1, qnrS, blaTEM, blaCTX-M32, tetM) were also investigated. ARB was successfully inactivated to values below the DL, but the process was not able to completely remove ARGs. A total reduction of intI1 (30 %), 16S rRNA (19 %), sul1 (14 %), blaCTX-M32 (12 %), qnrS (10 %), blaTEM (8 %), and tetM (7 %), was obtained after 120 min (11.5 kJ/L of QUV). An absence of an eco and phytotoxic effect of treated samples was observed towards Aliivibrio fischeri and three seeds, respectively. Finally, an estimated treatment cost of 0.96 €/m3 for the simultaneous UWW disinfection and decontamination demonstrates the promising capability of this solar treatment for UWW reclamation and reuse in agriculture, especially in areas with a high solar radiation incidence.

Performance improvement of a solar volumetric reactor with passive thermal management under different solar radiation conditions

To alleviate the effect of solar radiation fluctuation on the solar volumetric reactor, phase change material (PCM) is applied to buffer the temperature vibration and improve the stability of thermochemical reactions. In this work, we analyzed the heat flow and distribution characteristics of the conventional double-walled volumetric reactor filled with PCMs (SVR1). We then proposed a novel solar volumetric reactor design (SVR2) to solve the problems of local high temperature, slow charging-discharging rate, and fluctuating methane conversion in various radiation conditions. The heat and mass transfer model coupled with thermochemical reaction kinetics was established to compare the performance of SVR1 and SVR2 under steady state, heat charging-discharging mode, and actual solar radiation fluctuation, respectively. The results show that compared to SVR1, the maximum temperature of SVR2 decreases by 106.3 K, and the minimum methane conversion rate increases from 77.4% to 93.6% under natural solar radiation fluctuation.

Nanosponge-C3N4 composites as photocatalysts for selective partial alcohol oxidation in aqueous suspension.

A set of four composite materials was prepared, consisting of a nanosponge matrix based on β-cyclodextrin in which carbon nitride was dispersed. The materials were characterized by the presence of diverse cross-linker units joining the cyclodextrin moieties, in order to vary the absorption/release abilities of the matrix. The composites were characterized and used as photocatalysts in aqueous medium under UV, visible and natural solar irradiation for the photodegradation of 4-nitrophenol, and for the selective partial oxidation of 5-hydroxymethylfurfural and veratryl alcohol to the corresponding aldehydes. The nanosponge-C3N4 composites showed higher activity than the pristine semiconductor, which can probably be attributed to the synergic effect of the nanosponge, capable of increasing the substrate concentration near the surface of the photocatalyst.

Sustainable Cu2(OH)2CO3/g-C3N4/cellulose acetate-derived porous composite membrane for Congo red and tetracycline removal with photocatalytic self-cleaning properties under natural solar irradiation

A highly efficient and sustainable Cu/CN@CA composite membrane was synthesized for the removal of typical dyes and antibiotics by incorporating a Cu2(OH)2CO3/g-C3N4 heterojunction (Cu/CN) onto a cellulose acetate (CA) membrane. The 0.2Cu/CN@CA membrane with optimized Cu/CN doping achieved superior Congo red (CR) and tetracycline (TC) adsorption capacities of 250.8 and 48.43 mg/g, respectively. Notably, the exhausted 0.2Cu/CN@CA after adsorption saturation could be effectively self-cleaned under natural solar irradiation. Consecutive adsorption-photocatalytic experiments revealed its fine stability and recyclability. Mechanistic exploration based on experimental analysis and DFT (Density Function Theory) calculations revealed that cellulose acetate accommodates the charge transfer interactions between g-C3N4 and Cu2(OH)2CO3, wherein many photogenerated electrons were generated and migrated from g-C3N4 to Cu2(OH)2CO3. This type II heterojunction transfer pathway induced the strong oxidizability of the 0.2Cu/CN@CA membrane with plenty of active species for the photocatalytic degradation of the adsorbed CR and TC contaminants under solar light irritation. This study provided a novel sustainable membrane-based adsorbent for the enhanced dye and antibiotic contaminant remediation of aquatic environments.

PHOTOCATALYTIC DEGRADATION OF LAMBDACYHALOTHRIN (PYRETHROID) IN WASTEWATER USING ZINC OXIDE NANOPARTICLE

Accumulating synthetic pesticides in the living system has brought about several critical alerts from researchers as it interferes with the essential processes in the body. Metal oxide nanoparticles possess suitable properties including band gap and have played an important role in the photocatalytic degradation of toxic chemicals in wastewater and the environment under natural solar radiation. This research aims at the photocatalytic degradation of Type II Pyrethroid Pesticide (Lambda-cyhalothrin) in wastewater and agricultural runoff using Zinc Oxide Nanoparticles. The synthesized ZnO Nanoparticle (NP) was ascertained by characterization using XRD for material crystallinity and crystallite size, SEM, and particle size analysis for surface morphology and size. The EDAX spectra confirmed the presence of Zinc elements and showed that the synthesized zinc oxide nanoparticles were pure. The degradation experiment was conducted under natural solar irradiation. The initial and final/equilibrium concentration of Lambda-cyhalothrin residue were determined using High-performance liquid chromatography (HPLC) followed by computation of degradation capacity. Photocatalytic degradation of LCY was successful following the application of Zinc oxide NPs as nanocatalysts with an efficiency of about 87% as compared to the control. The synthesized Nanoparticle was found to degrade a large percentage of Lambda-cyhalothrin residue in wastewater. Exploiting its application in the remediation of pesticides in agricultural runoff may be crucial at this point.

In-silico STUDIES OF UNIQUE SCHIFF BASE OF BENZIMIDAZOLE DERIVATIVES AS ANTICANCER AGENTS

Accumulating synthetic pesticides in the living system has brought about several critical alerts from researchers as it interferes with the essential processes in the body. Metal oxide nanoparticles possess suitable properties including band gap and have played an important role in the photocatalytic degradation of toxic chemicals in wastewater and the environment under natural solar radiation. This research aims at the photocatalytic degradation of Type II Pyrethroid Pesticide (Lambda-cyhalothrin) in wastewater and agricultural runoff using Zinc Oxide Nanoparticles. The synthesized ZnO Nanoparticle (NP) was ascertained by characterization using XRD for material crystallinity and crystallite size, SEM, and particle size analysis for surface morphology and size. The EDAX spectra confirmed the presence of Zinc elements and showed that the synthesized zinc oxide nanoparticles were pure. The degradation experiment was conducted under natural solar irradiation. The initial and final/equilibrium concentration of Lambda-cyhalothrin residue were determined using High-performance liquid chromatography (HPLC) followed by computation of degradation capacity. Photocatalytic degradation of LCY was successful following the application of Zinc oxide NPs as nanocatalysts with an efficiency of about 87% as compared to the control. The synthesized Nanoparticle was found to degrade a large percentage of Lambda-cyhalothrin residue in wastewater. Exploiting its application in the remediation of pesticides in agricultural runoff may be crucial at this point.

Catalytically transforming cellulose into methane under natural solar irradiation

A green and sustainable catalytic system with Ni/SiO2 as catalyst and solar irradiation as energy for transforming cellulose into methane was developed.

Efficient photodegradation of Victoria Blue B and Acridine Orange dyes by nickel oxide nanoparticles

Nickel oxide (NiO) nanoparticle has been conveniently prepared by solution combustion method using urea as a fuel. Characterization of NiO nanoparticles has been performed by XRD, SEM with EDX, TEM, BET surface area determination, and UV-absorption spectroscopy. The band gap of the nanoparticle is 3.08 eV and average size of the nanoparticle is 26 nm, and the nanoparticles exhibited a cubic structure. Further, TEM confirms the average size is<35 nm. The synthesized nanoparticle has been successfully used against Victoria Blue B (VBB) and Acridine Orange (AO) dye degradation under natural solar irradiation by varying catalyst concentration, pH, and initial dye concentration. The prepared NiO nanoparticles showed excellent photocatalytic degradation of VBB and AO. The degradation efficiency was assessed by varying catalyst concentration, solution pH, and dye concentration. We obtained a high percentage of photodegradation at 1 × 10-4 mol/dm3 dye concentration and pH 4 for both dyes.

Performance analysis of step type solar still and comparison of the performance with evacuated tube collector coupled with single slope step type solar still

This research project aims to address the growing need for freshwater in regions affected by water scarcity, particularly in coastal and desert areas. The focus is on evaluating the effectiveness of a solar-powered desalination system, which utilizes a single slope step type solar still and an Evacuated Tube Collector (ETC) to produce fresh drinkable water. Additionally, Computational Fluid Dynamics (CFD) analysis is conducted to gain insights into the natural convection of heat transfer within a glass tube, which creates a buoyant flow of saline water. The design consists of a solar evacuated tube, which heats up due to the exposure to sun rays and this heat is transferred to the impure/saline water (effluent). The water is then discharged to a single slope step type solar still which absorbs energy from sunlight and increases the evaporation rate in the solar still. Thus, the water evaporates and is then condensed by the inner surface of the glass roof hence purified water is collected. The CFD flow analysis of incompressible fluid under the effect of gravity in the transient condition is carried out for ETC in the ANSYS workbench. Also, fluid flow analysis of single slope step type solar still consisting of ten steps with a water depth of 3 cm in multiphase conditions using the VOF model is carried out to obtain the amount of distillate output per day in fair weather conditions in the location 13.2848⁰ N, 74.7486⁰ E in Katapady, Udupi. The amount of distillate collected as a result of CFD analysis was found to be 5.195 kg/day. The contours obtained from the steady state analysis for solar still showed the distribution of temperature, solar heat flux, and mass flow rate. The transient analysis of the ETC assisted well in obtaining the temperature in the ETC collector tank and the variation in solar radiation throughout the day. The contours of ETC showed the buoyant flow of water under natural convection, velocity distribution, density distribution and solar irradiation distribution on glass walls.

Space-occupied 3D structure improves distilled water collection at the solar interface distillation

Recently, solar-driven interfacial distillation has rapidly developed into an effective technology for unconventional water treatment. Solar evaporator as the central part of the system was extensively investigated and achieved high light-to-heat efficiencies. However, the combination of interfacial evaporators and solar still in the application was rarely studied, and the phenomena inside the device during evaporation have yet to be revealed. Here, we designed an interfacial evaporator with a conical solar still unit to study the enhancement of water collection. The physical changes inside the device during natural solar irradiation were also revealed. In addition, the COMSOL Multiphysics as simulation software was applied to reveal the temperature variation of the system during solar motion. As a result, the condensate collection of the space-occupied 3D system is 2.5 times that of the plant system in the actual solar irradiation, which is even larger than the laboratory irradiation process. In addition to more solar energy absorption during the solar movement, the faster saturation of the humidity (more than 90%) due to the space occupation is also an important factor for the higher water collection capacity of the 3D system. This discovery would provide a reference for the design of the interfacial evaporator and evaporation device in the future and promote its practical application.

Development of Sulfur-Doped Graphitic Carbon Nitride for Hydrogen Evolution under Visible-Light Irradiation.

Developing eco-friendly strategies to produce green fuel has attracted continuous and extensive attention. In this study, a novel gas-templating method was developed to prepare 2D porous S-doped g-C3N4 photocatalyst through simultaneous pyrolysis of urea (main g-C3N4 precursor) and ammonium sulfate (sulfur source and structure promoter). Different content of ammonium sulfate was examined to find the optimal synthesis conditions and to investigate the property-governed activity. The physicochemical properties of the obtained photocatalysts were analyzed by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), scanning transmission electron microscopy (STEM), specific surface area (BET) measurement, ultraviolet-visible light diffuse reflectance spectroscopy (UV/vis DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and reversed double-beam photo-acoustic spectroscopy (RDB-PAS). The as-prepared S-doped g-C3N4 photocatalysts were applied for photocatalytic H2 evolution under vis irradiation. The condition-dependent activity was probed to achieve the best photocatalytic performance. It was demonstrated that ammonium sulfate played a crucial role to achieve concurrently 2D morphology, controlled nanostructure, and S-doping of g-C3N4 in a one-pot process. The 2D nanoporous S-doped g-C3N4 of crumpled lamellar-like structure with large specific surface area (73.8 m2 g-1) and improved electron-hole separation showed a remarkable H2 generation rate, which was almost one order in magnitude higher than that of pristine g-C3N4. It has been found that though all properties are crucial for the overall photocatalytic performance, efficient doping is probably a key factor for high photocatalytic activity. Moreover, the photocatalysts exhibit significant stability during recycling. Accordingly, a significant potential of S-doped g-C3N4 has been revealed for practical use under natural solar radiation.

CdO nanoplates for photocatalytic degradation of Levofloxacin and Nizatidine under natural solar light irradiation

• Preparation of CdO nanoplates via hydrothermal method. • Systematic evaluation for the properties of CdO nanplates . • Evaluation of CdO nanplates photocatalytic activity for the degradation of pharmaceuticals under solar light irradiation. Increasing demand for clean water due to the rapid development of industry, population growth and long-term droughts have become an issue worldwide. Sustainable technologies to address this challenge have epitomised the current trends in environmental research. In this work, three types of cadmium oxide (CdO) photocatalysts with nanoplate like morphology were prepared by a simple hydrothermal method. The prepared samples were characterized by various analytical techniques such as XRD, XPS, UV-DRS, SEM and EDX. XRD studies revealed that the prepared CdO samples were of the cubic phase structure. The grain sizes of CdO nanoplates CdO (1:4), CdO (1:5) and CdO (1:6) were 27.22, 28.29 and 28.41 nm, respectively. XPS and EDS analysis confirmed the stoichiometry of CdO samples. The CdO nanostructures samples possessed band gaps from 2.4 to 2.5 eV and therefore could be activated by solar light. The CdO exhited enhanced photocatalytic performance for the degradation of Nizatidine and Levofloxacin under solar light irradiation and around 80% of the pharmaceuticals were degraded within 4 hrs. These results suggest that CdO will be the promising candidate for the decontamination of hazardous low concentrated pollutions in water.

A Diode‐like Scalable Asymmetric Solar Evaporator with Ultra‐high Salt Resistance

AbstractPassive solar‐driven interfacial evaporation is an environmental‐friendly approach for seawater desalination. However, non‐volatile salts usually precipitate on the evaporator surface during evaporation, significantly reducing the evaporation rate and blocking the evaporator. Although several strategies have been proposed for this issue, they are usually only effective under low salinity conditions and natural solar irradiation. In this study, a scalable solar evaporator is proposed, which is expediently fabricated by carbonizing the commercially available coconut fiber cloth, through designing and optimizing an asymmetric bi‐layer structure with a trapezoidal evaporation surface and a wide leg‐strengthened water supply pathway. Both experimental and simulation results indicate that the evaporator presents ultra‐high salt tolerance, which keeps running steadily for consecutive 14 days under the high salinity of 14 wt% NaCl and high irradiation of 4 suns. This excellent salt resistance arises from a diode‐like ion migration introduced by its asymmetric structure. Meanwhile, a remarkable evaporation rate of 7.28 kg m−2 h−1 is also achieved under the harsh condition, resulting from the high solar absorbance and the reduced evaporation enthalpy of the evaporator. Such an evaporator is confirmed as a simple, low‐cost, scalable, efficient, and long‐term stable device for producing freshwater under harsh desalination conditions.

Microcontaminant removal in solar pilot scale photoreactors with commercial iron nanoparticles obtained from olive mill wastewater

This study assessed removal of microcontaminants (MCs) from natural water (NW) using iron nanoparticles extracted from olive mill wastewater (ZVI-OMW), an agro-industrial waste product, combined with oxidants under natural solar radiation. The specific effects of corrosion, adsorption and solar photolysis, and of H2O2, S2O82-, carbonates and ZVI-OMW concentrations on treatment efficiency were also evaluated. Lab tests demonstrated that the combination of 1 mM S2O82- with NW and 1 mM ZVI-OMW was the best treatment option. Process performance was evaluated under these operating conditions in pilot-scale raceway pond reactors (RPR) at three liquid depths (5, 10 and 15 cm), as well as in a compound parabolic collector (CPC) photo-reactor. The time required to achieve 50% removal of a MC mixture (atrazine, carbendazim, imidacloprid and thiamethoxam, at 100 µg/L each) increased with liquid depth, resulting in 164, 224, and 250 min for 5, 10, and 15 cm, respectively. MC mass removal rate increased with liquid depth, achieving 50% MC removal in the CPC (1 mM ZVI-OMW) in 120 min. Doubling ZVI-OMW concentration was detrimental to process efficiency in both photoreactors due to light obstruction. Partial sedimentation of ZVI-OMW in the RPR suggests that the use of this type of reactor for heterogeneous photocatalysis could present problems for large-size operation.

Continuous flow photocatalytic reactor using TiO2‐coated foams, modeling and experimental operating mode

AbstractThis article aims to build a modeling and simulating tool of the operation of a continuous flow heterogeneous photocatalysis reactor. Continuous flow is well‐known in reactor engineering for allowing advanced control of reactor and scaling‐up with great confidence, but little research has addressed it's potential for this kind of application. In developing this model, particular attention was paid to the coupling which occurs at local scale between the radiative transfer and the reaction kinetics of advanced oxidation of a target organic micro‐pollutant. The solution of the radiative transfer equation by Monte Carlo method was applied to a photocatalyst supported on a macroporous ceramic foam forming an efficient 3D support. After identification of the kinetic law of degradation, the dynamic simulation model was validated through comparison with a series of experiments performed for different but constant irradiations and for variable irradiations approaching, in term of intensity and dynamics, natural solar radiation.

Wavelength Dependence of the Photocatalytic Performance of Pure and Doped TiO2 Photocatalysts—A Reflection on the Importance of UV Excitability

The photocatalytic performances of doped and non-doped TiO2 photocatalysts (TiO2-s) were compared under solar and various types of artificial irradiation using phenol as a model contaminant. Non-doped (mainly anatase phase) TiO2-s had significantly higher photocatalytic efficiency than highly visible-light-active TiO2-s under natural solar irradiation. To explain these unexpected results, we measured the wavelength dependence of photocatalytic efficiency at six different wavelength ranges (λ = 300–650 nm). For this purpose, UV fluorescence tubes and five LED lights of different colors (violet, blue, green, yellow, and red) were used to activate the photocatalysts. The photon fluxes of the irradiation were measured, and apparent quantum yields were calculated for all irradiation conditions. The highest apparent quantum yield was 1.43% for our own TiO2 (prepared via flame hydrolysis) under UV irradiation. However, apparent quantum yields were significantly lower (by 1–2 orders of magnitude) in the visible range, even for the most visible-light-active TiO2.

Finite Difference Modeling of the Temperature Profile during the Biodrying of Organic Solid Waste

Biodrying is a complex process that is very useful in the treatment of solid waste, where variables, such as temperature, thermal conductivity and the moisture content of organic matter, oxygen concentration in the pore space of the waste mass, microbial heat generation, microbial biomass, among others, are involved. Given this complexity, the development of mathematical models that help us to understand this bioprocess is fundamental. In the present work, a mathematical model, based on the finite difference method, was developed to predict the temperature profile at nine recording points, in an organic solid waste pile, during the biodrying process. The bioprocess was carried out under natural convection and solar radiation conditions, inside a greenhouse-type structure. A network of 53 nodes, distributed in the x, y and z directions, on a rectangular prism, was developed. From this network, 27 base nodes were taken and the energy balance was developed for each node, and with this, the equation was obtained, in explicit form, to calculate the temperature. In these base equations, the microbial heat generation was considered, at between 2 and 140 W/m3; the convective coefficient was between 1 and 5 W/m2 °C; and the daily records were taken inside the greenhouse for the solar radiation (0 to 450 W/m2), temperature (15 to 50 °C) and RH% (70 to 30). The modeled temperature profiles of the center (C) and the midpoints of the pile were, on average, 91% close to the experimental values, during the period from 0 to 20 days of biodrying; 70% close, during the period from day 21 to 35, the period when the modeled values were lower, due to the turning of the pile; and 94% close to the experimental values from day 36 to 50, when the modeled values were higher, also due to turning. The modeled temperature profiles of the left, right, upper and lower surfaces were, on average 92% close to the experimental profiles over the 0–35 day period, and the modeled and experimental values were practically identical from day 36 to 50 of the biodrying process.