Solar wastewater treatment plant for aqueous solution of pesticide

A pesticide (Vydine) considered priority substances by the Jordanian environment ministry and dissolved in water at 25 mg L⁻¹ (or at maximum water solubility) has been degraded at solar pilot plant scale using direct solar UV-light, solar UV combined with H₂O₂ or Fe(II) and solar photo-Fenton. Two different solar irradiation conditions (med day irradiation under clear sky and late hour irradiation under clear sky) have been tested and discussed, using mainly pesticide concentration, TOC mineralization, COD removal and BOD for comparison of treatment effectiveness. A cute toxicity assays were also employed for evaluating the photocatalytic treatments, and comparison between these results. Direct solar UV photolysis is less efficient in term of pesticide degradation than other AOP’s. In contrast, solar photo-Fenton reaction produced higher pesticide degradation in a shorter time (40 min was sufficient for 88% pesticide removal with 20 mg L⁻¹ H₂O₂ and 20 mg L⁻¹ Fe (II)). In these conditions, the BOD₅ was increased from zero for pure pesticide solution to 54 mg O₂/L and acute toxicity was decreased from 19 to 6 toxicity unit.     

p-Cu2O/n-ZnO heterojunction applied to visible light Orange II degradation

The p-Cu₂O/n-ZnO system is studied for its potential use as a photoactive heterojunction able to highly perform under visible light. The main application deals with the degradation of organic dyes such as Orange II and the effects of Cu₂O amount, Orange II concentration and light intensity are investigated. Results show that the kinetics of degradation follows a pseudo-first order and the optimum sensitization effect is obtained using a 70% concentration of Cu₂O. The degradation rate reaches its maximum (R_initial = 22.45 × 10⁻² mg l⁻¹ min⁻¹) at 15 mg l⁻¹ of Orange II. The effect of the irradiation intensity is also investigated taking the electrical energy consumption per order of magnitude (EE/O) as a figure of merit. The highest efficiency is obtained at an irradiation intensity of ∼122 × 10⁻⁵ kW with k_OBS = 14.97 × 10⁻³ min⁻¹ and EE/O, which corresponds to 12.54 kW h m⁻³ of energy consumption. This heterojunction allows a ∼25% saving of electrical energy in comparison to the p-Cu₂O/n-TiO₂ system, demonstrating the important role of the collector.     

Potential benefits of solar reflective car shells: Cooler cabins,fuel savings and emission reductions

Vehicle thermal loads and air conditioning ancillary loads are strongly influenced by the absorption of solar energy. The adoption of solar reflective coatings for opaque surfaces of the vehicle shell can decrease the “soak” temperature of the air in the cabin of a vehicle parked in the sun, potentially reducing the vehicle’s ancillary load and improving its fuel economy by permitting the use of a smaller air conditioner. An experimental comparison of otherwise identical black and silver compact sedans indicated that increasing the solar reflectance (ρ) of the car’s shell by about 0.5 lowered the soak temperature of breath-level air by about 5–6 °C. Thermal analysis predicts that the air conditioning capacity required to cool the cabin air in the silver car to 25 °C within 30 min is 13% less than that required in the black car. Assuming that potential reductions in AC capacity and engine ancillary load scale linearly with increase in shell solar reflectance, ADVISOR simulations of the SC03 driving cycle indicate that substituting a typical cool-colored shell (ρ = 0.35) for a black shell (ρ = 0.05) would reduce fuel consumption by 0.12 L per 100 km (1.1%), increasing fuel economy by 0.10 km L⁻¹ [0.24 mpg] (1.1%). It would also decrease carbon dioxide (CO₂) emissions by 2.7 g km⁻¹ (1.1%), nitrogen oxide (NO_x) emissions by 5.4 mg km⁻¹ (0.44%), carbon monoxide (CO) emissions by 17 mg km⁻¹ (0.43%), and hydrocarbon (HC) emissions by 4.1 mg km⁻¹ (0.37%). Selecting a typical white or silver shell (ρ = 0.60) instead of a black shell would lower fuel consumption by 0.21 L per 100 km (1.9%), raising fuel economy by 0.19 km L⁻¹ [0.44 mpg] (2.0%). It would also decrease CO₂ emissions by 4.9 g km⁻¹ (1.9%), NO_x emissions by 9.9 mg km⁻¹ (0.80%), CO emissions by 31 mg km⁻¹ (0.79%), and HC emissions by 7.4 mg km⁻¹ (0.67%). Our simulations may underestimate emission reductions because emissions in standardized driving cycles are typically lower than those in real-world driving.     

Treatment of textile wastewaters by solar-driven advanced oxidation processes

Heterogeneous (TiO₂/UV, TiO₂/H₂O₂/UV) and homogenous (H₂O₂/UV, Fe²⁺/H₂O₂/UV) solar advanced oxidation processes (AOPs) are proposed for the treatment of recalcitrant textile wastewater at pilot-plant scale with compound parabolic collectors (CPCs). The textile wastewater presents a lilac colour, with a maximum absorbance peak at 516 nm, high pH (pH = 11), moderate organic content (DOC = 382 mg C L⁻¹, COD = 1020 mg O₂ L⁻¹) and high conductivity (13.6 mS cm⁻¹), associated with a high concentration of chloride (4.7 g Cl⁻ L⁻¹). The DOC abatement is similar for the H₂O₂/UV and TiO₂/UV processes, corresponding only to 30% and 36% mineralization after 190 kJ_UV L⁻¹. The addition of H₂O₂ to TiO₂/UV system increased the initial degradation rate more than seven times, leading to 90% mineralization after exposure to 100 kJ_UV L⁻¹. All the processes using H₂O₂ contributed to an effective decolourisation, but the most efficient process for decolourisation and mineralization was the solar-photo-Fenton with an optimum catalyst concentration of 100 mg Fe²⁺ L⁻¹, leading to 98% decolourisation and 89% mineralization after 7.2 and 49.1 kJ_UV L⁻¹, respectively. According to the Zahn-Wellens test, the energy dose necessary to achieve a biodegradable effluent after the solar-photo-Fenton process with 100 mg Fe²⁺ L⁻¹ is 12 kJ_UV L⁻¹.     

Inactivation of Clostridium perfringens spores and vegetative cells by photolysis and TiO2 photocatalysis with H2O2

Due to public health concerns related to the generation of dangerous by-products from conventional systems of water disinfection, innovative technologies based on the generation of oxidant radicals are being developed. The aim of this work is to evaluate the bactericidal activity of different treatments with light (λ: 320-800 nm), TiO₂ (1 g L⁻¹) and H₂O₂ (0.04 mM) on the viability of vegetative cells and spores of Clostridium perfringens. After spiking a natural water sample (from the Ebro River, Zaragoza (Spain)), the population of vegetative cells was of 10⁸ CFU·100 mL⁻¹ and of spores about 10³ CFU·100 mL⁻¹. Treatments without radiation source (TiO₂, H₂O₂, TiO₂/H₂O₂) show a poor level of inactivation (<0.5 log) on both bacterial forms. The light treatment achieves a vegetative cell inactivation of 1.2 log after 5 min of treatment and <0.5 log on spores after 30 min. The combined light/TiO₂ system increases the level of disinfection with a vegetative cell removal in the order of 6 log after 5 min and 0.6 log of spores after 5 min. Light/H₂O₂ and light/TiO₂/H₂O₂ treatments also significantly increase the disinfection of vegetative cells of C. perfringens (>6 log). Regarding spores, light/H₂O₂ and light/TiO₂/H₂O₂ treatments achieve constant inactivation of 1 log after 5 min of treatment. The application of a light/TiO₂/H₂O₂ treatment does not increase the level of inactivation with regard to the level reached by the light/TiO₂ and light/H₂O₂ systems. This fact shows there is no a significant interaction between TiO₂ and H₂O₂ under the conditions studied.     

Bio-hydrogen production by photo-fermentation of dark fermentation effluent with intermittent feeding and effluent removal

Pure culture of Rhodobacter sphaeroides (NRRL- B1727) was used for continuous photo-fermentation of volatile fatty acids (VFA) present in the dark fermentation effluent of ground wheat starch. The feed contained 1950 ± 50 mg L⁻¹ total VFA with some nutrient supplementation. Hydraulic residence time (HRT) was varied between 24 and 120 hours. The highest steady-state daily hydrogen production (55 ml d⁻¹) and hydrogen yield (185 ml H₂ g⁻¹ VFA) were obtained at HRT = 72 hours (3 days). Biomass concentration increased with increasing HRT. Volumetric and specific hydrogen formation rates were also maximum at HRT = 72 h. High extent of TVFA fermentation at HRT = 72 h resulted in high hydrogen gas production.     

Application of sweet sorghum for biodiesel production by heterotrophic microalga Chlorella protothecoides

Microalga Chlorella protothecoides can grow heterotrophically with glucose as the carbon source and accumulate high proportion of lipids. The microalgal lipids are suitable for biodiesel production. To further increase lipid yield and reduce biodiesel cost, sweet sorghum juice was investigated as an alternative carbon source to glucose in the present study. When the initial reducing sugar concentration was 10 g L⁻¹ in the culture medium, the dry cell yield and lipid content were 5.1 g L⁻¹ and 52.5% using enzymatic hydrolyzates of sweet sorghum juice as the carbon source after 120 h-culture in flasks. The lipid yield was 35.7% higher than that using glucose. When 3.0 g L⁻¹ yeast extract was added to the medium, the dry cell yield and lipid productivity was increased to 1.2 g L⁻¹ day⁻¹ and 586.8 mg L⁻¹ day⁻¹. Biodiesel produced from the lipid of C. protothecoides through acid catalyzed transesterification was analyzed by GC–MS, and the three most abundant components were oleic acid methyl ester, cetane acid methyl ester and linoleic acid methyl ester. The results indicate that sweet sorghum juice could effectively enhance algal lipid production, and its application may reduce the cost of algae-based biodiesel.     

Biological hydrogen production from corn stover by moderately thermophile Thermoanaerobacterium thermosaccharolyticum W16

This study addressed the utilization of an agro-waste, corn stover, as a renewable lignocellulosic feedstock for the fermentative H₂ production by the moderate thermophile Thermoanaerobacterium thermosaccharolyticum W16. The corn stover was first hydrolyzed by cellulase with supplementation of xylanase after delignification with 2% NaOH. It produced reducing sugar at a yield of 11.2 g L⁻¹ glucose, 3.4 g L⁻¹ xylose and 0.5 g L⁻¹ arabinose under the optimum condition of cellulase dosage 25 U g⁻¹ substrate with supplement xylanase 30 U g⁻¹ substrate. The hydrolyzed corn stover was sequentially introduced to fermentation by strain W16, where, the cell density and the maximum H₂ production rate was comparable to that on simulated medium, which has the same concentration of reducing sugars with hydrolysate. The present results suggest a promising combined hydrogen production process from corn stover with enzymatic hydrolysis stage and fermentation stage using W16.     

Light fermentation of dark fermentation effluent for bio-hydrogen production by different Rhodobacter species at different initial volatile fatty acid (VFA) concentrations

Three different Rhodobacter sphaeroides (RS) strains (RS–NRRL, RS–DSMZ and RS–RV) and their combinations were used for light fermentation of dark fermentation effluent of ground wheat containing volatile fatty acids (VFA). In terms of cumulative hydrogen formation, RS–NRRL performed better than the other two strains producing 48 ml H₂ in 180 h. However, RS–RV resulted in the highest hydrogen yield of 250 ml H₂ g⁻¹ TVFA. Specific hydrogen production rate (SHPR) with the RS–NRRL was also better in comparison to the others (13.8 ml H₂ g⁻¹ biomass h⁻¹). When combinations of those three strains were used, RS–RV + RS–DSMZ resulted in the highest cumulative hydrogen formation (90 ml H₂ in 330 h). However, hydrogen yield (693 ml H₂ g⁻¹ TVFA) and SHPR (12.1 ml H₂ g⁻¹ biomass h⁻¹) were higher with the combination of the three different strains. On the basis of Gompertz equation coefficients mixed culture of the three different strains gave the highest cumulative hydrogen and formation rate probably due to synergistic interaction among the strains. The effects of initial TVFA and NH₄–N concentrations on hydrogen formation were investigated for the mixed culture of the three strains. The optimum TVFA and NH₄–N concentrations maximizing the hydrogen formation were determined as 2350 and 47 mg L⁻¹, respectively.     

Ammonia inhibition of electricity generation in single-chambered microbial fuel cells

Batch experiments are conducted at various concentrations of initial total ammonia nitrogen (TAN) with acetate as an electron donor to examine the effects of free ammonia (NH₃) inhibition on electricity production in single-chambered microbial fuel cells (MFCs). This research demonstrates that initial TAN concentrations of over 500 mg N L⁻¹ significantly inhibit electricity generation in MFCs. The maximum power density of 4240 mW m⁻³ at 500 mg N L⁻¹ drastically decreases to 1700 mW m⁻³ as the initial TAN increases up to 4000 mg N L⁻¹. Nitrite and nitrate analysis confirms that nitrification after complete acetate removal consumes some TAN. Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) are also inhibited by increasing the initial TAN concentrations. Another batch experiment verifies the strong inhibitory effect of TAN with only small differences between the half-maximum effective concentration (EC₅₀) for TAN (894 mg N L⁻¹ equivalent to 10 mg N L⁻¹ as NH₃) and optimum TAN conditions; it requires careful monitoring of the TAN for MFCs. In addition, abiotic control experiments reveal that granular activated carbon, which is used as an auxiliary anode material, adsorbs a significant amount of ammonia at each TAN concentration in batch MFCs.     

Temperature dependence of Cu2ZnSn(SexS1−x)4 monograin solar cells

The temperature dependence of open-circuit voltage (V_oc), short-circuit current (I_sc), fill factor (FF), and relative efficiency of monograin Cu₂ZnSn(Se_xS_1−x)₄ solar cell was measured. The light intensity was varied from 2.2 to 100 mW/cm² and temperatures were in the range of T = 175-300 K. With a light intensity of 100 mW/cm²dV_oc/dT was determined to be −1.91 mV/K and the dominating recombination process at temperatures close to room temperature was found to be related to the recombination in the space-charge region. The solar cell relative efficiency decreases with temperature by 0.013%/K. Our results show that the diode ideality factor n does not show remarkable temperature dependence and slightly increases from n = 1.85 to n = 2.05 in the temperature range between 175 and 300 K.     

Response of H2 production and Hox-hydrogenase activity to external factors in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803

The effects of external factors on both H₂ production and bidirectional Hox-hydrogenase activity were examined in the non-N₂-fixing cyanobacterium Synechocystis PCC 6803. Exogenous glucose and increased osmolality both enhanced H₂ production with optimal production observed at 0.4% and 20 mosmol kg⁻¹, respectively. Anaerobic condition for 24 h induced significant higher H₂ase activity with cells in BG11₀ showing highest activities. Increasing the pH resulted in an increased Hox-hydrogenase activity with an optimum at pH 7.5. The Hox-hydrogenase activity gradually increased with increasing temperature from 30 ^○C to 60 ^○C with the highest activity observed at 70 ^○C. A low concentration at 100 μM of either DTT or β-mercaptoethanol resulted in a minor stimulation of H₂ production. β-Mercaptoethanol added to nitrogen- and sulfur-deprived cells stimulated H₂ production significantly. The highest Hox-hydrogenase activity was observed in cells in BG11₀-S-deprived condition and 750 μM β-mercaptoethanol measured at a temperature of 70 °C; 14.32 μmol H₂ mg chl a⁻¹ min⁻¹.     

Highly enhanced p-type electrical conduction in wide band gap Cu1+xAl1−xS2 polycrystals

As potential critical p-type transparency electrode materials applied in solar cells, a series of the Cu- and Zn-doped CuAlS₂ samples with band gaps over 3 eV have been prepared, and their optical and electrical properties have been thoroughly investigated. Conductivities as high as 250 S cm⁻¹ are achieved at a Cu doping level of 8 mol%, which are among the highest values known for p-type transparent materials and sufficient for collecting holes in solar cells. A high mobility of 21.2 cm² V⁻¹ s⁻¹ is also reached at the same doping level. The origin of conductivity enhancement by Cu doping and the structure-optoelectrical property relationship has been elucidated.     

La1−xSrxCoO3 (x = 0.1-0.5) as the cathode catalyst for a direct borohydride fuel cell

Direct borohydride fuel cells (DBFCs), with a series of perovskite-type oxides La_1−xSr_xCoO₃ (x = 0.1-0.5) as the cathode catalysts and a hydrogen storage alloy as the anode catalyst, are studied in this paper. The structures of the perovskite-type catalysts are mainly La_1−xSr_xCoO₃ (_x = 0.1-0.5) oxides phases. However, with the increase of strontium content, the intensities of the X-ray diffraction peaks of the impure phases La₂Sr₂O₅ and SrLaCoO₄ are gradually enhanced. Without using any precious metals or expensive ion exchange membranes, a maximum current density of 275 mA cm⁻² and a power density of 109 mW cm⁻² are obtained with the Sr content of x = 0.2 at 60 °C for this novel type of fuel cell.     

Decontamination of cork wastewaters by solar-photo-Fenton process using cork bleaching wastewater as H2O2 source

This paper reports on a treatment strategy of cork wastewaters through the design of a solar-photo-Fenton process using cork bleaching wastewater as hydrogen peroxide (H₂O₂) source, as a pre-oxidation step, before a conventional biological oxidation process. This method proved to be efficient, achieving mineralization rates higher than 90% for different iron concentrations (20-80 mg Fe L⁻¹). Higher iron concentrations resulted in the lower energy consumption and 60 mg Fe L⁻¹ was selected as the optimum dose for 91% mineralization and used for biodegradability studies. According to the Zahn-Wellens test, the optimum phototreatment energy to achieve a biodegradable effluent is 13.6 kJ_UV L⁻¹ (65% mineralization), which corresponds to H₂O₂ consumption of 76.1 mM (approximately 8.5 L of cork bleaching wastewater (at 7.7 g H₂O₂ L⁻¹) for 15 L of cork boiling wastewater).     

Ionic liquid electrolyte based on S-propyltetrahydrothiophenium iodide for dye-sensitized solar cells

A new ionic liquid S-propyltetrahydrothiophenium iodide (T₃I) was developed as the solvent and iodide ion source in electrolyte for dye-sensitized solar cells. The electrochemical behavior of the /I⁻ redox couple and effect of additives in this ionic liquid system was tested and the results showed that this ionic liquid electrolyte revealed good conducting abilities and potential application for solar devices. The effects of LiI and dark-current inhibitors were investigated. The dye-sensitized solar cell with the electrolyte (0.1 mol L⁻¹ LiI, 0.35 mol L⁻¹ I₂, 0.5 mol L⁻¹ NMBI in pure T₃I) gave short-circuit photocurrent density (J_sc) of 11.22 mA cm², open-circuit voltage (V_oc) of 0.61 V and fill factor (FF) of 0.51, corresponding to the photoelectric conversion efficiency (η) of 3.51% under one Sun (AM1.5).     

Dye-sensitized, nano-porous TiO2 solar cell with poly(acrylonitrile): MgI2 plasticized electrolyte

Dye-sensitized solar cells are promising candidates as supplementary power sources; the dominance in the photovoltaic field of inorganic solid-state junction devices is in fact now being challenged by the third generation of solar cells based on dye-sensitized, nano-porous photo-electrodes and polymer electrolytes. Polymer electrolytes are actually very favorable for photo-electrochemical solar cells and in this study poly(acrylonitrile)-MgI₂ based complexes are used. As ambient temperature conductivity of poly(acrylonitrile)-salt complexes are in general low, a conductivity enhancement is attained by blending with the plasticizers ethylene carbonate and propylene carbonate. At 20 °C the optimum ionic conductivity of 1.9 × 10⁻³ S cm⁻¹ is obtained for the (PAN)₁₀(MgI₂)_n(I₂)_n/10(EC)₂₀(PC)₂₀ electrolyte where n = 1.5. The predominantly ionic nature of the electrolyte is seen from the DC polarization data. Differential scanning calorimetric thermograms of electrolyte samples with different MgI₂ concentrations were studied and glass transition temperatures were determined. Further, in this study, a dye-sensitized solar cell structure was fabricated with the configuration Glass/FTO/TiO₂/Dye/Electrolyte/Pt/FTO/Glass and an overall energy conversion efficiency of 2.5% was achieved under solar irradiation of 600 W m⁻². The I-V characteristics curves revealed that the short-circuit current, open-circuit voltage and fill factor of the cell are 3.87 mA, 659 mV and 59.0%, respectively.     

Phase stability and conductivity of Ba1−ySryCe1−xYxO3−δ solid oxide fuel cell electrolyte

The structure, phase stability, and electrical properties of BaCe_1−xY_xO_3−δ (x = 0-0.4) in humidity air and CO₂ atmosphere are investigated. XRD results indicate that the BaCe_0.9Y_0.1O_3−δ sample has a symmetric cubic structure, and its phase changes to tetragonal as the Y³⁺ doping amount increases to 20 mol%. The conductivity of BaCe_1−xY_xO_3−δ increases with temperature, and it depends on the amount of yttrium doping and the atmosphere. BaCe_0.8Y_0.2O_3−δ exhibits the highest conductivity of 0.026 S cm⁻¹ at 750 °C. The activation energy for conductivity depends on yttrium doping amount and temperature. The conductivity of BaCe_0.8Y_0.2O_3−δ is 0.025 S cm⁻¹ in CO₂ atmosphere at 750 °C which is 3.8% lower than that in air due to reactions with CO₂ and BaCO₃ and the CeO₂ impure phases formed. The structure of BaCe_0.8Y_0.2O_3−δ is unstable in water and decomposes to Ba(OH)₂ and CeO₂ phases. It is found that the activation energy of samples in CO₂ atmosphere is higher than that of sample in air. Sr-doped Ba_1−ySr_yCe_0.8Y_0.2O_3−δ (y = 0-0.2) is prepared to improve the phase stability of BaCe_0.8Y_0.2O_3−δ in water. The conductivity of Ba_0.9Sr_0.1Ce_0.8Y_0.2O_3−δ is 0.023 S cm⁻¹ at 750 °C which was 11% lower than that of BaCe_0.8Y_0.2O_3−δ, however, the phase stability of Ba_0.9Sr_0.1Ce_0.8Y_0.2O_3−δ is much better than that of BaCe_0.8Y_0.2O_3−δ in water.     

Atomic structure of cobalt-oxide nanoparticles active in light-driven catalysis of water oxidation

The atomic structure of water-oxidizing nanoparticles (10–60 nm) formed from cobalt(II) salts and methylenediphosphonate (M2P) is investigated. These amorphous nanoparticles are of high interest for production of solar fuels. They facilitate water oxidation in a directly light-driven process using [Ru(bpy)₃]²⁺ (bpy = 2,2’-bipyridine) as a photosensitizer and persulfate (S₂O₈²⁻) as an electron acceptor. By X-ray absorption spectroscopy (XAS) at the cobalt K-edge, cobalt L-edge and oxygen K-edge, we investigate the light-driven transition from the Co^II/M2P precursor to the active catalyst, which is a layered cobalt(III) oxide with structural similarities to water-oxidizing electrocatalysts. The M2P ligand likely binds at the periphery of the nanoparticles, preventing their further agglomeration during the catalytic reaction. This system opens a possibility to link the catalytically active nanoparticles via a covalent bridge to a photosensitizer and build an artificial photosynthetic system for direct utilization of solar energy for fuel production without production of electricity as an intermediate step.     

Selection of yeast strains for alcoholic fermentation of sugar beet thick juice and green syrup

Presented work aimed at determination of effect of various strains of yeast Saccharomyces cerevisiae and concentration of fermentation worts on dynamics and efficiency of alcoholic fermentation. Fermentation worts contained either thick juice or green syrup.It was found that yeast strains designated as M₁, M₂ and D-2 most efficiently fermented thick juice worts inoculated with yeast cream at a rate of 2 kg m⁻³ of wort. Fermentation processes lasted for approximately 2 days and ethanol yield approached 92-94% of the theoretical yield. Fermentations of green syrup worts were most efficient (ethanol yield reached 90-92% of the theoretical yield) when these processes were carried out by yeast strains M₁, M₂, D-2 and As4 (inoculum - 2 kg m⁻³ of wort).S. cerevisiae strains M₁ and M₂ dynamically and efficiently fermented thick juice worts with extract of 200 g kg⁻¹ and 250 g kg⁻¹ (89-94% of the theoretical yield) while strain D-2 preferred less dense worts (extract of 200 g kg⁻¹) and produced ethanol with the yield of over 92% of the theoretical yield. The optimum green syrup worts extract was 200 g kg⁻¹.