An Overview on the Treatment and Management of the Desalination Brine Solution

Due to the increasing limitations of water resources, application of desalination plants is expanding. One of the constraints associated with desalination plant operation is the production of concentrated solution, which is known as brine and can lead to critical challenges in the environment due to its high level of salinity. In this regard, many different disposal options used recently to control and prevent the environmental issues may be caused by the brine. Evaporation ponds, surface water discharge, and deep well injection are considered as the most well-known options to properly dispose concentrated brine. However, the application of these methods is highly restricted by capital cost and their limited uses. The treatment methods vary in terms of their ability in organics removal and can be divided into three different conventional groups as biological, physicochemical, and oxidation. In recent years, more attention has been paid to membrane-based technologies due to their economic performance in recovering precious resources and providing potable water with high recovery rates. This book chapter provides some critical reviews on recent technologies including treatment operations and disposal options to manage concentrated solutions from desalination plants. Finally, electrodialysis, forward osmosis, and membrane distillation as emerging membrane processes are examined in this chapter

Fabrication and characterization of CuO based heterojunction solar cells

Cupric oxide (CuO) is one of the potential candidates for photovoltaic (PV) industry because of its exceptional electronic and optical properties. Despite attempts by several researchers improve the performance of the CuO-based solar cells, both Voc and Jsc remain low for practical applications. The quality of CuO and the interface quality at the p/n junction are crucial. Lower carrier concentration, higher series resistance of absorber layer and poor carrier collection efficiency are the possible reasons for lower conversion efficiency these solar cells In this thesis, the influence of CuO absorber quality and heterojunction interface properties on the efficiency of CuO based heterojunction solar cell are investigated in detail. Novel layer designs have been used to enhance the carrier collection efficiency of p-CuO/n-Si heterojunction solar cells by studying a series of layer structures prepared by sputtering method. The optical, electrical, microstructural, material quality, chemical composition, surface morphology and photovoltaic properties have been systematically investigated. It is shown that the material quality of the deposited films and interface properties at p-n heterojunction can be significantly improved by tuning the sputtering power and working pressure during the film deposition. A two-step sputter deposition method was adopted to reduce the effect of poor interface quality due to Cu-rich interlayer at the heterojunction. In addition, the effect of Ti doping to improve the conductivity of the CuO films has been studied to obtain lower sheet resistance in CuO films, while retaining the optical properties and crystal quality. Photovoltaic properties with a VOC of 421 mV, JSC of 4.5 mA/cm2 and a photocurrent of 8.3 mA/cm2 have been achieved for p-CuO/n-Si heterojunction solar cells. The efficiency of the device is about 1.21%, which is the highest reported value. Further, a novel method has been demonstrated to obtain significantly higher short-circuit current and fill-factor with front surface field (FSF) design, using Al followed by N doping of the CuO layer. The improvement in Jsc and FF is attributed to the enhancement of charge carrier collection and increase in the carrier concentration. Finally, a new compact model has been proposed for easily predicting the physical parameters of solar cells focusing the improvement of predicted series resistance. It has been shown that the proposed compact model could predict the physical parameters with high accuracy, using several examples.DOCTOR OF PHILOSOPHY (EEE

Defect analysis of sputter grown cupric oxide for optical and electronics application

We have studied the defect density and defect level of sputter grown cupric oxide (CuO) for optical and electronic applications. A deep level transient spectroscopy (DLTS) technique has been employed to study the defect density in the CuO thin film deposited by sputtering. The DLTS studied showed that the defect density significantly reduced for the film grown at a high working pressure. It has also been shown that doping density increases for the film grown at a high working pressure. Transmission electron microscopy analysis revealed the improvement of the crystal quality of the CuO thin film prepared at the high working pressure. The band gap of sputter grown CuO was found to be ~1.4 eV with an absorption coefficient of ~104 cm−1. From a photoelectron spectroscopy measurement, it was found that the work function for CuO was ~5.2 eV. The present work reveals the importance of CuO for optical and electronic device applications

Synthesis of Self-Gravity Settling Faceted-Anatase TiO2 with Dominant {010} Facets for the Photocatalytic Degradation of Acetaminophen and Study of the Type of Generated Oxygen Vacancy in Faceted-TiO2

In this study, faceted TiO2, predominately exposed with {010} facets (T-{010}), was synthesized with a two-step hydrothermal reaction and used for the degradation of acetaminophen (ACE) in an aqueous solution. T-{010} showed considerable photocatalytic reactivity, and its easy-settling (gravity-settling, ~97% of T-{010} settled after 30 min) property demonstrated acceptable reusability. A solid-state chemical reduction approach (NaBH4) at a mild temperature (300 °C) was used for generation of an oxygen vacancy in T-{010} and P25 (commercial TiO2). The oxygen vacancy concentrations of the samples were investigated by electron paramagnetic resonance (EPR). It was also found that NaBH4 reduction induced the generation of both surface and subsurface Ti3+ on colored P25, but only surface Ti3+ species were formed on colored T-{010}. The prepared colored TiO2 samples were successfully used for photocatalytic degradation of ACE in an aqueous solution under visible light illumination

Current Status and Future Prospects of Copper Oxide Heterojunction Solar Cells

The current state of thin film heterojunction solar cells based on cuprous oxide (Cu2O), cupric oxide (CuO) and copper (III) oxide (Cu4O3) is reviewed. These p-type semiconducting oxides prepared by Cu oxidation, sputtering or electrochemical deposition are non-toxic, sustainable photovoltaic materials with application potential for solar electricity. However, defects at the copper oxide heterojunction and film quality are still major constraining factors for achieving high power conversion efficiency, η. Amongst the Cu2O heterojunction devices, a maximum η of 6.1% has been obtained by using pulsed laser deposition (PLD) of AlxGa1−xO onto thermal Cu2O doped with Na. The performance of CuO/n-Si heterojunction solar cells formed by magnetron sputtering of CuO is presently limited by both native oxide and Cu rich copper oxide layers at the heterointerface. These interfacial layers can be reduced by using a two-step sputtering process. A high η of 2.88% for CuO heterojunction solar cells has been achieved by incorporation of mixed phase CuO/Cu2O nanopowder. CuO/Cu2O heterojunction solar cells fabricated by electrodeposition and electrochemical doping has a maximum efficiency of 0.64% after surface defect passivation and annealing. Finally, early stage study of Cu4O3/GaN deposited on sapphire substrate has shown a photovoltaic effect and an η of ~10−2%

Reduction of Cu-rich interfacial layer and improvement of bulk CuO property through two-step sputtering for p-CuO/n-Si heterojunction solar cell

Copper-rich interfacial-layer (Cu-rich IL) is formed during sputter deposition of cupric oxide (CuO) layer on silicon (Si). It has significant impact on the performance of p-CuO/n-Si heterojunction solar cells. In this report, CuO films deposited on Si at different RF-power levels using single and two-step RF-sputtering techniques and p-CuO/n-Si heterojunction solar cells have been investigated. Systematic characterization using XPS, AFM, XRD, Raman, and HR-TEM reveal that two-step RF-sputtering technique offers better crystal quality CuO film with thinner Cu-rich IL layer. Photovoltaic (PV) properties with an open-circuit voltage (Voc ) of 421 mV, short circuit current (Jsc ) of 4.5 mA/cm2, and a photocurrent of 8.3 mA/cm2 have been achieved for the cells prepared using two-step sputtering method, which are significantly higher than that for the solar cells fabricated using a single-step sputtering. The PV properties were further improved by depositing CuO films at higher working pressure with nitrogen doping. The efficiency of the best device achieved is approximately 1.21%, which is the highest value reported for p-CuO/n-Si heterojunction based solar cells.Published versio

Evaluation of Solar-Driven Photocatalytic Activity of Thermal Treated TiO₂ under Various Atmospheres

In this report, the photocatalytic activity of P25 has been explored and the influence of thermal treatment under various atmospheres (air, vacuum and hydrogen) were discussed. The samples’ characteristics were disclosed by means of various instruments including X-ray diffraction (XRD), Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and UV⁻vis. This study also accentuates various states of the oxygen vacancy density formed inside the samples as well as the colour turning observed in treated P25 under various atmospheres. Produced coloured TiO2 samples were then exploited for their photocatalytic capability concerning photodegradation of methylene blue (MB) using air mass (AM) 1.5 G solar light irradiation. Our findings revealed that exceptional photocatalytic activity of P25 is related to the thermal treatment. Neither oxygen vacancy formation nor photocatalytic activity enhancement was observed in the air-treated sample. H2-treated samples have shown better photoactivity which even could be further improved by optimizing treatment conditions to achieve the advantages of the positive role of oxygen vacancy (O-vacancy at higher concentration than optimum acts as electron trapping sites). The chemical structure and stability of the samples were also studied. There was no sign of deteriorating of O2-vacancies inside the samples after 6 months. High stability of thermal treated samples in terms of both long and short-term time intervals is another significant feature of the produced photocatalyst