Clean Technol., Vol. 1, Pages 141-153: Optimization of Alachlor Photocatalytic Degradation with Nano-TiO2 in Water under Solar Illumination: Reaction Pathway and Mineralization In the present study, the photocatalytic degradation of alachlor was investigated using TiO2 under sunlight irradiation. The effects of some operational parameters, such as photocatalyst concentration, temperature, pH, sunlight intensity and irradiation time, were optimized. The kinetics of photodegradation was found to follow a pseudo-first-order kinetic law, and the rate constant at optimal condition is 0.245 min−1. The activation energy (Ea) is 6.4 kJ/mol. The alachlor mineralization can be completed under sunlight irradiation after 10 h. The formations of chloride, nitrate and ammonium ions are observed during the photocatalytic degradation. The eight photoproducts were identified by the GC–MS technique. The photodegradation reaction pathways are proposed based on the evidence of the detected photoproducts and the calculated frontier electron densities of the alachlor structure. The photocatalytic degradation treatment for the alachlor wastewater under solar irradiation is simple, convenient and low cost.

Clean Technol., Vol. 1, Pages 125-140: Removal of COD and Ammonia Nitrogen by a Sawdust/Bentonite-Augmented SBR Process Water pollutant removal by biomass adsorbent has been considered innovative and cost-effective, and thus commendable for application in industry. However, certain important aspects have been overlooked by researchers, namely the efficiency in the operation time and pollutant removal. In this research, landfill leachate samples with organic components were treated using a bentonite-enriched sawdust-augmented sequencing batch reactor (SBR) process. By modifying the pH, the sawdust samples were categorized into three groups: the acidic, the alkaline, and the neutral. To bentonite samples, the pH-adjusted sawdust was added at 10%, 20%, and 30% amounts by mass, respectively. At the optimum aeration rate of 7.5 L/min and contact period of 22 h, the treatment achieved 99.28% and 95.41% removal of chemical oxygen demand (COD) and NH3-N with bentonite, respectively. For both pollutants, in the presence of sawdust, the removal was only reduced by about 17% with the contact period reduced to 2 h, which was a considerable achievement.

Clean Technol., Vol. 1, Pages 114-124: Preparation and Characterization of Chemically-Modified Biomaterials and Their Application as Adsorbents of Penicillin G The prevalence of antibiotics in water creates microbial resistance and has a negative impact on the ecosystem. Biomaterials such as spent tea leaves are rich in functional groups and are suitable for chemical modification for diverse applications. This research proposes the use of spent tea leaves of chamomile (CM), green tea (GT), and peppermint (PM) as structural scaffolds for the incorporation of carboxyl, sulfonyl, and thiol groups to improve the adsorption of Penicillin G (Pe). Adsorbents characterization reported a higher number of acidic functional groups, mainly in thiolated products. Scanning electron microscopy (SEM) analysis showed changes on the surfaces of the adsorbents due to reaction conditions, with a stronger effect on thiolated and sulfonated adsorbents. Elemental analysis by Energy dispersive X-ray spectrophotometry (EDS) corroborated the chemical modification by the presence of sulfur atoms and the increase in oxygen/carbon ratios. Batch experiments at different pH shows a strong pH-dependence with a high adsorption at pH 8 for all the adsorbents. The adsorption follows the trend CMs > GTs > PMs. Thiolation and sulfonation reported higher adsorptions, which is most likely due to the sulfur bridge formation, reaching adsorption percentages of 25%. These results create a new mindset in the use of spent tea leaves and their chemical modifications for the bioremediation of antibiotics.

Clean Technol., Vol. 1, Pages 89-113: Modeling and Simulation of a Novel Combined Solar Photovoltaic-Thermal Panel and Heat Pump Hybrid System A numerical simulation model for a novel concept of a hybrid composed of photovoltaic-thermal solar panels and a heat pump is presented. This concept was developed to assess the performance and energy conversion efficiency of the hybrid system used to produce domestic hot water and electricity. A two-dimensional heat transfer and fluid flow dynamic model was developed to describe the behavior of the hybrid system under different solar irradiance, heat pump boundary conditions and different refrigerants. The model is based on dynamic mass and energy equations coupled with the heat transfer coefficients, and the thermodynamic properties of refrigerants as well as material properties. The model compared fairly to experimental data.

Clean Technol., Vol. 1, Pages 70-88: The Potential Renewable Energy for Sustainable Development in Tanzania: A Review Currently, renewable energy development is emphasized for sustainable development goals accomplishment and the better realization of sustainable development globally. Tanzania, like other developing countries, is striving to adopt different ways of ensuring affordable and accessible energy supply to its socioeconomic and political sectors to achieve renewable energy development. To secure affordable and accessible energy in the country, renewable energy is termed as an alternative energy source because of it is environmentally friendly. If renewable energy is produced and utilized in a modern and sustainable manner, it will help to eliminate energy problems in Tanzania. Thus, this study aims to review the current potential renewable energy for the achievement of sustainable development in Tanzania. Moreover, challenges of renewable energy development are examined.

Clean Technol., Vol. 1, Pages 58-69: On the Removal and Desorption of Sulfur Compounds from Model Fuels with Modified Clays The presence of sulfur compounds in fossil fuels has been an important concern in recent decades as an environmental risk due to the increase of greenhouse gases in the atmosphere and accentuation of acid rain. This study evaluates modified clays as low-cost and efficient adsorbents for the removal of dibenzothiophene (BT) and 4,6-dibenzothiophene (DBT). Adsorption was investigated in a batch system with synthetic fuels (gasoline and diesel) as a function of type of clay modification, adsorbent dosage, initial concentration of the pollutants, desorption, and isotherm modeling. Maximum adsorption was observed with clays modified with benzyltrimethylammonium ion (BM), achieving a maximum adsorption capacity (qmax) of BT of 11.3 mg/g in gasoline and 31.3 mg/g in diesel. The formation of Van der Waals interaction as well as aromatic forces as the main mechanism is proposed based on the results. A 40% desorption was accomplished in 0.1 N HCl. Adsorbents were characterized by scanning electron microscopy (SEM) and Fourier transform-infrared spectroscopy (FT-IR), indicating their optimum properties as adsorbents in fuels. This work highlights the potential use of reverse polarity clays in the elimination of sulfur compounds from model fuels as a low-cost and environmentally friendly purification technique.

Clean Technol., Vol. 1, Pages 40-57: Biogas Cleaning: Activated Carbon Regeneration for H2S Removal The coupling of fuel cell technology with wastewater treatment plants (WWTPs) is within the sustainable development imperative for the integration of energy production purposes and recovery of materials, even if research is still under development in this field. The anaerobic digestion process can be used for fuel cell feeding, only if trace contaminants are removed continuously. The most harmful and frequent contaminant is H2S. This article shows the results of H2S adsorption on activated carbon fixed-beds (dry process), since it is one of the best solutions from both the complexity and costs perspectives. Inside the wide range of commercial activated carbons, a specific commercial carbon has been used in test campaigns, since it is also used in the Società Metropolitana Acque Torino (SMAT) real plant. Thermal regeneration of spent carbons was exploited, using different conditions of temperature, treatment time and atmosphere, since it is a better cost-effective and environmentally sound option than immediate carbon disposal after adsorption. Regeneration with CO2 showed the best regeneration ratio values. In particular, the best conditions achieved were 300 °C and 75 min of thermal treatment time, with a regeneration ratio of 30%.

Clean Technol., Vol. 1, Pages 9-39: The Drivers and Barriers of Renewable Energy Applications and Development in Uganda: A Review Following the increasing global awareness of the dangers posed by the present state of climate change, many countries such as Uganda have adapted long-term plans for a transition to decarbonised economies. A major strategy for decarbonisation is to replace fossil fuels with renewable energy (RE) sources as the fundamental energy source. Uganda has substantial RE resources for the provision of energy services and production, yet these resources remain untapped. It is therefore crucial that the use of these abundant resources should be heightened. This paper examines and discusses the potential and current RE utilization and development in Uganda from the perspective of sustainable development. The status of the different RE resources and their application/utilization, including details of existing projects in the country, are carefully explored and discussed. The possible drivers for a huge advancement of RE applications and development in Uganda are also discussed before elucidating the major barriers and challenges faced by the energy sector as regards RE. Measures and policies required to facilitate the utilization of RE in Uganda are proposed. These evidence-based policies could guide the delivery of affordable and sustainable energy solutions for all by 2030 in Uganda.

Clean Technol., Vol. 1, Pages 2-8: Membrane-Assisted Condenser In industrial processes, recycling and reusing of process streams—and of water, in particular—is necessary for minimizing fresh water requirements. Water supply issues are increasing in importance for new and existing industrial plants because the freshwater supply is limited and the forecast are that by 2025 two-thirds of people will live in regions with water scarcity. In this short note, the potentialities of a membrane-assisted condenser for the recovery of evaporated waste water from industrial gases are presented. The modelling of the process was carried out for predicting the membrane-based process performance. The experimental data were compared with the results achieved through the simulations. The comparison showed good agreement confirming the validity of the realized model and its suitability for a screening of the operative conditions to be utilized.

Clean Technol., Vol. 1, Pages 1: Introduction to a New Open Access Journal by MDPI: Clean Technologies Nowadays, we are experiencing rapid economic and technological development all over the world[...]