Disposal of sewage sludge (SS) is one of the problems in treatment plants; however, SS has a high-water volume and lacks some compounds and can be mixed with other biomass. The present study analyzed co-hydrothermal carbonization of sewage sludge with sawdust and corn stalk. This research aimed to optimize the process parameters, the temperature in the range of 180–300 °C, the reaction time in the range of 30–60 min, and pH in the range of 5–9 on the mass yield, energy yield, and high heat value (HHV) to increase the quality of hydrochar, and to analyze the effect of hydrothermal carbonization (HTC) on the characteristics of raw materials and hydrochar. The response surface method and Benken’s box model were conducted using Design Expert 10 software. The optimal conditions for HHV, mass yield, and energy yield were 15.802 MJ/kg, 63.754%, and 67.415% respectively which occurred in the 205.358 °C, 30 min reaction time, and pH of 5. The temperature was the most influential parameter. The morphological, physicochemical, thermal, and crystalline properties of the hydrochar with the maximum HHV, mass yield and energy yield were evaluated as well. These results demonstrate that HTC is a suitable process to produce hydrochar, which can be used as a direct solid fuel. Highlights • Hydrothermal carbonization of sewage sludge with sawdust and cornstalk was investigated. • Response surface optimization hydrothermal carbonization process was studied. • The morphological, physicochemical, thermal, and crystalline properties of the hydrochar are reported. • The optimal HHV was 15.802 MJ/kg. • The process can produce hydrochar which can be used for direct combustion or activated carbon. Graphical abstract
Desalination of seawater is a promising response to solve the lack of drinkable water. The separation of cations and anions is carried out by inserting a desalination cell in the middle of a novel design of Photo Electro Catalytic Desalination Cell (PEDC). Different parameters were evaluated and optimized for increasing the capability of system to desalt hyper saline water. Ultraviolet illumination (UV) is used as the driving force, exciting coated titanium nanotubes on the anode electrode, producing electron/hole pairs that degrade organic matters. Methylene blue degradation by UV irradiation is undertaken, owning a high salt concentration level, and desalinated to produce electrical current. Performance of PEDCs are investigated by salt content, pH, and ion exchange resin. The results indicates that higher Total Disolved Solid (TDS) removal occurs in acidic environments in anode chamber while the maximum produced electrical current occurs in alkaline environments in cathode chamber. Also, the higher amount of salt content in the middle chamber results in the high TDS removal until the amount of Electrical Conductivity in the middle chamber is 190 mS/cm. The TDS removal rate with and without using resins in the middle of the desalination cell after 10 days is 70.69% and 51.37%, respectively.
A laboratory investigation into crude oil contaminated sand-concrete interface behavior is performed. The interface tests were carried out through a direct shear apparatus. Pure sand and sand-bentonite mixture with different crude oil contents and three concrete surfaces of different textures (smooth, semi-rough, and rough) were examined. The experimental results showed that the concrete surface texture is an effective factor in soil-concrete interface shear strength. The interface shear strength of the rough concrete surface was found higher than smooth and semi-rough concrete surfaces. In addition to the texture, the normal stress and the crude oil content also play important roles in interface shear strength. Moreover, the friction angle decreases with increasing crude oil content due to increase of oil concentration in soil and it increases with increasing interface roughness.
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