Copper oxide (CuO) nanoparticles (NPs) were decorated on reduced graphene oxide (rGO) through the effective synthetic route method. Powder X-ray diffraction, Fourier transform infrared, ultraviolet-visible absorption, and scanning electron microscopy techniques were used to analyze the chemical structure, functional groups, absorbance, and morphology. Under visible light illumination, the CuO/rGO nanocomposites have higher catalytic activity compared to the bare CuO NPs which were suitable for degradation of methylene blue (MB) and Congo red (CR) dyes. According to the findings, the CuO/rGO nanocomposites possess excellent photocatalytic efficiency. Thus, the synthesized CuO/rGO nanocomposite is a promising photocatalyst for the deterioration of organic pollutants in water and wastewater treatment.

This research deals with the effect of the temperature on the physical, thermal, electrochemical, and adsorption properties of the carbon micro-spheres using hydrothermal carbonization (HTC). Until recently, limited research has been conducted regarding the effects of delignification during the HTC process of biomass residues especially Dimocarpus longan. In this regard, lignin was first extracted from the lingo-cellulosic waste of Longan fruit peel (Dimocarpus longan). The holocellulose (HC) separated from lignin and raw biomass substrates (Longan fruit exocarp/peel powder, LFP) were carbonized at different temperatures using water as the green catalyst. Hydrothermal carbonization (HTC) was performed for both of the samples (LFP and HC) at 200 °C, 250 °C, and 300 °C for 24 h each. The surface morphological structures, the porosity, and the Brunauer-Emmett-Teller (BET) surface area of the prepared micro-spherical carbon were determined. The BET surface areas obtained for HC-based carbon samples were lower than that of the raw LFP based carbon samples. The carbon obtained was characterized using ultimate and proximate analyses. The surface morphological features and phase transformation of the synthesized micro-spherical carbon was characterized by a field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis. The results demonstrated that the extraction of lignin could significantly alter the end properties of the synthesized carbon sample. The carbon spheres derived from LFP showed a higher carbon content than the HC-based carbon. The absence of lignin in the holo-cellulose (HC) made it easy to disintegrate in comparison to the raw, LFP-based carbon samples during the HTC process. The carbonaceous samples (LFP-300 and HC-300) prepared at 300 °C were selected and their adsorption performance for Pb (II) cations was observed using Langmuir, Freundlich, and Temkin linear isotherm models. At 30 °C, the equilibrium data followed the Langmuir isotherm model more than the Freundlich and Temkin model for both the LFP-300 sample and the HC-300 sample. The potential of the synthesized carbon microspheres were further analyzed by thermodynamic characterizations of the adsorption equilibrium system.

Solid waste management needs re-evaluating in developing countries like Pakistan, which currently employs landfilling as a first option. Over time, increasing population will result in decreasing space for landfill sites, ultimately increasing the cost of landfilling, while increasing accumulated waste will cause pollution. Locating and preparing a sanitary landfill includes the securing of large sectors and also everyday activity with the end goal to limit potential negative impacts. Energy production from municipal solid waste (MSW) is a perceptive idea for large cities, such as Karachi, as waste, which is an undesirable output that adds to land and air pollution, is transformed into a vital source of energy. The current study strives to provide a destination to solid waste by evaluating the energy potential that waste provides for power generation by the process of incineration. A sustainable energy generation plant based on the Rankine cycle is proposed. This study evaluates the various landfill sites in the case study area to determine their sustainability for a waste to energy (WtE) plant. The implementation of the proposed plant will not only provide an ultimate destination to waste but also generate 121.9 MW electricity at 25% plant efficiency. Thus, the generated electricity can be used to run a WtE plant and meet the energy requirements of the residents.

The strong electrostatic adsorption (SEA) method was applied to the synthesis of a cobalt (Co) catalyst on a multi-walled carbon nanotube (CNT) support. In order to uptake more of the cobalt cluster with higher dispersion, the CNT was functionalized via acid and thermal treatment. The Co/CNT catalyst samples were characterized by a range of methods including the Brunauer–Emmet–Teller (BET) surface area analyzer, transmission electron microscopy (TEM), X-ray powder diffraction (XRD) analysis, atomic absorption spectroscopy (AAS), and H₂-temperature programmed reduction (H₂-TPR) analysis. The data from the TEM images revealed that the catalyst was highly dispersed over the external and internal walls of the CNT and that it demonstrated a narrow particle size of 6–8 nm. In addition, the data from the H₂-TPR studies showed a lower reduction temperature (420 °C) for the pre-treated catalyst samples. Furthermore, a Fischer–Tropsch synthesis (FTS) reaction was chosen to evaluate the Co/CNT catalyst performance by using a fixed-bed microreactor at different parameters. Finally finding the optimum value of the cobalt loading percentage, particle size, and calcination conditions of Co/CNT catalyst resulted in a CO conversion and C₅₊ selectivity of 58.7% and 83.2%, respectively.

This study focuses on the extraction of cellulose nano-whiskers (CNWs) from the leaves of Adansonia kilima (AK), usually known as African baobab, using a combination of a microwave-assisted alkali (KOH) pre-treatment with subsequent bleaching process prior to ultra-sonication. Ultra-sonication was carried out using the ionic liquid (IL) 1-butyl-3-methylimidazolium hydrogen sulfate (Bmim-HSO₄). Process parameters for ultra-sonication were optimized using a two-level factorial Box–Behnken design (BBD). Process variables such as ultra-sonication power (x₁), hydrolysing time (x₂) and temperature (x₃) were varied. Responses selected were percentage crystallinity index, CrI% (y₁) and yield% (y₁) for the finally procured CNWs sample. Regression analysis was carried out to develop quadratic model to analyze the effect of process variables on IL-assisted ultra-sonication process. Analysis of variance (ANOVA) showed that ultra-sonication power was the most influential aspect for hydrolyzing the amorphous segments of crude cellulose extracted from baobab leaves. A relative study of the physio-chemical properties of the starting lignocellulosic substrate (AK), KOH pre-treated, bleached and IL-assisted ultra-sonicated CNWs was conducted. The synthesized samples were characterized using Fourier transform infrared spectroscopy, Scanning electron microscopy, atomic force microscopy, high resolution transmission electron microscopy, X-ray diffraction and thermo-gravimetric and zeta potential analysis. Under optimum condition, the extracted CNWs showed an average width of 15–20 nm; with high crystallinity index of 86.46%. This research provides an insight about the delignification of Adansonia kilima (AK) leaves and its effective conversion to CNWs having high crystallinity.

Pre-treating the multi-walled carbon nanotubes (CNTs) support by refluxing in 35 vol% nitric acid followed by heating at the temperature of 600 to 900 °C resulted in the formation of defects on the CNTs. Increasing the temperature of the pre-treatment of the CNTs from 600 °C to 900 °C, enhanced the fraction of cobalt-oxide nanoparticles encapsulated in the channels of CNTs from 31% to 70%. The performance of Co/CNTs in Fischer-Tropsch synthesis (FTS) was evaluated in a fixed-bed micro-reactor at a temperature of 240 °C and a pressure of 2.0 MPa. The highest CO conversion obtained over Co/CNTs.A.900 was 59% and it dropped by ~3% after 130 h of time-on-stream. However, maximum CO conversion using Co/CNTs.A.600 catalysts was 28% and it decreased rapidly by about 54% after 130 h of time-on-stream. These findings show that the combined acid and thermal pre-treatment of CNTs support at 900 °C has improved the stability and activity of the Co/CNTs catalyst in FTS.