Zaheer Aslam

In this study, polysulfone (PSF)-based composite membranes were synthesised through phase inversion. These membranes were then dip-coated with non-functionalized and functionalized Graphitic Carbon Nitride (g-C ₃ N ₄ ) to enhance Chromium (Cr(VI)) removal from a Cr(VI)-containing aqueous industrial water matrix. The effect of nanofiller loading and functionalization concentration on membrane morphology, thermal stability, hydrophilicity, porosity, pure water flux, and Cr(VI) rejection was systematically investigated. Thermogravimetric Analysis (TGA) depicted improved thermal stability upon incorporation of non-functionalized and functionalized g-C ₃ N ₄ , while Scanning Electron Microscopy (SEM) revealed structural modifications. Water Contact Angle (WCA) measurements demonstrated significant enhancement in surface hydrophilicity after g-C ₃ N ₄ incorporation and further improvement upon its functionalization with Para-Phenylenediamine (PPD). Among the non-functionalized membranes, the membrane containing 0.2 g g-C ₃ N ₄ exhibited optimal performance in terms of permeability and rejection. Functionalization of 0.2 g g-C ₃ N ₄ with 0.054 mg PPD resulted in the highest porosity, maximum pure water flux of 56.12 L m ⁻² h ⁻¹ and superior Cr(VI) rejection of 95.69%. The results demonstrate that moderate non-functionalized and functionalized g-C ₃ N ₄ loading significantly enhanced the membrane permeability–selectivity balance, making the optimized membrane highly suitable for Cr(VI) removal from aqueous industrial water matrices.

In this study, the cationic surfactant hexadecyl trimethylammonium bromide (HDTMA) was loaded onto coal fly ash and subsequently utilized for wastewater treatment. The surfactant-treated ash was characterized to investigate its porosity, surface morphology, thermal stability, and the presence of surface functional groups. Experimental studies were conducted under varying solution pH, adsorbent dosage, temperature, time, and initial pollutant concentration to obtain data for isothermal, kinetic, and thermodynamic analysis. The equilibrium uptake capacities of chlorobenzene (CB) and nitrobenzene (NB) using HDTMA-modified coal fly ash (HCFA) were found to be 214 mg g–1 and 74 mg g–1, respectively. Kinetic analysis revealed that the pseudo-second-order model accurately described the adsorption kinetics for both benzene derivatives, while isotherm model investigations demonstrated multilayer adsorption on the HCFA surface. The isotherm data of CB and NB conformed to the Koble Corrigan and Khan Isotherm models, respectively. Thermodynamics parameters such as ΔG° (Gibbs free energy), ΔH° (enthalpy), ΔS° (entropy) and ∆Hx (isosteric heat of adsorption) were also evaluated. The results indicated that the adsorption of chlorobenzene was exothermic, spontaneous, and feasible, whereas nitrobenzene exhibited endothermic behavior and followed the non-spontaneous process. Furthermore, variations in ∆Hx values indicated the heterogeneous nature of HCFA. Overall, the prepared adsorbent demonstrated good affinity for benzene derivatives and could be considered for the treatment of wastewater containing these pollutants.

Coal fired power plants are significant contributors to CO₂ emissions and produce solid waste in the form of coal fly ash, posing severe environmental challenges. This study explores the application of dry-impregnated coal fly ash for CO₂ capture from gas stream. The modification of coal fly ash was achieved using alkaline earth metal oxides, specifically CaO and MgO, to alter its physical and chemical properties. Characterization techniques like X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and BET (Brunauer–Emmett–Teller) analysis were employed for physio-chemical changes in the adsorbent. Breakthrough experiments were conducted using a laboratory-scale fixed packed-bed reactor to assess the influence of temperature and gas flow rate on CO₂ adsorption. Among the synthesized sorbents, calcium oxide-impregnated ash showed the highest CO₂ uptake capacity, achieving 9.41 mg/g at 30 °C and a flow rate of 20 L/hr under atmospheric pressure. Isotherm modeling indicated a heterogeneous adsorbent surface, with the data best fitting the Sips isotherm model. Furthermore, the adsorption data conformed well to the Yoon-Nelson and Thomas kinetic models, affirming their relevance in characterizing the adsorption process under varying conditions. This research emphasizes the potential of coal fly ash—an abundant, cost-free material—as an effective CO₂ adsorbent, contributing to both CO₂ mitigation and landfill waste reduction.

Sulfur dioxide is serious ultimatum to human health as well as environment, while carbon dioxide is viewed as one of the primary drivers of the worldwide temperature alteration. Therefore, capturing of these gases is a dynamic research subject attracting much consideration from scientists. Herein, we report synthesis of a series of Co‐ZIF and bimetallic M‐Co‐ZIF adsorbents and application for room temperature adsorption of SO₂ and CO₂. In this work, the breakthrough curves for the adsorption of sulfur dioxide and carbon dioxide on Co‐ZIF and M‐Co‐ZIF were obtained experimentally and theoretically using a laboratory‐scale fixed bed column at room temperature. In this work, the adsorption capacities and breakthrough points for modified bimetallic M‐Co‐ZIF were found to be relatively higher than parent Co‐ZIF. Notably, a high SO₂ uptake capacity of 7.1 mmol/g for Zr‐Co‐ZIF and high CO₂ uptake capacity of 69.9 mmol/g for Ni‐Co‐ZIF were achieved. The parent cobalt and bimetallic ZIF materials were characterized by XRD, FTIR, SEM, and nitrogen physisorption. The XRD results confirm the formation of pure phase highly crystalline ZIF materials while BET analysis suggests high surface area of prepared adsorbents. Finally, the results of dynamic adsorption combined with characterization show great potential for preparation of bimetallic ZIF adsorbents for effective SO₂ and CO₂ adsorption.

In this research study, waste fly ash (WFA) underwent acid activation and subsequent amine functionalization using ammonia solution. This treatment improves the porosity, thermal tendency and crystallinity of WFA. Modified WFA was tested under different experimental conditions to treat the wastewater consisting of different concentrations of cationic (methylene blue and rhodamine 6G) and anionic (methyl orange) dyes. As an individual, methylene blue (MB) and rhodamine 6G (Rh) showed ~ 100% and ~ 82% removal efficiencies respectively in an alkaline medium while methyl orange (MO) exhibited only ~ 20% adsorption in the same medium. An antagonistic effect was observed in adsorption when wastewater contains both cationic dyes whereas the combination of cationic and anionic dyes in solution manifested a synergistic effect. For all individual and binary dye combinations, there is a close agreement in observed and calculated uptakes when the data was fitted to the fractional order kinetic rate equation. The adsorption of all dyes is spontaneous and endothermic in nature except for MB/MO combination where the process is exothermic in nature. 24.93 mg/g, 24.83 mg/g, and 14.95 mg/g monolayer uptake capacities of MB, Rh, and MO were found respectively from isothermal analysis of single dye adsorption data. Further, extended sips model gave higher correlation coefficient (R² = 0.99) and addressed the failed assumptions of both the Langmuir and Freundlich models. Overall, in the experimental results, the modified waste fly ash could act as successful adsorbent to treat dye bearing wastewater.

Transformers are the most important component of the power system. Failure in the transformer can cause a big financial loss, so a timely inspection of the transformer is necessary. The service life of a transformer can be determined from the condition of the insulating oil by estimating carbonyl and aromaticity indices. In this research, the condition of insulating oil was evaluated through a rapid, non-destructive technique using Fourier Transform Infrared (FTIR) and ultraviolet and visible (UV-Vis) spectroscopies. The aging of the oil was performed in the presence of an insulating paper in an oven at 130°C for different residence time (48–192h), and the oil was examined using FTIR and UV-Vis after every 48h. The carbonyl and aromaticity indices were calculated from the area under the curves in FTIR at a specific wavenumber range between 1700–1600 cm^− 1 which reflects the deterioration of the insulating oil. Further, the UV-Vis spectrum intensity between 200–400 nm was used to qualitatively analyze the quality of the insulating oil. Therefore, it can be concluded that these non-destructive techniques are rapid, inexpensive, and also carry a lot of information as compared to the traditional method which can help in deciding the state of the oil.

WFA modification was done by its reaction with the mixture of ammonia solution and phosphoric acid. BET analysis of modified WFA elucidate pore volume and surface area of 0.017cm³/g, 11.1m²/g respectively. Thermo-Gravimetric Analysis (TGA) confirmed the 45% loss in weight for the WFA whereas, for modified WFA, the loss was about 12%. XRD results proposed the improved crystallinity of the modified WFA. Moreover, the zeta-potential of -40mV indicates the favorable removal efficiency, against the pH value of 6.41. Regression results from the comparison of order-based kinetic models suggest that nth model parameters justify the complex nature of the adsorption mechanism with its feasible correlation coefficient (R² > 0.95) and its lower error values for both single and binary solutions. Monolayer coverage capacities for a single solution system of Methylene Blue (MB), Rhodamine-6G (Rh) and Methyl Orange (MO) were 24.93mg/g, 24.83mg/g and 14.95mg/g respectively. Further, the isothermal model’s results suggest that the “Extended Sips” model gives relatively higher R²= 0.99 values and deals with the failed assumptions of both the Langmuir and Freundlich models. The thermodynamic model generated results conclude that involved single and binary physisorption processes were spontaneous and endothermic in the case of cation dyes solution and for MB/MO mixture it was exothermic.

A surfactant-modified coal fly ash was developed as a multifunctional adsorbent for the removal of organic pollutants from wastewater. Sodium dodecyl sulfate (SDS) was used to modify the surface of coal fly ash (CFA). The modified CFA was characterized using scanning electron microscopy (SEM), surface porosity analyzer, thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The results showed that loading CFA with SDS not only improved the functionality and surface morphology of the raw ash for the adsorption of organic pollutants, but also enhanced its thermal stability. The efficiency of the modified fly ash was tested in terms of removal of two non-polar organic pollutants namely chlorobenzene (CB) and nitrobenzene (NB) from aqueous phase. The maximum uptake capacity of chlorobenzene and nitrobenzene with SDS-modified coal fly ash (SCFA) was 225 mg/g and 90 mg/g, respectively. The kinetic analysis was done by controlled kinetic models, i.e., pseudo first and second order kinetic models. The results showed that adsorption of CB and NB onto SCFA followed a pseudo second order kinetic model. The adsorption of chlorobenzene was exothermic over the modified adsorbent while nitrobenzene showed an endothermic behavior. The isotherm analysis depicted the multilayer adsorption of both pollutants onto the surface of the surfactant modified adsorbent. This work has shown that surface modification using surfactants can be a viable option to enhance the adsorption capacity of fly ash for pollutants removal.

In this work, we investigated the photocatalytic degradation of p‐nitrophenol using a cobalt (Co)‐doped ZnO photocatalyst. The Co‐doped ZnO photocatalyst was first prepared through a simple wet impregnation method and subsequently characterized using various qualitative and quantitative techniques. Response surface methodology (RSM) was employed for experimental design and optimization of photocatalytic process. The effects including initial concentration of 4‐ Nitrophenol [4‐NP]_in, catalyst dosage, pH and irradiation time were investigated, and RSM suggested a second‐degree polynomial model for abatement of p‐nitrophenol from aqueous phase. Under optimized conditions (pH = 5; Irradiation time = 180 min; catalyst dosage = 30 mg; [4‐NP]_in = 30 mg/L), up to 82% degradation was achieved, signifying the efficacy of the prepared photocatalyst. Moreover, the real case study was employed by incorporating Co‐doped ZnO nanocomposite for treatment of real paper wastewater and results showed a considerable photocatalytic activity of Co–ZnO nanocomposites on paper wastewater.