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In the present study, the adsorption behavior of ciprofloxacin (CIP) from aqueous solution onto MWCNTs/Al2O3 was studied using batch experiments. Physical characterization of MWCNTs/Al2O3 was determined by SEM, XRD, and BET. The effective parameters investigated included: initial CIP concentration, contact time, MWCNTs/Al2O3 mass, and temperature. Based on experimental results and correlation coefficients, the rate of CIP adsorption followed the pseudo-second-model kinetics. Complete compatibility of the adsorption isotherm process was achieved with the Langmuir model, and the maximum adsorption capacity reached 41.73 mg/g under the optimized conditions (pH = 7, MWCNTs/Al2O3 dose = 1.2 g/L, contact time = 60 min, initial concentration = 10 mg/L, and temperature= 45 °C). The adsorption capacities based on the Langmuir model at different temperatures, 273, 288, 303, and 318 K, were equal to 72.18, 75.92, 79.65, and 83.47 mg/g, respectively. The determined parameters of the thermodynamic studies demonstrated the endothermic and spontaneous nature of the biosorption. The mean free energy was estimated from D–R isotherm model to be 0.316–0.707 KJ/mol, which clearly proved that the adsorption experiment followed a physical process. The data suggest that MWCNTs/Al2O3 could be used as a highly effective adsorbent material with a high capacity for the removal of antibiotics from water and wastewater. [ABSTRACT FROM AUTHOR]

Pyrolysis has gained significant attention due to its generation of value-added products from waste feeds in an environmentally friendly manner. The primary purpose of this study is to understand the effect of different particle sizes of biomass wastes – date stones (DS), cow manure (CM), and spent coffee grounds (SCG) – to understand better and design a biomass pyrolysis system. Thermogravimetric analysis of four different sizes of DS, SCG, and CM (range 1 mm to 125 μm) and a mixed sample (for each feed) was conducted at a heating rate of 10K/min from room temperature to 1173.15 K at inert conditions and employed model-based Coats–Redfern equations to understand the kinetic and thermodynamic parameters of the pyrolysis process. All the particle sizes except 355–125 μm for DS and SCG have the best-fit reaction mechanism of Ginstling-Brounshtein (D4). Both activation energy and pre-exponential factor decreased from 18.78 to 5.57 kJ/mol and 1.16 E+10 to 1.48 E+08 with reducing particle sizes. The onset degradation temperature, activation energy, change in enthalpy, and entropy decrease with particle sizes. The product formation is favored for all feeds and particle sizes, as the difference between the enthalpy and activation energies (Ea) is below 10 kJ/mol. As a result of their substantially lower activation energies and better reaction thermodynamics, mixed and smaller particle-sized biomass are favored. [ABSTRACT FROM AUTHOR]

Global waste production is significantly rising with the increase in population. Efforts are being made to utilize waste in meaningful ways and increase its economic value. This research makes one such effort by utilizing gas-to-liquid (GTL)-derived biosolids, a significant waste produced from the wastewater treatment process. To understand the surface properties, the biosolid waste (BS) that is activated directly using potassium carbonate, labelled as KBS, has been characterized using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), and Brunauer–Emmett–Teller (BET). The characterization shows that the surface area of BS increased from 0.010 to 156 m2/g upon activation. The EDS and XPS results show an increase in the metal content after activation (especially iron); additionally, XRD revealed the presence of magnetite and potassium iron oxide upon activation. Furthermore, the magnetic field was recorded to be 0.1 mT using a tesla meter. The magnetic properties present in the activated carbon show potential for pollutant removal. Adsorption studies of methylene blue using KBS show a maximum adsorption capacity of 59.27 mg/g; the adsorption process is rapid and reaches equilibrium after 9 h. Modelling using seven different isotherm and kinetic models reveals the best fit for the Langmuir-Freundlich and Diffusion-chemisorptionmodels, respectively. Additional thermodynamic calculations conclude the adsorption system to be exothermic, spontaneous, and favoring physisorption. [ABSTRACT FROM AUTHOR]

Waste management is an increasing global concern due to the rise in urbanization and industrialization. This study examines the co-pyrolysis of date pits (DP) and single-use plastics (polypropylene-PP and Styrofoam-PS) as a way to create value-added products. Single, binary, and ternary mixtures were pyrolyzed at three different heating rates to understand the synergy, kinetics, and thermodynamics. The results showed positive synergy and reduced activation energies during co-pyrolysis, due to varying reaction mechanisms. The positive values of ∆H, ∆G, and negative ΔS indicate endothermic non-spontaneous reactions and disorder in the products instead of the reactants during pyrolysis. Future studies should explore upscaling this process for sustainable energy production. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption of a large reactive dye, Reactive Black 5, onto four adsorbents has been studied. A commercial active carbon, F400, was selected as a standard and two active carbons prepared from bamboo, a biomaterial. The two bamboo derived carbons, BACX2 and BACX6 had high specific surface areas, namely, 2123 and 1400m2/g, respectively. A fourth widely used adsorbent, bone char, was also tested. The adsorption capacities for F400, bone char, BACX2 and BACX6 were 198, 160, 286 and 473mg/g, respectively. A series of batch kinetics were carried out to investigate the rate and possible mechanism of Reactive Black 5 adsorption. Two pseudo-kinetic models and one intraparticle diffusion model were tested. The experimental concentration versus time decay curves were best explained by the intraparticle diffusion model. [Copyright &y& Elsevier]

This research demonstrates the capability of carbon nanotubes (CNT) modified with four generations of poly-amidoamine dendrimer (PAMAM, G4) to remove Cu 2+ and Pb 2+ heavy metals from aqueous solution in single and binary component systems. Uniquely high adsorption capacities for copper and lead, which are 3333 and 4870 mg/g respectively, were achieved. FTIR, H 1 NMR, Zeta potential, SEM and TEM techniques were employed for characterizing the synthetic nanocomposite and indicated that the dendrimer functionalized CNTs have been synthesized. The effects of several parameters including initial metal ion concentration, solution pH and the nanocomposite dosage were studied. The experimental data were analyzed by the Langmuir and Freundlich isotherms and the pseudo-first order and pseudo-second order kinetics models. The maximum adsorption occurred at pH = 7. The adsorption process for Cu 2+ and Pb 2+ in single and binary component systems fit the Langmuir and extended Langmuir models respectively. This study also tested the kinetic sorption of the metals on PAMAM/CNT in single and binary component metal systems at various metal ions concentrations. The results showed that PAMAM/CNT nanocomposite was a super-adsorbent, able to uptake uniquely large quantities of heavy metal from single and binary component liquid phase. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a feasible and cost effective method to produce amine functionalized multi-walled carbon nanotubes (CNT-NH 2 ) and investigate the ability of this CNT-NH 2 material to adsorb anionic dyes in single and binary (mixture of dyes) systems. For this purpose, pristine CNTs were functionalized by primary and secondary functional groups namely (-NH2) and (-NH), respectively. Acid Blue 45 (AB45) and Acid Black 1 (AB1) were used as anionic dye models for adsorption. FTIR, SEM, BET, Raman Spectra, and Zeta potential measurements have been employed for characterizing the synthetic nanocomposite and these techniques indicated that the amino functionalized CNTs have been favorably synthesized. The effects of different operational parameters including pH, initial dye concentration, adsorbent dosage, and salt on dye removal were evaluated. The dye adsorption isotherm and kinetics were also studied. The results of this study indicated that the stronger interactions between CNT-NH 2 and AB1 suggest a higher adsorption of AB45 compared to AB1 in both single and binary dye systems. Moreover, the maximum adsorption capacities of the studied functionalized nanotube in single dye solutions, for AB45 and AB1 were 714 and 666 mg g −1 , respectively. These capacities are exceptionally high for the removal of acid dyes. It was found that AB45 and AB1 adsorption on the CNT-NH 2 followed the Langmuir isotherm model and pseudo-second order kinetics model in both single and binary systems. According to the results of this study the CNT-NH 2 were an effective adsorbent to remove anionic dyes from single and binary systems. [ABSTRACT FROM AUTHOR]

The water cleaning applications of carbon nanotubes (CNT) have generated much research interest since their initial discovery. However, in the early stages of research, the efficiency of CNTs for the removal of heavy metal ions has been severely limited because of the intense agglomeration of CNTs and their deficiency of functional groups. In this research, a new method has been discovered for the preparation of dendrimer functionalized CNTs and a PAMAM/CNT nanocomposite was prepared. FTIR, SEM, TEM, Raman spectroscopy, zeta potential measurements, and dispersion observing methods have been employed for characterizing the synthetic nanocomposite and these techniques indicated that the dendrimer functionalized CNTs have been favorably synthesized. In addition, the uniquely high adsorption capacities properties of PAMAM/CNT nanocomposite for Ni 2 + , Zn 2 + , As 3 + , Co 2 + were examined. The effects of several parameters including initial metal ion concentration, temperature, solution pH, the nanocomposite dosage and contact time were studied. The experimental data were analyzed using equilibrium isotherm relationships (Langmuir, Temkin and Freundlich) and the uniquely high adsorption capacities and rates were studied using (pseudo-first order, intraparticle diffusion and pseudo second-order) adsorption kinetics models. The results indicated that the maximum adsorption occurred at pH = 8. With increasing nanocomposite dosage and increasing contact time, there was increased adsorption capacity. Analysis of the adsorption process demonstrated that the Langmuir isotherm and pseudo-second order kinetics are the most appropriate models for heavy metal ions adsorption onto PAMAM/CNT nanocomposite. [ABSTRACT FROM AUTHOR]

Sunflower oil methanolysis over CaO - based palm kernel shell biochar (PKSB) catalyst was assessed by coupling full factorial design with modeling, optimization and kinetic studies. According to the analysis of variance, the effect of reaction temperature and methanol-to-oil molar ratio on the fatty acid methyl ester (FAME) synthesis is significant, while the effect of catalyst loading is statistically negligible. The optimum reaction conditions are found to be catalyst loading of 3 wt%, temperature of 65 °C and methanol-to-oil molar ratio of 9:1, ensuring the best FAME content of 99%. The kinetic model of the methanolysis of sunflower oil, catalyzed by PKSB-based catalyst, combines the changing- and first-order reaction rate laws with respect to triacylglycerols and FAMEs, respectively. The high activation energy (108.8 kJ/mol) indicates the temperature sensitivity of the reaction. The CaO-based PKSB catalyst can be reused without any treatment in three consecutive cycles with no significant drop in activity. Since the calcium content in the biodiesel product is higher than the standard limit, the overall process should include a purification stage. [ABSTRACT FROM AUTHOR]

In this work, rice husk cellulosic sorbents are produced by both chemical and biological pretreatment. The results indicate that the sorbent pretreated by sodium hydroxide (NaOH) and hydrogen peroxide (H 2 O 2 ) contains up to 87.75% cellulosic concentration. Acetylated sorbents produced from both NaOH/H 2 O 2 and Aspergillus flavus pretreated rice husks are compared with raw rice husk and non-acetylated rice husk sorbents for oil sorption capacities. By plotting oil uptake capacity against contact time, the optimum theoretical sorption capacity of acetylated chemical pretreated rice husk sorbent is 28.2 g/g RMG 386 after 15 min dripping. The sorption data shows that the modified rice husk sorbents achieve saturation after only 3–5 min of contact with both RMG 386 marine diesel and corn oil. The experimental data of acetylated chemical pretreated rice husk sorbent is analyzed using the pseudo-first order, the pseudo-second order and the intraparticle diffusion models. The model results indicate that the pseudo-second order model accurately correlates with the oil sorption data. In terms of the equilibrium isotherm analysis, the Freundlich model provides the best fit to the experimental data. As a result, the acetylated rice husk sorbent has shown to significantly outperform the non-acetylated sorbent with a high oleophilic and hydrophobic capacity with up to 19.66 g/g RMG 386 oil uptake capacity compared to 8.26 g/g by the non-acetylated rice husk sample in an aqueous medium. [ABSTRACT FROM AUTHOR]

Abstract: The sorption of arsenate onto chitosan flakes has been studied. Chitosan, a natural, non-toxic, biodegradable polysaccharide is derived by the deacetylation of chitin, a major component of crustacean shells of prawn, crab or shrimp. Its main attributes correspond to its polycationic nature and the abundance of amine functional groups. Chitosans have received increasing attention as renewable polymeric materials for the treatment of metal contaminated water and wastewater. The effect of initial pH on the sorption isotherm has been studied for two initial concentration ranges of arsenate (0–3000μgL−1 and 0–10,000μgL−1) on chitosan. The equilibrium data have been modelled using Langmuir and Freundlich type isotherms at three initial pH values. The maximum adsorption capacity occurs at an initial pH 3.5 and empirical correlations have been developed to model the effect of pH on the sorption isotherm parameters. Each initial pH i value, namely, 3.5, 4.0 and 4.5, corresponded to a fixed final pH e value, namely, 4.69, 6.40 and 6.73 respectively. A series of batch kinetic experiments has been carried out at different initial pH values. The arsenate sorption process appears to be completed after 30min, however, a previously unreported phenomenon was observed, namely, a steady desorption of arsenate. There is a natural buffering effect from the chitosan. The batch kinetic data have been correlated using the pseudo-first order, pseudo-second order and pseudo-first order reversible models; this latter model was modified to incorporate the arsenate desorption step as a function of the changing system pH. [Copyright &y& Elsevier]

Abstract: The ability of a new ion exchange resin to remove zinc ions from effluent has been studied. The equilibrium exchange capacity has been determined as 2.7mmol/g resin and analysed using the Langmuir, Freundlich and Redlich–Peterson equations. The Redlich–Peterson gave the best-fit to the experimental data. A series of kinetic studies were carried out in an agitated batch reactor. Three variables were studied, initial zinc ion concentration, resin mass and resin particle size. The results were analysed using three kinetic models, pseudo-first order, pseudo-second order and the Elovich model. The results were compared on the basis of SSE values and the best-fit correlation of the experimental data was obtained using the Elovich model which suggests a chemisorption process. [Copyright &y& Elsevier]

• A review on sources and composition of sewage sludge for pyrolysis. • Thermal degradation studies and behavior of sewage sludge using TGA. • Review of mechanism and principles of pyrolysis process for sewage sludge. • Comprehensive discussion on the selection of kinetic models for scale up. • Application of machine learning tool forprediction of kinetic data. Sewage sludge is a by-product of the wastewater treatment process, which has the potential to be a source of transport fuels, heat, and power using the pyrolysis process. Considering the prevalence and disposal issues associated with sewage sludge, the objective of this study is to critically review the recent advancements in sewage sludge pyrolysis and its kinetics obtained using the thermogravimetric techniques, and other associated different kinetic models documented in the literature. The study will identify optimum operating conditions and design parameters to obtain high yields. The state-of-the-art perspectives and the challenges associated with full-scale implementation are highlighted for biofuels and resource recovery from the sewage sludge. Furthermore, machine-learning approaches in thermal kinetics of pyrolysis are presented and discussed in terms of their effectiveness in predicting thermal kinetics data. Finally, the challenges for a successful implementation and commercial viability of sewage sludge pyrolysis are discussed. [ABSTRACT FROM AUTHOR]