Nitrogen-enriched activated carbon derived from plant biomasses: a review on reaction mechanism and applications in wastewater treatment

As a key kind of evolving carbonaceous adsorbent, nitrogen-enriched activated carbon has drawn a lot of focus due to its better physiochemical ability to eliminate an extensive range of wastewaters contaminants under severe conditions. Its environment-friendly character is one more reason behind this focus. Nitrogen also has immense effect on activated carbon structures’ pollutants adsorption capability; therefore, it is an area of interest. Reports concerning the reaction pathway of C-N (carbon-nitrogen) bond creation on AC surface are limited. Determining such mechanisms is challenging but critical to understand bond characteristics after carbonization. Moreover, it is vital to ascertain real-time kinetics concerning adsorption phenomena in liquid phase. Such a latest trend indicates that regulated nitrogen uses for carbonaceous substances having a biomass-based origin can provide the desired morphological characteristics produced through interconnections, production of enclosed holes, enhanced surface area, better adsorption ability, and many other benefits in contrast to conventional carbon-based substances. This review points out the developments in the main processes to introduce nitrogen atoms into the carbon matrix by utilizing different N-comprising chemical compounds. The nitrogen enrichment processes, reaction mechanisms and effects of nitrogen incorporation on the plant biomass-derived activated carbons (NEACs) are presented in brief. On the basis of their established physicochemical attributes, the adsorption performances of different biomass-derived NEACs have also been dealt with. More significantly, the review covers the technical issues in the present phase, topical trends, research gaps, economic viability along with a technical alignment recommendation to address the prevailing disadvantages

Advances in Mathematical Modeling of Gas-Phase Olefin Polymerization

Mathematical modeling of olefin polymerization processes has advanced significantly, driven by factors such as the need for higher-quality end products and more environmentally-friendly processes. The modeling studies have had a wide scope, from reactant and catalyst characterization and polymer synthesis to model validation with plant data. This article reviews mathematical models developed for olefin polymerization processes. Coordination and free-radical mechanisms occurring in different types of reactors, such as fluidized bed reactor (FBR), horizontal-stirred-bed reactor (HSBR), vertical-stirred-bed reactor (VSBR), and tubular reactor are reviewed. A guideline for the development of mathematical models of gas-phase olefin polymerization processes is presented

Polypropylene production in a fluidised BED catalytic reactor: Comprehensive modeling, optimisation and pilot scale experimental validation / Mohammad Jakir Hossain Khan

There is wide range of applications in chemical processes and energy generation in the experimental and numerical studies of multiphase flows. General uses include fluidised bed catalytic polymerization, fluidised bed reactors (type of chemical reactors), process parameters optimization, such as temperature, system pressure, monomer concentration, catalyst feed rate, superficial fluid velocity and vital technology breakthrough in various polyolefin based engineering. Via the use of Computational Fluid Dynamics (CFD) methods combined with mathematical and statistical model, this thesis concentrated on the investigation of bubble and emulsion phase dynamic transitions on polypropylene production rate. The use of ANNOVA (Analysis of variance) method with Response Surface Methodology (RSM) was used to statistically model the experiments to validate and identify the process parameters for polypropylene production was conducted by. Reaction temperature, system pressure and hydrogen percentage were the three important process variables and important input factors in the performed analysis of polypropylene production. Through the evaluation of the effects of the process parameters and their interactions, statistical analysis indicated that the proposed quadratic model had a good fit with the experimental results. The highest polypropylene production of 5.82% per pass was obtained at an optimum condition with temperature of 75 °C, system pressure of 25 bar and hydrogen percentage of 2%. With the combination of statistical model and CFD (computational fluid dynamic) method, a hybrid model was developed to explain the detailed phenomena of the process parameters. A series of experiments were also conducted for propylene polymerisation by changing the feed gas composition, reaction initiation temperature and system pressure in a fluidised bed catalytic reactor. During reaction, 75% monomer concentration (MC) was shown as the optimum propylene concentration. The multiphasic reaction models tested in this research supposed that polymerisation happened at both in the emulsion and the bubble phase. With respect to the experimental range of the superficial gas velocity and the catalyst feed rate, it was observed that the ratio of the polymer created during the bubble phase, as compared to the overall rate of production, was approximately in the range of 9.1-10.8%. This was a noteworthy quality and should not be looked over. Two different solvers were used to achieve fluid flow computation. One of them was ANSYS FLUENT which was a general-purpose CFD code expanded from UDF (user defined functions) method on a collocated grid. The expanded UDF had various physical models that could be used in a wide range of industries. The other solver was Design Expert which was developed for the optimization of a broad range of process parameters. Multiphasic model was a general-purpose hydrodynamic model that validated chemical reactions and dynamic profiles of gas-solid flow in real reaction situations that usually occurred in olefin polymerization and chemical processing reactors. It was observed that the enhanced hybrid and multiphasic models were able to forecast more constricted and safer windows at analogous conditions as compared to the experimental results. Conversely, the enhanced models had similar dynamic behaviour as the conventional model during the initial stages of the polymerisation but deviated as time progressed. Characterizations studies were conducted on the polypropylene and resulted in detailed information on the effects of the different process parameters on the product

Immobilization of activated carbon on fungal biomass used as bioadsordent for decolorization

Cost effectiveness, availability and adsorptive properties are the main criteria for choosing the bioadsorbent to remove organic compounds from wastewater. Considering these criteria, an active bioadsorbent was prepared by immobilizing the commercial activated carbon with the fungal biomass through the fermentation process. The potential strains were selected based on immobilization capability through the screening test of different types of fungi. It was observed that the strains Aspergillus niger and Penicillium were able to immobilize 100% activated carbon with its biomass. The immobilized activated carbons on biomass (IACBs) as an active bioadsorbent were characterized by elemental analysis, surface techniques SEM and FT-IR. The functional groups of the bioadsorbent were observed by Fourier transformer infrared spectroscopy (FT-IR). The surface morphology of the bioadsorbent was observed using scanning electron microscopy (SEM). From the characterization study it was observed that significant changes were occurred in surface and structure. The preliminary study on the adsorption of dyes showed significant removal of color in aqueous solution compared to the pure activated carbon. The study shows that the new IACB material might be suitable for the removal of heavy metals or toxic dyes from the industrial wastewater

Multiphasic Reaction Modeling for Polypropylene Production in a Pilot-Scale Catalytic Reactor

In this study, a novel multiphasic model for the calculation of the polypropylene production in a complicated hydrodynamic and the physiochemical environments has been formulated, confirmed and validated. This is a first research attempt that describes the development of the dual-phasic phenomena, the impact of the optimal process conditions on the production rate of polypropylene and the fluidized bed dynamic details which could be concurrently obtained after solving the model coupled with the CFD (computational fluid dynamics) model, the basic mathematical model and the moment equations. Furthermore, we have established the quantitative relationship between the operational condition and the dynamic gas–solid behavior in actual reaction environments. Our results state that the proposed model could be applied for generalizing the production rate of the polymer from a chemical procedure to pilot-scale chemical reaction engineering. However, it was assumed that the solids present in the bubble phase and the reactant gas present in the emulsion phase improved the multiphasic model, thus taking into account that the polymerization took place mutually in the emulsion besides the bubble phase. It was observed that with respect to the experimental extent of the superficial gas velocity and the Ziegler-Natta feed rate, the ratio of the polymer produced as compared to the overall rate of production was approximately in the range of 9%–11%. This is a significant amount and it should not be ignored. We also carried out the simulation studies for comparing the data of the CFD-dependent dual-phasic model, the emulsion phase model, the dynamic bubble model and the experimental results. It was noted that the improved dual-phasic model and the CFD model were able to predict more constricted and safer windows at similar conditions as compared to the experimental results. Our work is unique, as the integrated developed model is able to offer clearer ideas related to the dynamic bed parameters for the separate phases and is also capable of computing the chemical reaction rate for every phase in the reaction. Our improved mutiphasic model revealed similar dynamic behaviour as the conventional model in the initial stages of the polymerization reaction; however, it diverged as time progressed

Development of an Effective Biosorbent by Fungal Immobilization Technique for Removal of Dyes

Charcoal activated carbon was modified through immobilization techniques on fungal biomass. Two fungal strains i.e. Aspergillus niger and Penicillium sp. were selected to immobilize the charcoal activated carbon on fungal biomass. The percentage of biomass production onto activated carbon was 88% for A. niger while it was 75% for Penicillum sp. The results of scanning electron microscope (SEM) showed clear changes between the external surfaces of charcoal activated carbon (AC) and activated carbon immobilized biomass (ACIB) which also indicated the formation of matrix onto AC by fungal mycelia. The ACIBs showed more functional groups as compared to the AC. The functional groups determined by the Fourier transform infrared spectroscopy (FTIR) for the ACIBs by A. niger and Penicillium sp. indicated various changes in achieving additional functional groups (phosphate ester, cyclic ether, alcoholic and phenolic groups) as compared to the AC. The results revealed that AC was morphologically modified by the immobilization techniques. Maximum adsorption capacity by ACIB of A. niger was achieved at a dosage of 15 mg/L for Reactive Black (98.2%), Congo Red (84.6%) and Malachite Green (82.6%) while 20 mg/L dosage was required for Methylene Blue to achieve highest decolorization (92.3%). The results of individual effect of ACIB, AC and biomass on the removal of reactive black 5 showed that maximum removal was obtained at 98.2, 88 and 75% respectively. The modified biosorbents as ACIBs developed by the A. niger and Penicillium sp. in an immobilized culturing process could be a potential agent for decolorization and removal of pollutants

Advances in Mathematical Modeling of Gas-Phase Olefin Polymerization

Mathematical modeling of olefin polymerization processes has advanced significantly, driven by factors such as the need for higher-quality end products and more environmentally-friendly processes. The modeling studies have had a wide scope, from reactant and catalyst characterization and polymer synthesis to model validation with plant data. This article reviews mathematical models developed for olefin polymerization processes. Coordination and free-radical mechanisms occurring in different types of reactors, such as fluidized bed reactor (FBR), horizontal-stirred-bed reactor (HSBR), vertical-stirred-bed reactor (VSBR), and tubular reactor are reviewed. A guideline for the development of mathematical models of gas-phase olefin polymerization processes is presented

CFD simulation of fluidized bed reactors for polyolefin production - a review

This literature survey focuses on the application of computational fluid dynamics (CFD) in various aspects of the fluidized bed reactor. Although fluidized bed reactors are used in various industrial applications, this first-of-its-kind review highlights the use of CFD on polyolefin production. It is shown that CFD has been utilized for the following mechanisms of polymerization: governing of bubble formation, electrostatic charge effect, gas-solid flow behavior, particle distribution, solid-gas circulation pattern, bed expansion consequence, mixing and segregation, agglomeration and shear forces. Heat and mass transfer in the reactor modeling using CFD principles has also been taken under consideration. A number of softwares are available to interpret the data of the CFD simulation but only few softwares possess the analytical capability to interpret the complex flow behavior of fluidization. In this review, the popular softwares with their framework and application have been discussed. The advantages and feasibility of applying CFD to olefin polymerization in fluidized beds were deliberated and the prospect of future CFD applications was also discussed