Conversion of waste polystyrene into valuable aromatic hydrocarbons via microwave-assisted pyrolysis.

The prime objective of the current research work was to understand the role of microwave-assisted pyrolysis for the upgradation of expanded polystyrene (EPS) waste into valuable aromatic hydrocarbons. Ethyl acetate solvent was used to dissolve the EPS to enhance the homogeneous dispersion of EPS with susceptor particles. Biochar obtained from the pyrolysis was used as a susceptor. The design of experiments method was used to understand the role of microwave power (300 W, 450 W, and 600 W) and susceptor quantity (5 g, 10 g, and 15 g) in the pyrolysis process. The pyrolysis was conducted till the temperature reached up to 600 °C, and this temperature was achieved in the time interval of 14-38 min based on the experimental conditions. The obtained average heating rates varied in the range of 15 to 41 °C/min to attain the pyrolysis temperature. The EPS feed was converted into char (~ 2.5 wt.%), oil (51 to 60 wt.%), and gaseous (37 to 47 wt.%) products. The specific microwave energy (J/g) was calculated to know the energy requirement; it increased with an increase in susceptor quantity and microwave power, whereas specific microwave power (W/g) was a function of microwave power and increased from 15 to 30 W/g. The predicted values calculated using the model equations closely matched the actual values showing that the developed model equations via optimization had a good fit. The obtained pyrolysis oil physicochemical properties including viscosity (1 to 1.4 cP), density (990 to 1030 kg/m3), heating value (39 to 42 MJ/kg), and flash point (98 to 101 °C) were thoroughly analyzed. The pyrolysis oil was rich in aromatic hydrocarbons and it was predominantly composed of styrene, cyclopropyl methylbenzene, and alkylbenzene derivates.

A novel tri-metal adsorbent used for defluoridation technique from groundwater: performance and mechanism.

In this research article, a novel adsorbent (Zn-Fe-Al) was synthesized successfully by a simple chemical route where three oxides combined to enhance affinity towards fluoride. The physicochemical properties of the adsorbent were used to characterize and assess its effectiveness in defluoridation with both synthetic and groundwater. The TEM results demonstrated the overlapping of metals, and EDX shows the metals present in the adsorbent. The maximum defluoridation efficiency (97%) of Zn-Fe-Al was obtained at an optimized initial pH 7 and adsorbent dose 0.08 g L-1. The fluoride adsorption on Zn-Fe-Al followed the D-R isotherm and intraparticle diffusion. The maximum adsorption capacity of Zn-Fe-Al was found to be 187 mg g-1. The adsorption of fluoride on Zn-Fe-Al was found to be endothermic and spontaneous. The Zn-Fe-Al adsorbent exhibited satisfactory defluoridation performance on real groundwater. The co-existing ions were also investigated. The adsorption mechanisms for fluoride were electrostatic interaction and ion exchange. These results demonstrated that Zn-Fe-Al adsorbent was considered high potential for effective defluoridation of groundwater.

Synthesis of sustainable chemicals from waste tea powder and Polystyrene via Microwave-Assisted in-situ catalytic Co-Pyrolysis: Analysis of pyrolysis using experimental and modeling approaches.

In the current study, catalytic co-pyrolysis was performed on waste tea powder (WTP) and polystyrene (PS) wastes to convert them into value-added products using KOH catalyst. The feed mixture influenced the heating rates (17-75 °C/min) and product formation. PS promoted the formation of oil and WTP enhanced the char formation. The maximum oil yield (80 wt%) was obtained at 15 g:5 g, and the maximum char yield (44 wt%) was achieved at 5 g:25 g (PS:WTP). The pyrolysis index (PI) increased with the increase in feedstock quantity. High PI was noticed at 25 g:5 g, and low PI was at 5 g:5 g (PS:WTP). Low energy consumption and low pyrolysis time enhanced the PI value. Significant interactions were noticed during co-pyrolysis. The obtained bio-oil was analyzed using GC-MS and a plausible reaction mechanism is presented. Catalyst and co-pyrolysis synergy promoted the formation of aliphatic and aromatic hydrocarbons by reducing the oxygenated products.

Enrichment in CO2 Absorption by 2-Methyl Piperazine-Activated Tertiary Amines, Physical Solvents, and Ionic Liquid Systems.

One of the ever-demanding research fields is the development of new solvents with better properties for mitigation of CO2 compared to existing solvents. This work reports the measurement and modeling of CO2 solubility in newly proposed aqueous solvent blends of 2-methyl piperazine with N-methyldiethanolamine (MDEA), sulfolane (TMSO2), and 1-butyl-3-methyl-imidazolium acetate ([bmim] [Ac]). The operating temperature and CO2 partial pressure conditions chosen were 303.2-323.2 K and 2-370 kPa, respectively. Along with this, qualitative 13C NMR and FTIR analysis were also performed to consider the proposed reaction scheme. The experimental vapor-liquid equilibrium data were modeled by a modified Kent-Eisenberg equilibrium model. The equilibrium constants associated with 2-methyl piperazine (2-MPZ) and [bmim] [Ac] deprotonation and carbamate formation reactions were regressed to fit the experimental CO2 solubility data. In addition, the CO2 cyclic capacity and heat of absorption were evaluated for the aq (MDEA + 2-MPZ) blend.

Effectiveness of ionic liquid-supported membranes for carbon dioxide capture: a review.

The world's population explosion creates a need for natural resources for energy, which will become a significant contributor to global climate change. As we all know, carbon dioxide (CO2) is one of the most critical elements of the global greenhouse gas effect. CO2 capture and storage innovations have piqued researchers' attention in recent decades. Compared to other methods, membrane separation has some positive performance in CO2 capture. CO2 capture with membrane separation using enhanced ionic liquids (ILs) is described in this review. ILs have made an appearance in CO2 capture work as the potential additive, and companies and academics have been interested in CO2 separation for the past two decades. This article comprehensively analyzes the current modern approach in ILs and IL-based membranes for gas separation processes. Based on the latest literature and performance data, this work provides a complete compressive examination of types of ILs and IL-supported membrane performances. ILs for CO2 capture were also explored, and IL-based membranes for different ILs were also studied. This study emphasizes the supremacy of novel ILs for CO2 capture in membrane separation.

Trihexyl tetradecyl phosphonium bromide as an effective catalyst/extractant in ultrasound-assisted extractive/oxidative desulfurization.

Phosphonium-based ionic liquid (PIL) has been used as a catalyst and extractant. Here, the PIL, trihexyl tetradecyl phosphonium bromide ([THTDP]Br) was utilized for the S-removal of model oil (MO) and acted as the reaction-induced self-separation catalyst. The influence of oxidant to sulfur molar ratio (n(O/S)), mass ratio of model oil to ionic liquid (m(MO/IL)), sonication time, and temperature was observed to investigate the optimal conditions for the ultrasound-assisted extractive/oxidative desulfurization (UEODS) catalyzed by [THTDP]Br. A kinetic study was performed, and the reaction rate constant and half-life were calculated as the oxidation reaction was following pseudo-first-order reaction kinetics. Moreover, the oxidation reactivity and selectivity of various sulfur substrates were in the following order: DBT > BT > TH > 3-MT. The DBT removal with various initial S-content was observed to be constant, which makes it feasible for practical application. The interaction energy between [THTDP]Br and S-compounds was examined using Density Functional Theory. The sulfur removal of base oil (BO) was also examined using various desulfurization systems at DBT optimized conditions. The highest desulfurization efficiency of BO was obtained during the UEODS process, which made it industrially feasible. [THTDP]Br was regenerated and recycled six times with a slight variation in efficiency.

Prospects of titanium carbide-based MXene in heavy metal ion and radionuclide adsorption for wastewater remediation: A review.

Contamination of water sources with various organic and inorganic non-biodegradable pollutants is becoming a growing concern due to industrialization, urbanization, and the inefficiency of traditional wastewater treatment processes. Transition Metal Carbides/Nitrides (MXenes) are emerging as advanced nanomaterials of choice for treating contaminated water owing to their excellent conductivity, mechanical flexibility, high specific surface area, scalable production, rich surface functionalities, and layered morphology. MXenes have demonstrated enhanced ability to adsorb various organic and inorganic contaminants depending upon their surface terminal groups (-OH, -F, and -O) and interlayer spacing. Titanium carbide (Ti3C2Tx) is most researched to date due to its ease of processing and stability. Ti3C2Tx has shown excellent performance in absorbing heavy metal ions and radioactive heavy metals. This review summarizes state-of-the-art Ti3C2Tx synthesis, including selective etching techniques, optimization of the desired adsorption features (controlling surface functional groups, intercalation, sonication, and functionalization), and regeneration and adsorption mechanism to remove contaminants. Furthermore, the review also compares the adsorption performance of Ti3C2Tx with other commercial adsorbents (including chitosan, cellulose, biomass, and zeolites). Ti3C2Tx has been found to have an adsorption efficiency of more than 90% in most studies due to its layered structure, which makes the functional groups easily accessible, unique and novel compared to other conventional nanomaterials and adsorbents. The challenges, potential solutions, and prospects associated with the commercial development of Ti3C2Tx as adsorbents are also discussed. The review establishes a framework for future wastewater treatment research using MXenes to address the global problem of water scarcity.

CO2 reduction routes to value-added oxygenates: a review.

Energy is a key attribute that is used to evaluate the economic development of any country. The demand for energy is going to rise in developing countries and will be 67% of global use by 2040. The energy surge in these rising economies will be responsible for 60-70% of the global greenhouse gas emissions. The quest for higher energy motivates technological development to curb the climate change occurring with GHG emissions. Carbon dioxide is one of the primary greenhouse gases in the atmosphere. Current work is intended to give an updated review on the different routes of carbon dioxide utilization that are catalytic route, photocatalytic route, electrocatalytic route, microwave plasma route, and biocatalytic route. These routes are capable of converting CO2 into different valuable products such as formic acid, methanol, and di-methyl ether (DME), which are majorly derived from biomass and/or fossil fuels (coal gasification and/or natural gas). This work investigates the effect of different routes available for the production of value-added products by CO2 reduction, discusses various challenges that come across the aforementioned routes, and shares views on future scope and research direction to pave new innovative ways of reducing CO2 from the environment.

Optimization of fluoride removal by Al doped ZnO nanoparticles using response surface methodology from groundwater.

The current novel work presents the optimization of factors affecting defluoridation by Al doped ZnO nanoparticles using response surface methodology (RSM). Al doped ZnO nanoparticles were synthesized by the sol-gel method and validated by FTIR, XRD, TEM/EDS, TGA, BET, and particle size analysis. Moreover, a central composite design (CCD) was developed for the experimental study to know the interaction between Al doped ZnO adsorbent dosage, initial concentration of fluoride, and contact time on fluoride removal efficiency (response) and optimization of the process. Analysis of variance (ANOVA) was achieved to discover the importance of the individual and the effect of variables on the response. The model predicted that the response significantly correlated with the experimental response (R2 = 0.97). Among the factors, the effect of adsorbent dose and contact time was considered to have more influence on the response than the concentration. The optimized process parameters by RSM presented the adsorbent dosage: 0.005 g, initial concentration of fluoride: 1.5 g/L, and contact time: 5 min, respectively. Kinetic, isotherm, and thermodynamic studies were also investigated. The co-existing ions were also studied. These results demonstrated that Al doped ZnO could be a promising adsorbent for effective defluoridation for water.

Triphenyl methyl phosphonium tosylate as an efficient phase transfer catalyst for ultrasound-assisted oxidative desulfurization of liquid fuel.

The novel phosphonium-based ionic liquid (IL), triphenyl methyl phosphonium tosylate ([TPMP][Tos]), has been synthesized and applied as a phase transfer catalyst (PTC) in the ultrasound-assisted oxidative desulfurization (UAODS). Oxidation of model fuel (MF) containing dibenzothiophene (DBT) was carried out using an equimolar mixture of H2O2-CH3COOH as an oxidant at 40-70 °C in the presence of IL. The sulfur compound is converted into polar sulfone, and the maximum desulfurization efficiency was examined. The effect of process parameters such as reaction temperature, reaction time, molar ratio of oxidant to sulfur (n(O/S)), and the mass ratio of ionic liquid to model fuel (m(IL/MF)) was studied, and the conditions for maximizing the DBT conversion rate were found. Maximum conversion (> 99%) was obtained at a temperature of 70 °C with m(IL/MF) of 0.8. The oxidation reactivity of various sulfur compounds was studied at different time intervals. To verify the effect of ionic liquid and ultrasound irradiation, extractive desulfurization (EDS), oxidative desulfurization (ODS), and UAODS in the presence of IL were carried out. The experimental results show that the UAODS process gives the highest desulfurization efficiency. A kinetic study was performed to estimate the rate constant and the order of oxidation reaction.

Synthesis, characterization, and application of iron oxyhydroxide coated with rice husk for fluoride removal from aqueous media.

A novel nanoparticle (NPs) iron oxyhydroxide modified with rice husk (RH + FeOOH) was synthesized with wet chemical method. Batch study was performed to investigate fluoride removal and adsorption capacity. The RH + FeOOH NPs were characterized by using Fourier transform infrared spectroscopy, X-ray powder diffraction, Brunauer-Emmett-Teller, scanning electron microscope with energy dispersion, transmission electron microscope, and particle size analyzer. By varying parameters, batch adsorption with adsorption capacity was performed such as contact time, stirring rate, adsorbent dosage, temperature, initial concentration, and pH. The BET surface area and the pore volume of the FeOOH and RH + FeOOH were found to be 157 m2 g-1, 195 m2 g-1 and 0.136 m2 g-1, 0.224 m2 g-1. Based on kinetic study, pseudo-second-order was followed by regression coefficient (R2) 0.99. Langmuir isotherm model showed the best adsorption capacity of 26 mg g-1. Moreover, the RH + FeOOH showed best affinity towards fluoride removal and may act as an excellent adsorbent for fluoride treatment from aqueous solution. Synthesis and Fluoride Adsorption Mechanism of Iron Oxyhydroxide Modified with rice husk.

Thermally induced characterization and modeling of physicochemical, acoustic, rheological, and thermodynamic properties of novel blends of (HEF + AEP) and (HEF + AMP) for CO2/H2S absorption.

CO2 and H2S removal from flue gases is indispensable to be done for protection of environment with respect to global warming as well as clean air. Chemical absorption is one of the most developed and capable techniques for the removal of these sour gases. Among the many solvents, ionic liquids (ILs) are more capable due to their desirable green solvent properties. However, ILs being usually costlier, the blends of ILs and amines are more suggestive for absorption. In the present work, various essential characterization properties such as density, viscosity, sound velocity, and refractive index of two ionic liquid-amine blend systems viz. (1) 2-Hydroxy ethyl ammonium formate (HEF) + 1-(2-aminoethyl) piperazine (AEP) and (2) 2-Hydroxy ethyl ammonium formate (HEF) + 2-Amino-2-methyl-1-propanol (AMP) are reported. The temperature range for which all the measurements were conducted is 298.15 to 333.15 K. For both systems of (HEF + AEP) and (HEF + AMP), HEF mass fractions were varied from 0.2 to 0.8.The density and viscosity results were correlated as a function of temperature and concentration of ionic liquid and amine with Redlich-Kister and Grunberg-Nissan models, respectively. Moreover, feed forward neural network model (ANN) is explored for correlating experimentally determined sound velocity and refractive index data. The measured properties are further analyzed to estimate various thermodynamic as well as transport properties such as diffusivity of CO2/H2S in the (HEF + AEP) and (HEF + AMP), thermal expansion coefficients, and isentropic compressibility, ΔG0, ΔS0, ΔH0, using the available models in the literature.

Sulfur extraction from liquid fuels using trihexyl(tetradecyl)phosphonium tetrafluoroborate: as promising solvent.

Sulfur extraction from fuel is essential to be done for environmental and industrial point of view. Extractive desulfurization (EDS) is one of the most promising techniques in order to achieve legislative sulfur content requirements. Among numerous extractants and solvents, ionic liquids (ILs) are more capable due to their desirable green solvent properties. This work demonstrated that trihexyl(tetradecyl)phosphonium tetrafluoroborate ([THTDP]BF4) was synthesized, characterized, and employed as extraction solvent for extraction of dibenzothiophene (DBT), thiophene, benzothiophene, and other alkyl-substituted derivatives of sulfur from liquid fuel. Molecular confirmation and purity of synthesized ([THTDP]BF4) were analyzed with FTIR, Raman, NMR, EPR, UV, TG/DSC, and XRD analyses. Also, physical properties of ([THTDP]BF4) were carried out. The effects of extraction time, temperature, sulfur compounds, ultra-sonication, and ([THTDP]BF4) recycling/regeneration on DBT removal from liquid fuel were also examined. DBT removal in n-dodecane was 92.6% using EDS with mass ratio (1:1) in 30 min at 30 °C under the mild reaction conditions. ([THTDP]BF4) could be reused up to ten cycles for sulfur extraction and regenerated for few more cycles with good DBT removal ability. Also, the sulfur extraction from real fuels and multistage extraction performance were tested. The experimental data and results provided in this article discover the remarkable understandings of tetrafluoroborate-based phosphonium ionic liquids as promising solvent for EDS.

Synthesis, characterization, and application of 1-butyl-3-methylimidazolium thiocyanate for extractive desulfurization of liquid fuel.

1-Butyl-3-methylimidazolium thiocyanate [BMIM]SCN has been presented on extractive desulfurization of liquid fuel. The FTIR, (1)H-NMR, and C-NMR have been discussed for the molecular confirmation of synthesized [BMIM]SCN. Further, thermal, conductivity, moisture content, viscosity, and solubility analyses of [BMIM]SCN were carried out. The effects of time, temperature, sulfur compounds, ultrasonication, and recycling of [BMIM]SCN on removal of dibenzothiophene from liquid fuel were also investigated. In extractive desulfurization, removal of dibenzothiophene in n-dodecane was 86.5 % for mass ratio of 1:1 in 30 min at 30 °C under the mild process conditions. [BMIM]SCN could be reused five times without a significant decrease in activity. Also, in the desulfurization of real fuels, multistage extraction was examined. The data and results provided in the present paper explore the significant insights of imidazolium-based ionic liquids as novel extractant for extractive desulfurization of liquid fuels.

Synthesis, characterization and application of 1-butyl-3 methylimidazolium chloride as green material for extractive desulfurization of liquid fuel.

The possible application of imidazolium ionic liquids as energy-efficient green material for extractive deep desulfurization of liquid fuel has been investigated. 1-Butyl-3-methylimidazolium chloride [BMIM]Cl was synthesized by nucleophilic substitution reaction of n-methylimidazolium and 1-chlorobutane. Molecular structures of the ILs were confirmed by FTIR, (1)H-NMR, and (13)C-NMR. The thermal properties, conductivity, solubility, water content and viscosity analysis of [BMIM]Cl were carried out. The effects of reaction time, reaction temperature, sulfur compounds, and recycling of IL without regeneration on dibenzothiophene removal of liquid fuel were presented. In the extractive desulfurization process, the removal of dibenzothiophene in n-dodecane using [BMIM]Cl was 81% with mass ratio of 1 : 1, in 30 min at 30°C under the mild reaction conditions. Also, desulfurization of real fuels with IL and multistage extraction were studied. The results of this work might offer significant insights in the perceptive use of imidazoled ILs as energy-efficient green material for extractive deep desulfurization of liquid fuels as it can be reused without regeneration with considerable extraction efficiency.