Sanghamitra Barman

EXPERIMENTAL INVESTIGATION ON ADSORPTION OF AMIDO BLACK 10B DYE ONTO ZEOLITE SYNTHESIZED FROM FLY ASH

ABSTRACT This work presents experimental studies on adsorptive removal of Amido black 10B dye using a low-cost zeolite synthesized from fly ash to study the effect of various parameters, namely pH, temperature, agitation speed, adsorption time, zeolite loading, and dye concentration, on dye removal efficiency. Dye removal efficiency increased with increase in adsorbent dosage, adsorption time, and stirrer speed, and the optimal values of zeolite dose, adsorption time, and stirrer speed were found to be 10 g/L, 6 h, and 300 rpm respectively. On the other hand, dye removal efficiency decreased with increase in the initial dye concentration as well as temperature, indicating that the adsorption process is exothermic and is effective at low concentrations of adsorbate. Maximum dye removal was obtained at low pH values (between 2 and 5), indicating the fact that the zeolite surface is positively charged. Experimental data matched well with the pseudo-first-order kinetic model and the Freundlich equilibrium isotherm. The most important observation in this work is that zeolite synthesized from fly ash could act as a very effective adsorbent for the removal of amido black dye from its aqueous solutions.

Surface Modification of Synthesized Nanozeolite NaX with TEAOH for Removal of Bisphenol A

In the present study, the surface modification of a freshly synthesized nanozeolite NaX was done with tetraethylammonium hydroxide (TEAOH) and applied as an adsorbent for the removal of bisphenol A (BPA) from its aqueous solutions. The adsorbent was characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the synthesized adsorbent can remove BPA rapidly and effectively because of its high surface area (572 m2/g) and small particle size (35 nm). Uptake of BPA was greatly influenced by pH, stirring rate, temperature, contact time, and adsorbent dose. The optimum values of these parameters were 10.5 pH, 250 rpm, 25°C, 2 h, and 0.6 g/L. The adsorption was found to be spontaneous and exothermic. The Freundlich isotherm model and pseudo-first-order kinetic model fitted the experimental results well. The monolayer and multilayer adsorption capacities were found to be 42.8 and 122.6 mg/g, respectively.

Removal of emerging contaminants daidzein and coumestrol from water by nanozeolite beta modified with tetrasubstituted ammonium cation

In present research, a simplistic hydrothermal method was adopted for one-step synthesis of nanozeolite beta (NZB) having an average particle size of 18nm with Si/Al ratio 46.67, surface area 328m2/g, pore volume 0.287cm3/g, and pore diameter 3.5nm. The surface of the synthesized NZB was modified with 0.5wt% hexadecyltrimethylammonium bromide (HDTMA-Br) and used as an adsorbent for the removal of two phytoestrogens daidzein and coumestrol from aqueous solutions. The surface properties and surface charge of NZB considerably changed after modification with HDTMA-Br, which resulted in enhanced removal of daidzein (92-98% from 7 to 27%) and coumestrol (93.5-99% from 5 to 9.2%). The surface modified zeolite beta (SMZB) has similar physical characteristics as of NZB with an average particle size of 20nm, surface area 299.8m2/g, pore volume 0.263cm3/g, and pore diameter 3.51nm. The influence of various parameters was examined by conducting a sequence of batch experiments. The adsorption equilibrium was achieved in less than 3h with saturation capacity of 40.74mg/g and 42.87mg/g for daidzein and coumestrol, respectively. The Freundlich isotherm and fractional order kinetic models represented the adsorption data very closely. The thermodynamic parameters indicated that sorption of both phytoestrogens onto SMZB is spontaneous and exothermic.

Tailoring of nanozeolite NaX for enhanced removal of a phytoestrogen from its aqueous solutions

ABSTRACT This study represents the application of nanozeolite NaX (NZX) synthesized by hydrothermal treatment without addition of any expensive structure directing agent for the highly effectual adsorption of biochanin A from aqueous solution. The characteristics and surface morphology of NZX were determined using FT-IR, SEM, TEM, BET, and XRD. The adsorption performance of NZX was analyzed at different conditions such as temperature, pH, contact time, adsorbent dose, and initial adsorbate concentration. The adsorption mechanism was well verified by pseudo-second-order kinetic and Redlich–Peterson isotherm models. The thermodynamic parameters revealed that the removal process was exothermic and spontaneous.

Optimization of process parameters for transalkylation of toluene to xylene using response surface methodology

ABSTRACT H-beta zeolite was modified by the ion exchange method to replace its H+ ions with Ce4+ ions. The catalytic performance of this cerium exchanged beta zeolite was evaluated for vapor phase transalkylation of 1,2,4 TMB (1,2,4 trimethylbenzene) with toluene for the production of xylene in a fixed bed, down-flow reactor. The modified zeolite was found to be highly active for this transalkylation reaction. The response surface methodology (RSM) is used for designing the experiments. The effect of three important reaction parameters viz. temperature, reactant ratio, and space time on response variables (toluene conversion and xylene selectivity) is studied and discussed. All the three selected reaction parameters were found to be significant for the toluene conversion; whereas, xylene selectivity was not much influenced by the temperature. The optimum values of the reaction parameters predicted by the model (temperature: 409.7°C, reactant ratio: 2.024, and space time: 4.451) were validated by an experimental run. The results of the experimental run were in close agreement with the model predicted results.

Kinetic Investigation in Transalkylation of 1,2,4 Trimethylbenzene with Toluene over Rare Earth Metal-Modified Large Pore Zeolite

Gas-phase transalkylation of 1,2,4 trimethylbenzene (1,2,4-TMB) with toluene was carried out for the production of xylene in a fixed-bed reactor at 1 atm pressure over cerium-modified NaX zeolites. The modified zeolites were characterized by Energy Dispersive Spectra, X-ray Diffraction, and Scanning Electron Microscopy. The acidic properties of metal-modified zeolites were studied using the Temperature Programmed Desorption profile of ammonia. The effects of various parameters like cerium content, catalyst loading, temperature, reactant mole ratio, and space-time were investigated to select the optimum process conditions to maximize the specific product of transalkylation. NaX zeolite modified with cerium exhibited higher activity and stability than the unmodified zeolite in time-on-stream study. Maximum toluene conversion of 44.96% and xylene selectivity of 55.13% were obtained over CeX10 (X zeolite exchanged with 10% ceric ammonium nitrate solution) at 723 K, reactant mole ratio 2.5, and space-time 4.44 kg · h/kmol. Experimental data was fitted in the Langmuir–Hinshelwood–Hougen–Watson (LHHW) model based on dual-site, single-site, and stoichiometric equations. The kinetic and adsorption parameters for toluene conversion were calculated using nonlinear regression. The activation energy for this transalkylation reaction was found to be 60.3 kJ/mol.

Surface Modification of Nanocrystalline Zeolite X and Its Application as Catalyst in Synthesis of Cumene in a Packed Bed Flow Reactor: A Kinetic Study

Abstract In the present investigation, synthesis of cumene by transalkylation of 1, 4 DIPB with benzene was studied over cerium modified nano crystalline zeolite X in a fixed bed plug flow reactor. Nano crystalline zeolite X was synthesized and characterized by XRD, SEM, TPD, EDS and FTIR. A series of nanocrystalline zeolite X (MX4, MX6, MX10) modified with ceric ammonium nitrate of different concentrations (4 %, 6 %, 10 %) was used for synthesis of cumene. MX10 zeolite was proved to be the most active catalyst over which 27.12 % yield of cumene was obtained at temperature 553K, benzene/1, 4 DIPB mole ratio of 7.5 and space time-10.54 kg h/kmol. Reduction of crystal size (100–500 nm) in MX10 increases surface area (633m2/gm) and thereby increases cumene yield. A kinetic rate equation was developed from the product distribution pattern following Langmuir–Hinshelwood approach. Kinetic parameters were estimated by nonlinear regression analysis. The activation energy for transalkylation and isomerisation reaction was found to be 88.86 kJ/mol and 99.04 kJ/mol respectively.