Papers by Keyword: Monolith

Abstract: Clay minerals possess substantial potential for developing innovative functional materials, particularly in the context of environmental protection. This study focuses on the adsorbent zeolite-clay and bentonite-clay, shaped into honeycomb monoliths to efficiently remove Fe²⁺ ions from water. The process involved physically activating powdered zeolite-clay and bentonite-clay through calcination at 600°C. The activated materials were then mixed with distilled water and molded into monolithic shapes through extrusion with stainless steel molds, resulting in cylindrical structures measuring 1.8 cm in diameter and 2 cm in height, featuring 40 perforations. Mechanical characterization aimed to evaluate structural strength and assess pressure drop during operation, revealing superior mechanical strength in bentonite-clay compared to zeolite-clay. The monolithic form exhibited lower pressure drop during operation compared to pellet adsorbents. In terms of adsorption performance, a batch reactor assessed efficiency, isotherm, and kinetics with 2 and 4 ppm Fe2+ ion solutions over a 240-minute period. The zeolite-clay monolith demonstrated the highest capacity, achieving a removal efficiency of up to 65%. Maximal adsorption capacities for bentonite-clay and zeolite-clay were 0.209 and 0.289 mg/g, respectively, with corresponding Langmuir adsorption equilibrium constants (KL) of 0.187 and 0.181 L/g by the Langmuir isotherm model. Kinetic analysis favored the pseudo-first-order non-linear model, indicating rates for zeolite-clay and bentonite-clay adsorbents at 2 and 4 ppm Fe²⁺ ion concentrations of 0.0043, 0.0030, 0.0039, and 0.0038 min^-1. This study signifies a significant advancement in solid adsorbents, optimizing the adsorption process for broader applications.

Abstract: Stainless steel reinforcement in the form of prestressing wires and ropes, commonly used to reinforce prestressed concrete structures [1], is also used for suspension strips of footbridge bridges. After the accident of some of them, these structures became the subject of an examination of their current state and analyses of the origin and development of corrosion of the prestressing reinforcement used. The issue of the service life of prestressed structures is related, among other things, to their structural arrangement and the construction procedure used. As with most existing prestressed structures, the anti-corrosion protection of the reinforcement has traditionally been ensured primarily by the alkalinity of the environment, ie by concreting or grouting prestressed elements in the pipeline [2].

Abstract: In this study, iron removal was carried out by the adsorption process as a well-known method of removing heavy metal. Natural bentonite with magnetic properties in a monolithic form or Magnetite-Bentonite-based Monolith (MBM) adsorbent was used as an adsorbent to remove Iron (II) ion from the aqueous solution. The magnetic properties of adsorbents are obtained by adding magnetite (Fe₃O₄), which is synthesized by the coprecipitation process. The characterization of magnetic properties was performed using the Vibrating Sample Magnetometer (VSM). VSM results showed that the magnetic particles were ferromagnetic. Adsorption efficiency, isotherm model, and adsorption kinetics were investigated in a batch system with iron solution concentration varied from 2 to 10 mg/L and magnetite loading at 2% and 5% w/w. The highest removal efficiency obtained reached 89% with a 5% magnetite loading. The best fit to the data was obtained with the Langmuir isotherm (non-linear) with maximum monolayer adsorption capacity (Q_o) at 5% magnetic loading MBM adsorbent is 0.203 mg/g with Langmuir constants K_L and a_L are 2.055 L/g and 10.122 L/mg respectively. The pseudo-first-order (non-linear) kinetic model provides the best correlation of the experimental data with the rate of adsorption (k₁) with magnetite loading 2% and 5%, respectively are 0.024 min^-1 and 0.022 min^-1.

Abstract: The removal of mercury from the waterbody remains a severe challenge in ensuring environmental safety due to its highly toxic and non-biodegradable properties. Adsorption is an evidently effective method for heavy metal removal in water. This research aims to study the mercury (II) ion adsorption behavior in aqueous solution onto extruded natural bentonite in monolithic structure, bentonite-based monolith (BBM) adsorbent. BBM was characterized by XRD, BET, and SEM, the results verify BBM could improve adsorption performance assumed on its structure. Adsorption efficiency, isotherm model, and adsorption kinetic were investigated. Experiments were performed in a lab-scale batch reactor with mercury solution concentration varied from 1 to 5 mg/L. The maximum adsorption efficiency discovered to be 63,9%. The experimental data fitted well to Langmuir isotherm (non-linear) and kinetic model pseudo first order (non-linear), revealing the maximum monolayer capacity (Q_o) of BBM to be 0,187 mg/g with Langmuir constants K_L and a_L are 0,215 L/g dan 1,151 L/mg respectively. These value confirms that BBM adsorbent encompasses tremendous potential for mercury (II) ion removal in a solution.

Abstract: The preparation conditions to obtain cobalt-nickel monolithic catalyst with high loading and homogeneous distribution are studied. Washcoating of raw monolith with gamma alumina solution was examined and characterized by SEM. A uniform layer of alumina washcoat as a support for active phase was achieved in this process. Also the effect of the molarity of solution and the number of impregnation were studied to obtain different loading of active phase on monolith walls. Catalysts with 38.81, 20.44 and 3.22 wt.% of loading were obtained by four steps of impregnation in active phase solution with 3.33, 1.42, 0.3 of molarity, respectively. It was found that increase in concentration of active phase loading leads to increase in active phase loading but reduces the uniformity of active phase distribution.

Abstract: An effective approach to synthesize methacrylate-based hybrid monoliths was carried out by photopolymerization and the properties of the obtained monoliths mixed with mult-wall carbon nanotube (MWNT) were studied in this paper. The prepared hybrid materials with MWNT in the range of 0-5% total weight of monomers were characterized by Fourier transform infrared spectra, thermo-gravimetric analysis (TGA), and mercury intrusion porosimetry, respectively. Moreover, their porosities were evaluated by the determination of flow rate for different prepared monolithic capillaries. The results showed that the monoliths with more MWNT (1-5%) possessed larger pore sizes between 1-10 μm. The hybrid monoliths have the potential advantages including stronger hydrophobic properties and less resistance for the application of reversed phase liquid chromatography in the micro-column separation.

Abstract: Spiropyran photochromic compounds can be switched using light exposure between a non-polar spiro form (SP) and a zwitterionic merocyanine form (MC) that is subject to protonation (MC-H+). It has recently been demonstrated by Walsh et al. that, under acidic conditions, electroosmotic flow (EOF) generated in vinyl based spiropyran monoliths can be modulated using light irradiation [1]. In this paper, we report a spiropyran-modified acrylate based monolith which is particularly sensitive to protonation in the MC form, producing a positively charged surface that converts to the unpolar SP form by exposure to white light. When the MC-H+ form is dominant, it produces a charged surface which enables a relatively high flow rate (up to 1.6 μl/min) to be generated under electroosmotic conditions. Upon exposure to white light, the concentration of MC-H+ decreases due to the photo-conversion to the uncharged SP form, with up to 20% reduction of the EOF. The process is reversible, and removal of the light source results in a flow increase back to the original rate. The ability to alter flow rates in micro-fluidic channels using light has very significant implications, as it could dramatically simplify the manner in which micro-flow systems are controlled.