Tag Archives: mesoporous silica

Our work on mesoporous silicas accepted in Microporous and Mesoporous Materials

Our work on mesoporous silicas and its applications has been accepted for publication in Microporous and Mesoporous Materials (impact factor 3.453) published by Elsevier. This journal is the official journal of International Zeolite Association. It covers novel and significant aspects of porous solids classified as either microporous (pore size up to 2 nm) or mesoporous (pore size 2 to 50 nm). The porosity should have a specific impact on the material properties or application. Typical examples are zeolites and zeolite-like materials, pillared materials, clathrasils and clathrates, carbon molecular sieves, ordered mesoporous materials, organic/inorganic porous hybrid materials, or porous metal oxides. Both natural and synthetic porous materials are within the scope of the journal.

Our accepted paper is:

PEG-templated mesoporous silicas using silicate precursor and their applications in desiccant dehumidification cooling systems

Heru Setyawan, Minta Yuwana, Ratna Balgis

HIGHLIGHTS
1. A cheap approach for producing mesoporous silica from silicate is proposed.
2. The mesoporous silicas have very high surface area which can reach > 600 m2/g.
3. The pore structure of mesoporous silicas can be tuned easily.
4. Impregnation of hygroscopic salt enhances significantly water adsorption.
5. The adsorbent composite is promising for desiccant dehumidifying cooling system.

Abstract

Polyethylene glycol (PEG) was employed as a templating agent for the preparation of mesoporous silica materials starting from sodium silicate solutions using a sol-gel method. We show that PEG can serve as a structure-directing agent resulting in silica structures with pores spanning a range of 3.3 to 3.9 nm depending on the PEG concentration and the PEG removal method. The use of a PEG template increased significantly the surface area from 252 m2 g-1 without PEG to >340 m2 g-1 and >634 m2 g-1 when the PEG was removed by, respectively, calcination and solvothermal extraction. It appears that calcination at high temperature caused a densification of the pore structure resulting in a smaller surface area and pore diameter. The impregnation of mesoporous silica with CaCl2 significantly increased the adsorption capacity of water. At high humidity, the composite adsorbents containing approximately 42 wt.% CaCl2 yield a maximum adsorption capacity of 1.6 times their own weight and 4.4 times that of bare silica. The adsorption is physical in nature as viewed from the adsorption energy calculated by the Dubinin-Radushkevich (D-R) equation.

Keywords: Mesoporous silica; Water Vapor; Sodium silicate; PEG-silica hybrid; Composite
adsorbent.

Our work on controlling pore structure of silica from bagasse ash is accepted for publication in Colloid Surf A

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Our work on controlling the pore structure of mesoporous silica from bagasse ash has been accepted for publication in the Colloids and Surfaces A: Physicochemical and Engineering Aspects (Impact Factor 2.354) published by Elsevier. This journal is an international journal devoted to the science underlying applications of colloids and interfacial phenomena. The research papers published in this journal feature new materials or new insights into the role of colloid and interface science in (for example) food, energy, minerals processing, pharmaceuticals or the environment. The title of our paper is

Synthesis of mesoporous silica with controlled pore structure from bagasse ash as a silica source

by Nanik Astuti Rahman, Ika Widhiana, Sri Rachmania Juliastuti, Heru Setyawan

HIGHLIGHTS
1. A novel and cheap approach for producing mesoporous silica is proposed.
2. The mesoporous silicas have very high surface area which can reach > 600 m2/g.
3. The pore structure of mesoporous silicas can be tuned easily.
4. Bagasse ash, a solid waste of sugar mills, is a viable material to produce mesoporous silicas.

Abstract

Mesoporous silica with controlled pore structure was prepared from bagasse ash as a silica source. The silica in the bagasse ash was dissolved by NaOH solution to produce sodium silicate precursor for the mesoporous silica, with or without polyethylene glycol (PEG) template. Without the PEG template, the pore structure was greatly influenced by the pH and the presence of Na+ ions. The porous silica produced in the presence of Na+ possessed higher surface area and pore diameter than those produced in the absence of Na+. The surface area and pore diameter reached approximately 525 m2/g and 18 nm, respectively, when the gelation pH was 3. When the gelation pH was increased, the surface area decreased while the pore diameter increased. The use of PEG template increased significantly the surface area, which reached approximately 656 m2/g when the template was removed by solvothermal extraction. Calcination at high temperature caused a densification of pore structure resulting a smaller surface area, pore diameter and pore volume. The pore diameter for all cases was greater than 4 nm, indicating that the silicas were mesoporous.

Keywords: Bagasse ash; Mesoporous silica; Sodium silicate; PEG template; Silica-PEG hybrid.

Overview of our article about mesoporous SiO2 from geothermal sludge

One more paper is accepted in Adv. Powder Technol.

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One more paper of our work is accepted for publication in Advanced Powder Technology (Impact factor: 1.510) published by Elsevier; a journal on various areas of powder and particles that include: Production of powder and particulate materials in gases and liquids (nanoparticles, fine ceramics, pharmaceuticals, novel functional materials, etc.); Aerosol and colloidal processing; Powder and particle characterization; Dynamics and phenomena; Calculation and simulation (CFD, DEM, Monte Carlo method, population balance, etc.); Measurement and control of powder processes; Particle modification; Comminution; Powder handling and operations (storage, transport, granulation, separation, fluidization, etc.).

A facile method for the production of high-surface-area mesoporous silica gels from geothermal sludge

Srie Muljani, Heru Setyawan,Gede Wibawa, Ali Altway

Highlights

High-surface area mesoporous silicas were succesfully prepared by a facile chemical method.
Two-step aging increases the surface area of silica gels and can reach 600 m² g^-1.
The silica gel properties can be tailored by changing the operating conditions.
The silica gels can be used for adsorbent, catalyst host and ultrafilters.

Abstract

Mesoporous silica gels were successfully produced from geothermal sludge by alkali extraction followed by acidification. The silica in the geothermal sludge was dissolved by NaOH solution to produce a sodium silicate solution, which was then reacted with HCl or tartaric acid to produce silica gels. The effects of silica concentration and pH on the silica gel properties were investigated. In addition, an improved method was proposed by incorporating two-step aging. The first aging step, which was conducted at pH 10, was used to induce Ostwald ripening to increase the size of the primary particles, and the second step was used to strengthen the gel network. Decreasing the silica concentration by diluting the as-prepared sodium silicate solution tended to increase the surface area and pore volume of the prepared silica gels. The silica gels produced by tartaric acid possessed higher surface area and pore volume than those by HCl.The surface area and pore volume reached approximately 450 m² g⁻¹ and 0.8 cm³ g⁻¹, respectively. When the gelation pH was decreased to 6, the surface area exceeded 600 m² g⁻¹. The first aging process increased the size and uniformity of the primary particles, which in turn increased the surface area of the particles. The pore diameter for all cases was greater than 5 nm, indicating that the silica gels were mesoporous.

Graphical Abstract