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Applications of Biosorption in Dyes Removal
Published in Sanjay K. Sharma, Bioremediation, 2019
Jaqueline Benvenuti, Santiago Ortiz-Monsalve, Bianca Mella, Mariliz Gutterres
Four types of sorbent materials are widely used: activated carbon, zeolites, silica gel and activated alumina (Yang 2003). Commercial activated carbon is characterized by high specific surface area, physical-chemical stability and mechanical strength, high porosity and adsorption capacity, as well as the possibility of regeneration (Yahya et al. 2015). Zeolites are crystalline aluminosilicates with an orderly distribution of micropores with uniform size (pore diameter <2 nm) (Li and Yu 2014). Silica gel is an amorphous form of silicon dioxide that has high thermal and mechanical stability and several functional groups on the surface of its micropores (Wang et al. 2014). Alumina presents high specific surface area, mechanical and thermal resistance, good stability over a wide pH range and does not disintegrate when immersed in water (Abou-Ziyan et al. 2017). Activated carbon is one of the oldest adsorbents and, because of its versatility, is widely used in the removal of organic and inorganic pollutants in water and sewage treatment (Gamal et al. 2018). It is effective in removing color, odor, taste and other impurities from the water, recovering solvents and controlling air pollution (Danish and Ahmad 2018). The raw materials most used in the production of activated carbon are coconut shell, mineral coal, peat, wood among others (Lee et al. 2014).
Adsorption Cooling Heat Pumps
Published in Sotirios Karellas, Tryfon C. Roumpedakis, Nikolaos Tzouganatos, Konstantinos Braimakis, Solar Cooling Technologies, 2018
Sotirios Karellas, Tryfon C. Roumpedakis, Nikolaos Tzouganatos, Konstantinos Braimakis
Silica gels: Silica gel is one of the most popular adsorbents. Silica gels owe their wide use to their large capacity, low cost, market availability, and their ease of regeneration at approximately 150oC, in contrast to zeolites, which require 350°C (Yang 2003, Kim et al. 2017). This type of adsorbent is appropriate for low grade waste heat sources (Wu and Li 2009). Silica gel is a porous, granular form of silica with small particle size of 2–5 nm and a large surface-to-volume ratio (Shahata 2016). Silica gel is synthesized either from polymerization of Si(OH)4 or from aggregation of colloidal silica. As a water adsorbent, silica gel is characterized by average adsorptive capacity (Tso and Chao 2012). Adsorption systems with silica gel-water working pairs have been widely investigated either in single or multiple stage systems (Mitra et al. 2015; Chua et al. 2001; Thu et al. 2011).
Basic Concepts: Separation Processes and Other Unit Operations
Published in Victor H. Edwards, Suzanne Shelley, Careers in Chemical and Biomolecular Engineering, 2018
Victor H. Edwards, Suzanne Shelley
Silica gel is silicon dioxide that has been processed to form porous particles that have a very large surface area. For example, one typical silica gel has a surface area of 5 acres per ounce or 750 square meters per gram. Water is readily adsorbed on the surface of silica particles, and a monolayer of water molecules on the silica surface can give a water concentration of 30% by weight in silica.
The regeneration of various saturated solid and novel composite desiccant using Scheffler solar concentrator: an experimental investigation
Published in International Journal of Ambient Energy, 2020
Anish Malan, Vikrant Kamboj, Ashwani Kumar Sharma, Avadhesh Yadav
Outcomes of the investigation are summarised as follows: The maximum regeneration rate of 0.0518 kg/hr is achieved at the surface temperature of 105°C.Mean wind velocity, mean solar intensity, and mean surface temperature during the experimentation are 1.18 m/s, 851.76 W/m2, and 107.32°C, respectively.The maximum temperature of 168°C is achieved on the surface of silica gel when wind velocity is 0.5 m/s.The change in colour of silica gel from pink to blue is observed as an indication of complete regeneration as shown in Figure 8.It takes 160 min in complete regeneration of the silica gel under subjected conditions, and weight reduction of 22.741% has been achieved.The moisture content in silica gel is 0.2944 kg water/kgdry desiccant.
Recent advances in technologies for the removal of volatile methylsiloxanes: A case in biogas purification process
Published in Critical Reviews in Environmental Science and Technology, 2019
Gang Wang, Zhongshen Zhang, Zhengping Hao
Silica-based adsorbents, such as silica gel and zeolite, can also be used for VMS adsorption. Silica gel is a porous, inorganic polymer consisting mainly of silicon dioxide (SiO2·nH2O). Silica gel has a three-dimensional tetrahedral structure with many silanol (Si-OH) groups attached to the surface. The internal pores are interconnected, increasing the adsorption property of silica gel. Structurally, the silanol and Si-O-Si groups of silica gel are similar to VMS molecular and show strong affinity for VMS (Sigot, Ducom, Benadda, & Laboure, 2014; Sigot, Ducom, Benadda, & Laboure, 2016; Ortega & Subrenat, 2009). When waste gases containing VMS pass through the adsorbent bed, hydrogen bonds form between the surface hydroxyl groups of silica gel and VMS molecules, efficiently adsorbing siloxanes (Cabrera-Codony et al., 2014). In 2001, Schweigkofler and Niessner (2001) first identified silica gel as a promising adsorbent for siloxane removal. Subsequent studies have examined a series of silica gels with different morphologies and their adsorption properties are shown in Table 4.
The regeneration of various solid desiccants using novel heated surface plate based on heat pipe vacuum tube collector: an experimental investigation
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Rahul Srivastava, Chandrashekara M., Avadhesh Yadav
Silica gel is generally a type of SiO2 which is amorphous and porous. The voids in the structure of silica gel enable it to adsorb moisture. Its melting point is around 1200°C and its electrical resistivity is 1015 ohm-cm. It changes its color when it adsorbs the humidity. In the present case, blue color spherical silica gel changes its color from blue to light pink when it is get saturated with moisture. It is nontoxic but should be kept away from the reach of children.