Efficiency of Magnetic Granular Adsorbent Based on Natural Zeolite/Chitosan in Removing Arsenic from Polluted Water

Hypothesis: Among the various pollutants found in natural water, the heavy metal arsenic is more important due to its high toxicity. One of the most efficient methods to remove this pollution from water streams is the surface adsorption method. Zeolite nanocomposites can be considered powerful among arsenic adsorbers. Powder adsorbents are not very effective in industrial systems due to the problems such as clogging of filters, high pressure drop and also the problem of separation from water.Methods: To solve this problem, zeolite nanocomposite powder was transformed into beads using the chitosan gel method in three different types of cross-linking solutions including sodium hydroxide, sodium tripolyphosphate and joint sodium hydroxide/sodium tripolyphosphate. The effect of various parameters such as the type and initial ratio of the materials on the formation of beads was investigated.Findings: The results showed that the beads formed in the sodium hydroxide+sodium tripolyphosphate cross-linking solution and the optimal initial ratio of 1:3 from chitosan to the nanocomposite have a more suitable appearance and strength and better performance in arsenic absorption. In order to confirm and justify the mentioned Findings, SEM, BET and AAS analyses were performed. Operational parameters of initial arsenic concentration and adsorbent dose which are effective on the beads’ adsorption efficiency were investigated and the optimal amount of adsorbent dose was determined as 1 g/L with an efficiency of 92.9%. In order to obtain more information about the method of adsorption and determining the maximum capacity of adsorbents, Langmuir and Freundlich isotherms for granular adsorbents were investigated. The highest adsorption capacity of 7450.7 mg/g was obtained and Freundlich isotherm was in better agreement with the results

Modeling the size of hydrophilic nanoparticles during fluidization with emphasis on the role of vapor of polar materials

In this study, a comprehensive force balance model is developed to estimate the equilibrium size of agglomerates formed during the fluidization of nanoparticles with considering the importance of hydrogen bond, van der Waals and gravitational forces. Also, the influence of vapor of different polar materials (including methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and ammonia) on the size of hydrophilic silica nanoagglomerates and consequently their fluidization behavior is studied by experiments in a gas-solid fluidized bed. The results show that using vapor of these polar materials (with hydroxyl groups in their formula) improves the fluidization behavior of hydrophilic silica nanoparticles significantly and results in a higher bed expansion. To justify the improving effect of different vapor of polar materials on fluidization behavior, the electrostatic repulsion force is added to the model and size of agglomerates are calculated in the presence of this force. It is obtained that the results of model are in good agreement with the experimental observations, so that, among all used materials methanol, 2-propanol and ethanol have the most effective impact on fluidization improvement and the smallest size of agglomerates is estimated using physical properties of these three alcohols as well.  Finally, the size of agglomerates calculated by the model shows error less than 11% compared with the size of agglomerates measured experimentally by laser. This error is lower than the previous reported ones in the literature

O OR RI IG GI IN NA AL L A AR RT TI IC CL LE E Investigation the Important Traits of Spring Safflower Varieties through Multivariate Statistical Methods

ABSTRACT Due to the growing demand for edible oils, oilseed crop development is very important. Safflower (Carthamus tinctorius L) is a native o

Metal- based eggshell particles prepared via successive incipient wetness impregnation method as a promoted sorbent for CO<inf>2</inf> capturing in the calcium looping process

Cyclic adsorption by using of bio-waste eggshell particles as a cheap, accessible and environmentally friendly CaCO3 source has been considered as one of the important methods to decrease or remove CO2 from the flue gas. However, deactivation of eggshell particles and CO2 capture capacity decaying with increasing the cycle's number remained as an important challenge. Using metal nitrates as one of the modification methods has been proposed by the researchers to overcome this problem. Current study investigates the influence of three metal nitrates of Al, La and Mg added to the eggshell particles via successive incipient wetness impregnation (SIWI) method to improve their adsorption performance. The TGA results at the end of the 20th carbonation/calcination cycle revealed a meaningful relationship between CaO molar conversion of eggshell modified with metal nitrates and their crystallite size as well as the surface area of the sorbents, so that the smaller the crystal size and the larger the surface area, the higher the molar conversion of CaO could be achieved. Due to the highest conversion obtained for Mg-containing sample, the effect of different weight percentages of this additive was also investigated. Results showed that 5 wt% MgO contained eggshell particles could be reported as the most outstanding sample for its improved molar conversion, capture capacity at the end of 20th carbonation/calcination cycle and BET surface area, which were 30.18%, 0.23 gr CO2/gr adsorbent and 3.5 m2/g while the corresponding amounts for raw eggshell were 17.26%, 0.11 gr CO2/gr adsorbent and 1.63 m2/g, respectively.This work was supported by Iran National Science Foundation (INSF), (contracts No. 99011962).Peer reviewe

CO2 capture activity of a novel CaO adsorbent stabilized with (ZrO2+Al2O3+CeO2)-based additive under mild and realistic calcium looping conditions

The present investigation concentrated on the configuration of a novel synthetic adsorbent via the sol-gel auto-combustion method through incorporating ZrO2, Al2O3, and CeO2 simultaneously during the development of CaO adsorbent. The impacts of disparate calcium precursors and molar ratios of calcium precursors to promoters were also studied. The adsorbent developed from soluble calcium nitrate precursor showed the higher surface area and smaller CaO grain size accompanied by a more enhanced capture capacity and CaO conversion at the mild and realistic process conditions during the carbonation-calcination cycles. Among synthesized adsorbents with disparate the molar ratio of Ca/(Ze + Al + Ce) (calcium precursor: promoters), the prepared sample with the molar ratio of 20/1 (CN/20) indicated the most promising performance with the best morphological properties, higher sorption capacity, and CaO conversion in comparison with 15/1 (CN/15) and 30/1 (CN/30) during 18 carbonation-calcination multiple cycles under the realistic condition. The most highlighted result of this work was that cyclic performance of modified adsorbents is linearly proportional to their morphological properties, in that CN/20 with the largest free surface area of 31.3 m2/g captured 4.23 g CO2/gr adsorbent, 9.58 % and 11.6 % higher than that captured by CN/15 and CN/30, respectively, during 18 realistic carbonation/calcination cycles.Peer reviewe

Theoretical and experimental study on the fluidity performance of hard-to-fluidize carbon nanotubes-based CO<inf>2</inf> capture sorbents

Carbon nanotubes-based materials have been identified as promising sorbents for efficient CO2 capture in fluidized beds, suffering from insufficient contact with CO2 for the high-level CO2 capture capacity. This study focuses on promoting the fluidizability of hard-to-fluidize pure and synthesized silica-coated amine-functionalized carbon nanotubes. The novel synthesized sorbent presents a superior sorption capacity of about 25 times higher than pure carbon nanotubes during 5 consecutive adsorption/regeneration cycles. The low-cost fluidizable-SiO2 nanoparticles are used as assistant material to improve the fluidity of carbon nanotubes-based sorbents. Results reveal that a minimum amount of 7.5 and 5 wt% SiO2 nanoparticles are required to achieve an agglomerate particulate fluidization behavior for pure and synthesized carbon nanotubes, respectively. Pure carbon nanotubes + 7.5 wt% SiO2 and synthesized carbon nanotubes + 5 wt% SiO2 indicates an agglomerate particulate fluidization characteristic, including the high-level bed expansion ratio, low minimum fluidization velocity (1.5 and 1.6 cms−1), high Richardson—Zaki n index (5.2 and 5.3 > 5), and low Π value (83.2 and 84.8 < 100, respectively). Chemical modification of carbon nanotubes causes not only enhanced CO2 uptake capacity but also decreases the required amount of silica additive to reach a homogeneous fluidization behavior for synthesized carbon nanotubes sorbent. [Figure not available: see fulltext.]Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.Peer reviewe