Composite Absorbent Research Articles

Composite adsorbents of CaCl2 and sawdust prepared by carbonization for ammonia adsorption refrigeration

Composite adsorbents of CaCl2 and sawdust prepared by carbonization for adsorption refrigeration with NH3 as refrigerant are tested, and the effects of carbonization temperature on the sorption capacity and rate are analyzed. The results show that the amount of pores in the sawdust of the composite adsorbents carbonized, apart from the content of CaCl2, is the most dominant factor influencing the NH3 sorption on composite adsorbents. The optimum carbonization temperature is 700°C, which gives the maximal NH3 sorption capacity as high as 0.774 kg of NH3 per kg of the composite, and the specific cooling power is approximately between 338 and 869 W/kg with the cycle duration varying from 5 to 20 minutes. The present study demonstrates that the composite absorbent of CaCl2 and sawdust prepared by carbonization is more promising and competitive for adsorption refrigeration application.

Poly(vinyl alcohol)/quaternized lignin composite absorbent: Synthesis, characterization and application for nitrate adsorption

AbstractA new poly(vinyl alcohol) (PVA)/quaternized lignin composite absorbent (PVA/QL) was synthesized from modified lignin and PVA, crosslinked by glutaraldehyde. As‐prepared absorbent was characterized by IR, DSC, SEM BET, and DMA. Effects of shaking time, absorbent dose, initial pH, and temperature on NO3− removal from aqueous solution by the absorbent were comprehensively investigated. The results show that the PVA/QL absorbent comprises quaternary ammonium groups in the form of ether bond. The composite absorbent exhibits remarkable network structure with large numbers of connected holes. The mechanical strength of the absorbent is enhanced by combining of PVA with modified lignin and crosslinkage of glutaraldehyde. The effect of pH on adsorption of NO3− is apparent and appropriate pH is 2.0. The adsorption process is endothermic, and determined to be consistent with the Langmuir isotherm. Furthermore, it is found that the quaternary ammonium structure and network structure in the surface of PVA/QL are the key factors to remove nitrate. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Experimental study on simultaneous desulfurization and denitrification from flue gas with composite absorbent

AbstractThe characteristics of desulfurization and denitrification with composite absorbent were researched through aqueous absorption experiments. The removal efficiencies of SO2 and NO were up to 100 and 95%, respectively. The composite absorbent included NaClO2 and component M. Existence of component M in the solution could reduce the absorbent cost compared with using sodium chlorite alone. Chlorine dioxide, as main reaction intermediate product, participated in oxidation reaction. The optimal experimental conditions involved NaClO2 concentration of1.13 mmol/L, solution pH of 5.5, molar ratio (M/NaClO2) of 4.1, reaction temperature of 323 K. The optimal solution pH and reaction temperature were both in the required ranges of limestone‐gypsum wet flue gas desulfurization (FGD) process. The research could offer primary data and important references for simultaneous removal of SO2 and NOx in limestone‐gypsum wet FGD process. © 2010 American Institute of Chemical Engineers Environ Prog, 2011

Removal of lead from aqueous solution by hydroxyapatite/magnetite composite adsorbent

A novel composite adsorbent, hydroxyapatite/magnetite (HAp/Fe 3O 4), has been prepared for the purpose of removing lead ions from aqueous solution. Varying factors that may affect the adsorption efficiency, including adsorbent dosage, solution pH and coexistent substances such as humic acid and competing cations (Ca 2+, Mg 2+, K + and Na +), have been investigated. It is remarkable that using the developed composite absorbent, more than 99% of Pb 2+ can be removed under desirable experimental conditions. The maximum adsorption capacity for HAp/Fe 3O 4 is 598.8 mg/g, which is much greater than that for the previously reported materials. It is found that depending on its concentrations, humic acid affects the efficiency of lead removal, but the coexisting cations, e.g., K +, Ca 2+, Na + and Mg 2+, have small influence. Mechanistic studies show that the adsorption data fits the Langmuir and Freundlich isotherm models reasonably well and the adsorption processes obey the pseudo-second-order kinetics model. Based on the experiment results, it is concluded that dissolution/precipitation and the surface complexation are mutually responsible for lead adsorption on HAp/Fe 3O 4, which should be attributed to the multiple functionalities of the material.