Superabsorbent hydrogels of poly(sodium acrylate) with crude and exfoliated vermiculites

2013 ◽  
Vol 33 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Antonio E. Mucientes ◽  
Francisca Santiago ◽  
Ana María Carrero ◽  
Beatriz Talavera
Keyword(s):  
Bound Water ◽  
Free Water ◽  
Clay Content ◽  
Absorption Capacity ◽  
Sodium Acrylate ◽  
Swelling Kinetics ◽  
Desorption Kinetics ◽  
Water Absorbency ◽  
Water Desorption ◽  
Superabsorbent Hydrogels

Abstract Novel superabsorbent hydrogels of poly(sodium acrylate) [poly(SA)] with crude vermiculite (CVMT) and exfoliated vermiculite (EVMT) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Both types of hybrids are more stable materials than poly(SA) and their thermal stability increases as the clay content increases. The equilibrium water absorbency for each hybrid type varies with the clay content, showing a maximum at 15 wt% and 20 wt% for EVMT and CVMT, respectively. The equilibrium water absorbency is higher for the hybrids than for poly(SA) at clay contents close to their maxima. The swelling kinetics obey a Voigt-based equation. The water desorption kinetics showed the existence of free water and bound water within the polymeric matrix. All of the superabsorbent materials investigated retained the water absorption capacity after repeating five wet-dry cycles.

Natural and Treated Hectorites/Poly(Sodium Acrylate) Hybrids: Synthesis, Characterization, and Properties

2010 ◽  
Vol 63 (10) ◽  
pp. 1462
Author(s):  
Antonio E. Mucientes ◽  
Francisca Santiago ◽  
Ana Carrero ◽  
Carlos Rivera
Keyword(s):  
Bound Water ◽  
Free Water ◽  
Clay Content ◽  
Sodium Acrylate ◽  
Swelling Kinetics ◽  
X Ray Diffraction ◽  
Transmission Electron Microscopy Analysis ◽  
Water Desorption ◽  
Transmission Electron ◽  
Electron Microscopy Analysis

Novel hybrids of poly(sodium acrylate) and natural and treated hectorites have been synthesized and characterized by X-ray diffraction, transmission electron microscopy analysis, and FTIR analysis. The thermal stability of these materials was studied. The swelling kinetics obey a Voigt-based equation. The experimental equilibrium water absorbency varies with the clay content and shows a minimum. All the hybrids showed excellent reswelling capability. Water desorption studies demonstrated the existence of ‘free water’ and ‘bound water’ within the polymeric matrix.

Synthesis and swelling behaviour of fast-swelling superabsorbent composites

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Fen Zhang ◽  
Mingzhu Liu ◽  
Xiaohua Qi ◽  
Zhenbin Chen
Keyword(s):  
High Water ◽  
Sodium Acrylate ◽  
Swelling Kinetics ◽  
Water Absorbency ◽  
High Porosity ◽  
Nacl Solution ◽  
Experimental Conditions ◽  
Swelling Equilibrium ◽  
Swelling Rate ◽  
Superabsorbent Composites

AbstractFast-swelling porous superabsorbent composites with high water absorbency in 0.9 wt% NaCl solution both at atmospheric pressure and under certain load (p ≈ 2×103 pa) were synthesized by a rapid solution polymerization of concentrated sodium acrylate, acrylamide and 2-hydroxypropyl acrylate. The porosity was induced through foaming conducted in the course of polymerization using acetone as porosity generator. The copolymerization and surface morphology of the porous copolymers were characterized by FTIR and SEM. To improve other properties of swollen hydrogel such as strength, resilience and dispersion, the copolymers were modified with inorganic salts after surfacecrosslinking by trihydroxymethyl propane glycidol ether. The influences of various experimental conditions, such as neutralization degree of acrylic acid, amount of initiator and crosslinker on the water absorbent capacity in 0.9 wt% NaCl solution were investigated. The resulting products under optimum conditions possessed the water absorbency of 65 g g-1 and 10 g g-1 in 0.9 wt% NaCl solution at atmosphere pressure and under load, respectively. The results of swelling kinetics measurement in 0.9 wt% NaCl solution showed that the composites had very fast swelling rate (they can reach swelling equilibrium in minutes). In addition, the effect of amount of acetone on swelling rate of the composites was examined in detail. It was shown that appropriate amount of acetone caused products with high porosity, which led to large swelling rate. Moreover, the swollen hydrogel exhibited excellent strength, better resilience and dispersion.

scholarly journals Cellulose Non Freezing Bound Water and Activation Energy of Desorption by Thermogravimetric Analysis

2021 ◽  
Author(s):  
Ricardo Klaus Kramer ◽  
Antonio José Felix Carvalho
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Cellulose Degradation ◽  
Bound Water ◽  
Free Water ◽  
Advanced Materials ◽  
Water Desorption ◽  
Processing Strategies ◽  
Key Factor ◽  
Activation Energy Of Desorption

Abstract Understand water-cellulose interaction isa key factor in cellulose processing strategies and to achieve the best propertiesfor each application. The emergence of new advanced materials based on nanocelluloses calls for more precise methods to study these systems. In this work, we described the study of water-cellulose interaction by thermogravimetric analysis (TGA), comparing dynamic and auto stepwise methods. The auto stepwise method was able to identify with precision the different species of water: i) the free water or freezing water, ii) the freezing bound water and iii) the non-freezing bound water. The Ozawa-Flynn-Wall method was used to estimate the activation energy of bound water desorption, Ea average = 50.45 kJ.mol-1 and the cellulose degradation energy, Ea average = 143.18 kJ.mol-1. The results obtained given a new knowledge on the interaction between water and cellulose since other techniques such as DSC are not sensitive to non-freezing bound water increasing the range of water content that can be studied.

Gelatin-G-Poly(Sodium Acrylate-co-Acrylamide)/Kaolin Superabsorbent Hydrogel Composites: Synthesis, Characterisation and Swelling Behaviour

2007 ◽  
Vol 15 (5) ◽  
pp. 395-402 ◽  
Author(s):  
G. Bagheri Marandi ◽  
H. Hosseinzadeh
Keyword(s):  
Crosslinking Agent ◽  
Ammonium Persulfate ◽  
Organic Polymer ◽  
Sodium Acrylate ◽  
Swelling Kinetics ◽  
Water Absorbency ◽  
Salt Solutions ◽  
Superabsorbent Hydrogel ◽  
Superabsorbent Composite ◽  
Aqueous Salt Solutions

A novel superabsorbent hydrogel composite based on gelatin has been prepared by graft copolymerisation of acrylic acid and acrylamide in the presence of kaolin powder, using methylene-bisacrylamide (MBA) as a crosslinking agent and ammonium persulfate as an initiator. The synthetic variables affecting the water absorbency of the resulting superabsorbent composite were studied and the composite structure was confirmed using FT-IR spectroscopy. A new absorption band at 1728 cm−1 in the composite spectrum confirmed the presence of a kaolin-organic polymer linkage. The effect of kaolin content and MBA concentration showed that increasing these parameters decreased the water absorbency of the superabsorbent composite. The swelling measurements were conducted in aqueous salt solutions. Results indicated that the swelling ratios decreased with an increase in the ionic strength of the salt solutions. The pH of the various solutions also affected the swelling of the superabsorbent. Finally, the swelling kinetics of synthesised composites with various absorbent particle sizes was briefly examined.

Determine the Moisture Distribution in Sewage Sludge by Drying Differential

2014 ◽  
Vol 665 ◽  
pp. 404-407 ◽  
Author(s):  
Wan Yu ◽  
Pei Sheng Li
Keyword(s):  
Sewage Sludge ◽  
Interstitial Water ◽  
Bound Water ◽  
Free Water ◽  
High Accuracy ◽  
Moisture Distribution ◽  
Municipal Sewage ◽  
Municipal Sewage Sludge ◽  
Hot Air ◽  
Critical Water Content

Moisture distribution in sewage sludge was considered as the essential of thermal drying. Some methods were given in literatures to test the moisture distribution, but there was no standard method to determine the critical water content between different kinds of water. The municipal sewage sludge was dried by hot air in this work. Based on the drying curve, the derivative of drying rate with respect to dry basis moisture content was brought out to analyze the moisture distribution in sewage sludge. Results show that this method can easily determine the free water, interstitial water, surface water and bound water with a high accuracy. The present work can provide new insight to determine the moisture distribution in sewage sludge, which was still lacking in the literatures.

Dynamic Study on Vacuum Pyrolysis Reaction of Chinese Fir Sawdust Biomass

2012 ◽  
Vol 512-515 ◽  
pp. 375-378
Author(s):  
Su Wen Yang ◽  
Jian Min Yi ◽  
Ke Qiang Qiu ◽  
Xin Deng ◽  
Jian Shan Chen
Keyword(s):  
Heating Rate ◽  
Free Water ◽  
Chinese Fir ◽  
Peak Temperature ◽  
Gravimetric Analysis ◽  
Water Desorption ◽  
Exponential Factor ◽  
Pyrolysis Reaction ◽  
Temperature Range ◽  
Vacuum Pyrolysis

This thesis does thermal gravimetric analysis（TGA）studies on Chinese fir sawdust biomass by integrated thermal analyzer under vacuum conditions. Through the analysis on lostmass curve at different heating rate of 10, 15, 20 and 30°C/min, we found the process of Chinese fir sawdust vacuum pyrolysis can be mainly divided into three stages: evaporation of free water and combined water desorption, rapid lostmass of pyrolysis and slow decomposition of residues. The lostmass major temperature range is between 250 ~ 450°C, the peak temperature is between 365 ~ 400°C. When the pyrolysis temperature is 500°C, vacuum pyrolysis reaction of Chinese fir sawdust has basically completed. As the heating rate rises, the lostmass curve is moving to the right, the peak temperature is shifting to higher temperature, and the temperature range of thermal decomposition reaction widens significantly. According to experimental datas, we tried to obtain the vacuum pyrolysis dynamic parameters of Chinese fir sawdust, and the results are that the apparent activation energy of vacuum pyrolysis reaction of Chinese fir sawdust biomass is 128.34kJ/mol, with the pre-exponential factor being 6.42×109 and reaction order being 1.08, similar to first order reaction.

scholarly journals Testing the effects of basic numerical implementations of water migration on models of subduction dynamics

Solid Earth ◽  
2014 ◽  
Vol 5 (1) ◽  
pp. 537-555 ◽  
Author(s):  
M. E. T. Quinquis ◽  
S. J. H. Buiter
Keyword(s):  
Upper Mantle ◽  
Water Distribution ◽  
Mantle Wedge ◽  
Bound Water ◽  
Free Water ◽  
Water Velocity ◽  
Water Migration ◽  
Creep Flow ◽  
Dehydration Reactions ◽  
Slab Dehydration

Abstract. Subduction of oceanic lithosphere brings water into the Earth's upper mantle. Previous numerical studies have shown how slab dehydration and mantle hydration can impact the dynamics of a subduction system by allowing a more vigorous mantle flow and promoting localisation of deformation in the lithosphere and mantle. The depths at which dehydration reactions occur in the hydrated portions of the slab are well constrained in these models by thermodynamic calculations. However, computational models use different numerical schemes to simulate the migration of free water. We aim to show the influence of the numerical scheme of free water migration on the dynamics of the upper mantle and more specifically the mantle wedge. We investigate the following three simple migration schemes with a finite-element model: (1) element-wise vertical migration of free water, occurring independent of the flow of the solid phase; (2) an imposed vertical free water velocity; and (3) a Darcy velocity, where the free water velocity is a function of the pressure gradient caused by the difference in density between water and the surrounding rocks. In addition, the flow of the solid material field also moves the free water in the imposed vertical velocity and Darcy schemes. We first test the influence of the water migration scheme using a simple model that simulates the sinking of a cold, hydrated cylinder into a dry, warm mantle. We find that the free water migration scheme has only a limited impact on the water distribution after 1 Myr in these models. We next investigate slab dehydration and mantle hydration with a thermomechanical subduction model that includes brittle behaviour and viscous water-dependent creep flow laws. Our models demonstrate that the bound water distribution is not greatly influenced by the water migration scheme whereas the free water distribution is. We find that a bound water-dependent creep flow law results in a broader area of hydration in the mantle wedge, which feeds back to the dynamics of the system by the associated weakening. This finding underlines the importance of using dynamic time evolution models to investigate the effects of (de)hydration. We also show that hydrated material can be transported down to the base of the upper mantle at 670 km. Although (de)hydration processes influence subduction dynamics, we find that the exact numerical implementation of free water migration is not important in the basic schemes we investigated. A simple implementation of water migration could be sufficient for a first-order impression of the effects of water for studies that focus on large-scale features of subduction dynamics.

Characterization of thin water layers in pulp by tritium exchange. Part 1: Methods development

Holzforschung ◽  
2007 ◽  
Vol 61 (2) ◽  
pp. 115-119 ◽  
Author(s):  
Frances L. Walsh ◽  
Sujit Banerjee
Keyword(s):  
Water Content ◽  
Surface Area ◽  
Tritiated Water ◽  
Bound Water ◽  
Free Water ◽  
Fiber Surface ◽  
Bulk Water ◽  
Methods Development ◽  
A Value ◽  
A New Technique

Abstract A new technique for measuring the monolayer water content of fiber is presented. Tritiated water is added to a pulp/water suspension, whereupon the tritium partitions between the bulk water and the pulp. In the pulp phase the tritium can exchange with free water, bound water, and with hydroxyl and other protons present in the pulp matrix. The free water in the pulp is then removed by displacement with acetone. The tritium remaining in the pulp is mostly associated with tightly bound water, with a small fraction being tied up with the exchangeable hydrogen in pulp. The procedure provides a value of 10% for the tightly bound water content of hardwood or softwood fiber, either bleached or unbleached. If this water is assumed to cover the fiber surface as a monolayer, then an estimate of the wet surface area of the fiber can be obtained. This estimate compares well with independent measurements of surface area.

Preparation and Swelling Properties of P(AMPS-co-AM)/ Attapulgite Clay Superabsorbent Composite by Microwave Irradiation

2012 ◽  
Vol 512-515 ◽  
pp. 2394-2398 ◽  
Author(s):  
Ji Hong Xu ◽  
De Xin Tan ◽  
Ling Yan Yan ◽  
Zhong Li
Keyword(s):  
Microwave Irradiation ◽  
Microwave Power ◽  
Water Retention ◽  
Salt Water ◽  
Absorption Capacity ◽  
Water Absorbency ◽  
Swelling Properties ◽  
Superabsorbent Composite ◽  
Speed Up ◽  
Attapulgite Clay

A novel poly(2-acrylamido-2-methylpropa-nesulfonicacid-co-acrylamide) / attapulgite (P(AMPS-co-AM)/APT) high-salt superabsorbent composite was synthesized through graft polymerization in aqueous solution by microwave irradiation. The structure of the composite was characterized by infrared spectra (FTIR).The influence of the content of monomer, microwave power and the ratio of attapulgite clay on water absorbency was investigated. The swelling behaviors and the water retention of Superabsorbent resin with different APT content were also examined. The results show that the graft copolymerization took place between APT and organic monomers. Adding an appropriate amount of APT in resin can effectively improve the absorption capacity and salt-water performance. Microwave power is 390W, APT amount is 7.5% (mass fraction),The water absorbency of resin in distilled water and 0.9wt% NaCl were 1460g / g and 114 g / g. The resin has a faster absorption rate and strong water retention, the appropriate increase the amount of APT can significantly speed up the rate of the resin absorbent and improve its water retention.

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