Preparation, swelling behaviors and application of polyacrylamide/attapulgite superabsorbent composites

Abstract

A series of superabsorbent composites, polyacrylamide/attapulgite (PAMA), were prepared from acrylamide (AM) and attapulgite micropowder in aqueous solution, using N,N 0 -methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator and then saponified with sodium hydroxide solution. This paper focuses on swelling behaviors of the PAMA superabsorbent composites in various saline solutions. The results indicate that saline solutions can weaken the swelling abilities of the PAMA compsites greatly. Water absorbency of the PAMA composites with 20 and 40 wt% attapulgite in aqueous chloride salt solutions has the following order:However, swelling properties of the composites are complicated in CuCl 2(aq) , AlCl 3(aq) and FeCl 3(aq) solutions and are related to saline solutions concentration. The deswelling behavior of PAMA composites is more obvious in univalent chloride salt solutions than in divalent and trivalent ones. The influence of kind and valence of anions on swelling ability of the composites is limited and almost the same. Moreover, reswelling capability, practical water retention ability in sand soil of the composites and the effect of pH on water absorbency of the PAMA composites were investigated. The PAMA composite shows good water retention and reswelling ability in sand soil, and may be used as a recyclable water-managing material for the renewal of arid and desert environment.the effect of pH on water absorbency of the PAMA composite are investigated. EXPERIMENTAL MaterialsAcrylamide (Am, analytical grade, supplied by Shanghai Chemical Factory, Shanghai, China) was purified by a method as reported in the literature. 20 The initiator, ammonium persulfate (APS, analytical grade, supplied by Xi'an Chemical Reagent Factory, Xi'an, China), was recrystallized from water before use. The crosslinker, N,N 0 -methylenebisacrylamide (MBA, chemically pure, supplied by Shanghai Chemical Reagent Corp., Shanghai, China), was used as purchased. Attapulgite micropowder (supplied by Linze Colloidal Co., Gansu, China) was milled through a 320-mesh screen and treated with 37% hydrochloric acid for 72 hr, followed by washing with distilled water until pH 6 was achieved, and then dried at 1058C for 8 hr before use. Other agents used were all analytical grade and all solutions were prepared with distilled water.

Swelling behavior of polyacrylamide/laponite clay nanocomposite hydrogels: pH-sensitive property

“…Na + has no effect on -COO À and -CONH 2 groups, and the decrease of water absorbency for PAAm composite is mainly due to the decrease of osmotic pressure and the screening effect. These results are all consistent with the decreasing of water absorbency for PAAm composite and the corresponding interpretation reported elsewhere [28]. The well-known relationship between the swelling and salt solution concentration is stated in Eq.…”

Study on swelling behavior of poly(sodium acrylate-co-2-acryloylamino-2-methyl-1-propanesulfonic acid)/attapulgite macroporous superabsorbent composite

“…It can be seen from the Fig. that the water absorbency decreases with increasing ionic strength of NaCl solution as reported by other works . It is caused by the reduction of the osmotic pressure between sample and external swelling medium.…”

“…Conversely, the hydration radius of various cations increase as follows: K + , NH 4 + , Na + , Ba 2+ , Ca 2+ , Mg 2+ , Al 3+ . The cation with small hydration radius has high charge density, which gives an evident screening effect on the anionic groups of polymer chains, and leads to low equilibrium water absorbency . In addition, for eliminating the effect of ionic strength on equilibrium water absorbency, all solutions were adjusted to the same ionic strength.…”

“…However, compared with divalent anions, the equilibrium water absorbency of sample in swelling medium with monovalent anions and a common cation (Na + ) decreases a little. The same results are also reported by Zhang et al . When the ionic strength of swelling medium containing monovalent anion is equal to that of divalent anion, the concentration of Na + in swelling medium containing monovalent anion is more than that with divalent anion.…”

Synergistic effect of poly(acrylamide)-incorporated poly(L-ascorbic acid) hydrogels in controlled release and wound dressings

“…This will also decrease the water absorbency for both hydrogel specimens. [52,53] Figure 6(b) displays the effect of dose on swelling (%) of hydrogel specimens from different contents of PLAA inside hydrogel structures. Generally, it was observed that by increasing exposure radiation dose, the swelling of gel decreases.…”