Synthesis, swelling behaviors, and slow‐release characteristics of a guar gum‐g‐poly(sodium acrylate)/sodium humate superabsorbent

Abstract

Superabsorbents used in agricultural and ecological projects with low-cost, slow-release fertilizers and environmentally friendly characteristics have been extensively studied. The use of a natural polymer as the matrix and then further polymerization with some functional material has become the preferred method. In this work, with natural guar gum (GG), partially neutralized acrylic acid, and sodium humate (SH) as the raw materials, ammonium persulfate as the initiator, and N,N 0 -methylenebisacrylamide (MBA) as the crosslinker, GG-gpoly(sodium acrylate) (PNaA)/SH superabsorbents were synthesized through a solution polymerization reaction and were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The effects of the SH content and MBA concentration on the water absorbency were investigated. The results showed that the introduction of SH into the GG-g-PNaA system could improve the water absorbency, swelling rate, pH-resistant property, and reswelling capability, and the superabsorbent containing 15 wt % SH had the highest water absorbency of 532 g/g of sample in distilled water and 62 g/g of sample in a 0.9 wt % NaCl solution. The slow release in water and water retention in sandy soil tests revealed that the superabsorbent could act as a fertilizer as well as an effective water-saving material for agricultural applications.

Synthesis, characterization, and swelling behaviors of chitosan‐g‐poly(acrylic acid)/poly(vinyl alcohol) semi‐IPN superabsorbent hydrogels

“…As can be noticed, the water absorbency almost maintains constant in the pH range of 4–9 for CTS‐ g ‐PAA, 4–10 for CTS‐ g ‐PAA/PVA with 5 wt% PVA, and 4–11 for CTS‐ g ‐PAA/PVA with 10 wt% PVA semi‐IPN superabsorbent hydrogel, respectively. According to previous report,35, 36 this behavior is attributed to the buffer action of COOH and COO − groups with weak acid or weak base. In comparison with CTS‐ g ‐PAA, the adaptive range of CTS‐ g ‐PAA/PVA to pH was widen and the widen degree increases with increasing the content of PVA, which indicate that the introduction of nonionic PVA and the formation of semi‐IPN structure enhanced the buffer action of COOH and COO − groups and improved the pH‐stability of the superabsorbent hydrogels, and the adaptive range of the hydrogels can also be controlled by altering the content of PVA.…”

Effects of Modified Vermiculite on Water Absorbency and Swelling Behavior of Chitosan-g-Poly(Acrylic Acid)/Vermiculite Superabsorbent Composite

“…COO groups can combine with H + of the external solution under an acidic condition, and COOH groups can react with external OH to convert to COO under a basic condition. As a result, the amount of H + and OH in the external solution may decrease in the pH range of 411 because of the buffer action of COOH and COO groups [32]. When the pH of external solution increases from 2 to 4, the ionized degree of these hydrophilic groups increase, which result in an increase in osmotic pressure between polymeric network and external solution as well as electrostatic repulsion among carboxylate groups inside the polymer matrix [33].…”

Reuse of a waste adsorbent poly(AAc/AM/SH)‐Cu superabsorbent hydrogel, for the potential phosphate ion removal from waste water: Matrix effects, adsorption kinetics, and thermodynamic studies

“…It consists of multifunctional aliphatic components and aromatic constituents that contain large number of functional hydrophilic groups (including carboxylates and phenolic hydroxyls, NH 2 groups and oxygen and nitrogen as bridge units). 21 Presence of these carboxylate and phenolate groups helps sodium humate to form complexes/chelates with metal ions.…”