Development of a superporous hydroxyethyl cellulose-based hydrogel by anionic surfactant micelle templating with fast swelling and superabsorbent properties

Effect of chain structures of monomer on hydroxyethyl cellulose-based superabsorbent properties and improvement of chickpeas plant growth of water deficit-stressed

The aim of this research was evaluation of the influence of distance between zwitterionic monomer ions on the performance of superabsorbents. For this purpose, two zwitterionic monomers 4-(3-aminopropyl) amino-4-oxo-2-butenoic acid (APOB) and 4-(6-aminohexyl) amino-4-oxo-2-butenoic acid (AHOB) were prepared and applied for synthesis of two new superabsorbents through graft copolymerization onto hydroxyethyl cellulose (HEC) in the presence of acrylic acid (AA). In synthesis of superabsorbents factors such as the highest water absorbency capacity, absorbency rate, gel strength, and environmental problems should be resolved or improved. The results demonstrated that the water absorbency capacity and rate parameters (τ) of HEC-g-p(AA-co-APOB) and HEC-g-p(AA-co-AHOB) in distilled water were 986.62, 664.38 g/g, and 98.04, 140.84 min, respectively. The biodegradability of HEC-g-p(AA-co-APOB) was approximately 4 times more than HEC-g-p(AA-co-AHOB). However, based on the rheological analyses (G'/G″) HEC-g-p(AA-co-AHOB) was stronger than the other. Additionally, studies of water retention on soil containing HEC-g-p(AA-co-AHOB) superabsorbent (soil with 0.25 wt% material) showed that the after 30 days has ≤5 % water while soil in the absence of superabsorbent after 10 days completely dried. Studies of the growth of plants in soil demonstrated in the presence of HEC-g-p(AA-co-AHOB) the average length of shoots was 36 cm while without superabsorbent were 25 cm.

Maleic acid as an important monomer in synthesis of stimuli-responsive poly(acrylic acid-co-acrylamide-co-maleic acid) superabsorbent polymer

Poly(acrylic acid-co-acrylamide-co-maleic acid) (p(AA-co-AM-co-MA)) superabsorbent polymer was synthesized from acrylic acid (AA), acrylamide (AM), and maleic acid (MA) via free radical copolymerization. Results showed the presence of maleic acid in structure of superabsorbent has the key and superior role in creating a smart superabsorbent. The structure, morphology, and strength of the superabsorbent were characterized using FT-IR, TGA, SEM, and rheology analysis. The effect of different factors was investigated to determine the ability of water absorbency of the superabsorbent. According to optimized conditions, the water absorbency capacity of the superabsorbent in distilled water (DW) was 1348 g/g and in a solution containing 1.0 wt.% NaCl (SCS) was 106 g/g. The water retention ability of the superabsorbent was also investigated. The kinetic swelling of superabsorbent was identified by Fickian diffusion and Schott's pseudo-second-order model. Furthermore, the reusability of superabsorbent was studied in distilled water and saline solution. The ability of superabsorbent was investigated in simulated urea and glucose solutions, and very good results were obtained. The response ability of the superabsorbent was confirmed by swelling and shrinking behavior against changes of temperature, pH, and ionic strength.

Synthesis of a novel superabsorbent with slow-release urea fertilizer using modified cellulose as a grafting agent and flexible copolymer

In this work, a number of glucose unites in polymeric structure of cellulose was converted to 2,4-dihydroxy-3-(1-hydroxy-2-oxoethoxy)butanal (cellulose containing di aldehyde units (CCDAUs)) by oxidation with sodium periodate, followed by condensation with acetone to produce 5,7-dihydroxy-6-((1-hydroxy-4-oxopent-2-en-1-yl)oxy)hept-3-en-2-one unites (cellulose containing di ene units (CCDEUs)). This modified cellulose was characterized by different methods and applied as a copolymer and grafting agent to synthesize an eco-friendly (CCDEUs-g-poly(AA)/urea) superabsorbent with slow-release urea fertilizer. The created double bonds in C₂ and C₃ positions of β-d-glucose units increased the linkage between cellulose and acrylic acid, leading to the formation of a strong network for slow-release urea fertilizer. Also, this modification created an expanded network for storage a high amount of water by increasing the cellulose flexibility. The reaction conditions for modification and synthesis of the superabsorbent, the oxidation degree value of glucose units, kinetics models, the effect of different saline solutions, various pH and reswelling time on the water absorbency, water retention capacity, reusability, biodegradability, and slow-release property were investigated. Also, the effect of synthesized CCDEUs-g-poly(AA)/urea on plant growth was tested and excellent results were obtained.

A solution blown superporous nonwoven hydrogel based on hydroxypropyl cellulose

A superporous hydrogel - in which the interconnecting fibres themselves are hydrogels - based on hydroxypropyl cellulose (HPC) has been produced using the nonwoven solution blown technique. The nonwoven fibres were subsequently thermally crosslinked with citric acid as identified by esterbond formation using FT-IR spectroscopy. The gel fraction was approximately 70%. The superporous HPC hydrogel exhibited a very fast water absorption, reaching an equilibrium absorption (80% water content) within 30 seconds. The equilibrium absorption was strongly codependent on both the fibre thickness and the pore size whereas the absorption rate was correlated with the pore size as established using standard linearized regression analysis.

Eco-friendly porous carboxymethyl cellulose/dextran sulfate composite beads as reusable and efficient adsorbents of cationic dye methylene blue

Eco-friendly hydrogel composite beads based on crosslinked-carboxymethyl cellulose (CMC) and dextran sulfate (DS) embedded within network were prepared using ionotropic gelation in presence of sodium n-dodecyl sulfate (SDS) as pore-forming template. The milligels composites C/Dx were characterized by FTIR, SEM/EDX and TGA analyses. The composites exhibited porous structure and enhance in swelling properties with enriching DS as well as pH-sensitivity. The effect of DS on adsorption of composites for cationic dye methylene blue (MB) was investigated by changing influencing factors: pH, adsorbent dosage, time contact, dye concentration, and temperature. The results revealed that adsorption performances were remarkably improved by increasing DS content into beads. Kinetics and isotherm adsorption studies revealed pseudo second-order and Langmuir isotherm as befitting models. The maximum Langmuir equilibrium adsorption capacity (q_m) was found to increase from 82 mg g^-1 for C/D0 to 526 mg g^-1 for C/D1. Thermodynamic study revealed spontaneous and endothermic process nature. Furthermore, milligels displayed good reusability after five adsorption/desorption cycles and with an augment in their removal ability compared to starting ones, reaching 714 mg g^-1 for R-C/D1. In view of easy preparation and recovery, effectiveness adsorption and good regeneration, the composites could be applied as low-cost adsorbents in wastewater treatment.