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Hydrogels have been widely used in water purification. However, there is not much discussion and comparison about the effects of different nanofillers on the reinforcement and adsorption performances of hydrogels, which can be subjected to rapid water flow and possess strong adsorption ability. In this work, polyacrylamide (PAAM)-sodium alginate (SA) interpenetrating polymer network-structured hydrogels were prepared by in situ polymerization. PAAM formed the first flexible network and SA constructed the second rigid network. Three kinds of inorganic nanoparticles including carbon nanotubes (CNTs), nanoclays (NCs), and nanosilicas (NSs) were incorporated into a PAAM-SA matrix via hydrogen bond. The obtained hydrogels exhibited a macroporous structure with low density (≈1.4 g/cm3) and high water content (≈83%). Compared with neat PAAM-SA, the hydrogels with inorganic nanoparticles possessed excellent mechanical strengths and elasticities, and the compression strength of PAAM-SA-NS reached up to 1.3 MPa at ε = 60% by adding only 0.036 g NS in a 30 g polymer matrix. However, CNT was the best filler to improve the adsorption capacity owing to its multi-walled hollow nanostructure, and the adsorption capacity of PAAM-SA-CNT was 1.28 times higher than that of PAAM-SA. The prepared hydrogels can be potential candidates for use as absorbents to treat wastewater.

• Thermo/pH responsive Poly(N-isopropylacrylamide)/sodium alginate hydrogels were prepared. • Cellulose nanofibers (TOCNF) acted as a dispersant to assist the dispersion of inorganic fillers. • The hydrogels were homogeneous and stable with a macro-porous structure. • The compressive strength was enhanced by incorporating organic and inorganic nanofillers. • The hydrogels exhibited reversible temperature dependent on–off fluorescence properties. The incorporation of renewable bio-based materials/eco-friendly inorganic nanofillers into stimuli-responsive hydrogels meets the need for biocompatible and non-toxic functional materials. However, it remains challenging to build a three-dimensional network with enhanced mechanical properties and desired stimuli-responsive performances. In this study, dual stimuli-responsive hydrogels with interpenetrating polymer network structure are fabricated by the crosslinking of N-isopropylacrylamide (NIPAM) 1 1 NIPAM: N-isopropylacrylamide and sodium alginate (SA) 2 2 SA: Sodium alginate. 2,2,6,6-tetramethyl-piperidine-1-oxyl-oxidized cellulose nanofibers (TOCNF) 3 3 TOCNF: 2,2,6,6-tetramethyl-piperidine-1-oxyl-oxidized cellulose nanofibers derived from energycane bagasse serves as a carrier material for nanosilicas (NS) 4 4 NS: Nanosilicas and nanoclays (NC) 5 5 NC: Nanoclays and the effects of TOCNF, TOCNF/NS and TOCNF/NC on the hydrogels are thoroughly explored. Among these hydrogels, PNIPAM/SA-TOCNF-NS possesses the largest compressive strength of 66.7 kPa and it is 5.65 times higher than that of PNIPAM/SA. The thermo-sensitivity and pH-sensitivity of hydrogels are evidenced by swelling behaviors, optical properties, contact angle measurements and fluorescence tests. PNIPAM/SA-TOCNF exhibits the largest contact angle and the swelling processes for all the hydrogels are well fitted by pseudo-second-order swelling kinetic model. In addition, after incorporating carbon quantum dots, all the hydrogels display temperature dependent on–off fluorescence properties and this process are fully reversible with the heating and cooling cycles. These novel hydrogels with pH and temperature responsive characteristics and remarkable mechanical properties will open the door for interesting applications in smart sensors etc. [ABSTRACT FROM AUTHOR]

Hydrogels have been widely used in water purification. However, there is not much discussion and comparison about the effects of different nanofillers on the reinforcement and adsorption performances of hydrogels, which can be subjected to rapid water flow and possess strong adsorption ability. In this work, polyacrylamide (PAAM)-sodium alginate (SA) interpenetrating polymer network-structured hydrogels were prepared by in situ polymerization. PAAM formed the first flexible network and SA constructed the second rigid network. Three kinds of inorganic nanoparticles including carbon nanotubes (CNTs), nanoclays (NCs), and nanosilicas (NSs) were incorporated into a PAAM-SA matrix via hydrogen bond. The obtained hydrogels exhibited a macroporous structure with low density (≈1.4 g/cm3) and high water content (≈83%). Compared with neat PAAM-SA, the hydrogels with inorganic nanoparticles possessed excellent mechanical strengths and elasticities, and the compression strength of PAAM-SA-NS reached up to 1.3 MPa at ε = 60% by adding only 0.036 g NS in a 30 g polymer matrix. However, CNT was the best filler to improve the adsorption capacity owing to its multi-walled hollow nanostructure, and the adsorption capacity of PAAM-SA-CNT was 1.28 times higher than that of PAAM-SA. The prepared hydrogels can be potential candidates for use as absorbents to treat wastewater. [ABSTRACT FROM AUTHOR]