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Cu2O nanoparticle (NP)-functionalized cellulose-based aerogel (Cu2O/CBA) with three-dimensional (3D) macroporous structure and abundant active sites was successfully prepared for visible-light photocatalysis via in situ deposition of Cu2O NPs on cellulose-based aerogel (CBA). Octahedral Cu2O NPs were formed and anchored onto the surface and inner wall of the cellulose matrix, which acted as a microreactor to prevent aggregation and protect the catalytic character of the Cu2O NPs. The photocatalytic performance of the Cu2O/CBA composite catalysts was evaluated using degradation of methylene blue (MB) as model pollutant. The effects of catalyst dosage, initial MB concentration, and solution pH on MB photodegradation were investigated. Use of 3D macroporous CBA improved the MB adsorption capacity and extended the absorption of visible-light irradiation. In particular, in situ deposition of Cu2O in the cellulose matrix enhanced separation of photogenerated electrons and holes via surface-adsorbed molecular oxygen, and consequently the catalytic activity. The photodegradation rate of MB by Cu2O/CBA composite catalyst reached 95.79%, much higher than the value of 73.59% for pure Cu2O. The photodegradation process on the Cu2O/CBA composite catalysts followed an apparent pseudo-first-order kinetic model. The Cu2O/CBA composite catalyst was easily recycled and reused, with 80% MB degradation rate retained even after six cycles of irradiation for 30 min each. Such Cu2O/CBA composite catalysts can be applied for wastewater treatment utilizing solar radiation.

To understand the correlation between structural feature and removal capability, a series of cellulose-based bioadsorbents with controlled pore size and functional group contents were designed and synthesized by grafting acrylic acid and acrylamide onto cellulose backbone chains. The adsorption behavior of these bioadsorbents to three metal ions [Cr(III), Cu(II) and Co(II)] in aqueous solution was investigated. The correlation between structural feature of cellulose-based bioadsorbents and their removal capability was studied in detail. The obtained cellulose-based bioadsorbents interacted with different metal ions, exhibiting highly effective ion removal from aqueous solution at a wide pH range of 3.0–5.0. The maximum adsorption of Cr(III), Cu(II) and Co(II) was determined as 220.64, 213.49 and 137.55 mg/g, respectively, when the cellulose-based bioadsorbents were treated by 2000 mg/L metal solution at pH 3.0 for 14 h. Moreover, the competitive adsorption showed that cellulose-based bioadsorbents had higher adsorption selectivity for Cr(III) (54.72 mg/g) with the coexistence of Cu(II) and Co(II). The adsorption mechanisms were interpreted considering the functional groups of bioadsorbent, ion characteristics, and varitation of solution acidity. The higher adsorption of Cr(III) could be ascribed to the stronger attraction to the lone pair of electrons both in oxygen and nitrogen atom to form more stable complexes, while only carboxyl/carbonyl groups participated in the adsorption of Cu(II) and Co(II). These results are important because they provide not only a approach to structure-controlled adsorbent for pollutant removal, but also interesting information concerning the adsorption capability of these structures based on pore size and surface functional groups.

Cationic hyperbranched polyethylenimine (hPEI) was covalently linked onto the backbone of cellulose molecules via forming Schiff base structure between the amino groups of hPEI and the aldehyde groups on the chemically oxidized cellulose surface. The functionalized hPEI-CE possessed available active sites, and its adsorption behavior to anionic dye congo red (CR) and cationic basic yellow 28 (BY28) in aqueous solution was investigated. The hPEI-CE interacted with the two dyes, exhibiting sharp response to solution pH and ionic strength. The adsorption process was well dominated by the pseudo-second-order kinetic model. And the hPEI-CE following the Langmuir isotherm model, had a maximum adsorption capacity of 2100 mg g−1 for CR and 1860 mg g−1 for BY28, respectively. Further, the adsorption performance of six dyes onto the hPEI-CE was studied, which showed high adsorption capacities for CR, BY28, brilliant blue 133 (BB133), and reactive red, but very low adsorption for cationic bright yellow 7GL (7GL) and eosin Y (EY). The different adsorption performances for different dyes indicated the selective adsorption of the hPEI-CE for dyes owing to their different distribution coefficient (K) defining as the partition of dyes between hPEI-CE and water. Based on the unique selective adsorption, the mixtures of dyes, such as BB133-CR, BB133-BY28, BB133-7GL, and CR-7GL, were separated successfully using hPEI-CE.

In this paper, a facile and green method was presented to prepare flexible, ultralight, and hydrophobic cellulose aerogels (CA) on the chemical cross-linking of cellulose solution, lyophilization and subsequent hydrophobic modification with methyltrichlorosilane (MTCS) by a thermal chemical vapor deposition (CVD) process. The resultant cellulose aerogels had an interconnected and highly porous structure with a varied pore size owing to different starting solution concentrations. And also the cellulose aerogels were ultralight (as low as 0.027 g cm−3), but they exhibited improved mechanical properties with compress stress of 1.10–3.85 MPa. After silanization, the MTCS-modified cellulose aerogels showed durable hydrophobicity with an average water contact angle of 141°, even maintaining 131° after 5 days. Furthermore, the flexible and hydrophobic cellulose aerogels could rapidly collect oils and organic solvents both on the surface and bottom from water, and exhibited excellent adsorption performances (e.g. 59.32 g g−1 of pump oil) as well as good recyclability. Thus, such a flexible and hydrophobic cellulose aerogel is a very promising material for oil spill cleanup and industrial oily wastewater purification.

Robust, metal-free, macroscopic 3D porous g-C3N4/cellulose (CN/CE) hybrid photocatalyst was successfully fabricated by the co-assembly of g-C3N4 and cellulose substrate. The morphology, structure, mechanical property, optical and electrochemical performances, and photocatalytic activity of the CN/CE were investigated in detail. The obtained CN/CE hybrid photocatalyst possessed homogeneous 3D interconnected network structure, excellent mechanical strength and considerable recyclability. Also, the CN/CE hybrid photocatalyst exhibited both an excellent adsorption capacity and improved photocatalytic activity toward methylene blue (MB) degradation with degradation rate of 99.8%, much higher than that of pure g-C3N4 (54.2%). The enhanced photocatalytic performance of CN/CE derived from the synergistic effects of homogeneous 3D interconnected network structure and syncretic interfaces between g-C3N4 and cellulose, facilitating mass transport, light absorption and reactant adsorption, as well as the transfer of the photogenerated electrons. Moreover, the CN/CE hybrid photocatalyst indicated a high reusability and stability without significant reduction in its efficiency with nearly 96% of MB degradation after four cycles. This work not only demonstrated the importance of homogeneous interconnected network structure to prepare highly effective photocatalyst, but also provided a new insight into the approach for design and utilization of stable and recyclable metal-free photocatalyst for visible light derived contaminant degradation.