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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.