Enhanced Adsorption of Methylene Blue by Chemically Modified Materials Derived from Phragmites australis Stems.

In this study, the biomass of Phragmites australis was chemically modified using NaOH and subsequently citric acid to produce an effective adsorbent named SA-RPB. The absorbent was characterized using XRD, SEM, BET, and FT-IR methods. The study's findings indicated that the adsorbent existed mainly as cellulose crystals, contained micropores with an average diameter of 15.97 nm, and had a large number of hydroxyl and carboxyl groups on the surface. The adsorption process of SA-RPB was evaluated through the adsorption of methylene blue (MB) dye in aqueous solution. Adsorption kinetics showed that the pseudo-second-order model well described the adsorption process. The adsorption isotherm process satisfactorily fitted with the Langmuir model with the maximum adsorption capacity of 191.49 mg/g at 303 K. These findings show that MB may be efficiently removed from aqueous solutions using the adsorbent made from the raw biomass of Phragmites australis treated with NaOH and then citric acid.

Facile fabrication of highly flexible and floatable Cu2O/rGO on Vietnamese traditional paper toward high-performance solar-light-driven photocatalytic degradation of ciprofloxacin antibiotic.

In this work, we successfully demonstrated the facile fabrication of highly flexible and floatable Cu2O/rGO on Vietnamese traditional paper (VTP) for the solar-light-driven photocatalytic degradation of the antibiotic ciprofloxacin. The catalyst membrane was prepared by the green reduction of both Cu(OH)2 to Cu2O nanoparticles and graphene oxide to reduced graphene oxide. VTP has a fibrous structure with tiny fibers connected like a spider web and multiple layers in the form of a multidimensional array, which functions as a flexible and highly porous supporter to the catalyst. Moreover, the microfibrillated cellulose of VTP acts as micro-capillaries to drag ciprofloxacin (CIP) close to the active sites on the Cu2O/rGO/VTP surface, which improves the adsorption capacity and photocatalytic efficiency of ciprofloxacin. The adsorption process is best described by the pseudo-first-order and Freundlich models. The maximum photodegradation of CIP by the catalyst is more than 80% attained after 1.5 h under solar light irradiation with a fixed CIP concentration of 10 mg L-1. The catalyst membrane exhibited good reusability of up to 5 cycles.

Unraveling the effect of Al doping on CO adsorption at ZnO(101̄0).

Understanding the effect of Al doping on CO adsorption at ZnO(101̄0) is crucial for designing a high-performance CO gas sensor. In this work, we investigated the adsorption properties of CO on pristine and Al-doped ZnO(101̄0) by performing DFT+U calculations. It is found that the doping of Al on ZnO(101̄0) induces the semiconductor-to-metal transition and thus enhances the conductance of the substrate. Compared to the pristine ZnO(101̄0), the adsorption energy of CO on the Al-doped surfaces is significantly enhanced since Al doping has the effect of strengthening the adsorption bond. The bonding analysis reveals that CO adsorbs on pristine ZnO(101̄0) via the sole σ-dative donation between the CO HOMO 5σ and the empty states of the Zn cation while π-back donation from filled states of Zn or Al cations to the CO 2π* LUMO is facilitated on the Al-doped surfaces. The π-back donation also results in the red-shift of the CO stretching frequency on the Al-doped surfaces, contrasting to the blue-shift on the pristine surface. The simulated results demonstrate that the doping of Al to a three-fold coordinated site on ZnO(101̄0) is highly beneficial for boosting the performance of the CO gas sensor. Our theoretical investigation provides fundamental insights into the effect of Al doping on the sensing mechanism for CO at the ZnO(101̄0) surface.