Nur Farhana Jaafar

Utilization of bivalve shell-treated Zea mays L. (maize) husk leaf as a low-cost biosorbent for enhanced adsorption of malachite green

In this work, two low-cost wastes, bivalve shell (BS) and Zea mays L. husk leaf (ZHL), were investigated to adsorb malachite green (MG) from aqueous solutions. The ZHL was treated with calcined BS to give the BS-ZHL, and its ability to adsorb MG was compared with untreated ZHL, calcined BS and Ca(OH)(2)-treated ZHL under several different conditions: pH (2-8), adsorbent dosage (0.25-2.5 g L(-1)), contact time (10-30 min), initial MG concentration (10-200 mg L(-1)) and temperature (303-323 K). The equilibrium studies indicated that the experimental data were in agreement with the Langmuir isotherm model. The use of 2.5 g L(-1) BS-ZHL resulted in the nearly complete removal of 200 mg L(-1) of MG with a maximum adsorption capacity of 81.5 mg g(-1) after 30 min of contact time at pH 6 and 323 K. The results indicated that the BS-ZHL can be used to effectively remove MG from aqueous media.

Variation of the crystal growth of mesoporous silica nanoparticles and the evaluation to ibuprofen loading and release.

Mesoporous silica nanoparticles (MSNs) were synthesized with variable microwave power in the range of 100-450 W, and the resulting enhancement of MSN crystal growth was evaluated for the adsorption and release of ibuprofen. X-ray diffraction (XRD) revealed that the MSN prepared under the highest microwave power (MSN450) produced the most crystallized and prominent mesoporous structure. Enhancement of the crystal growth improved the hexagonal order and range of silica, which led to greater surface area, pore width and pore volume. MSN450 exhibited higher ibuprofen adsorption (98.3 mg/g), followed by MSN300(81.3 mg/g) and MSN100(74.1 mg/g), confirming that more crystallized MSN demonstrated higher adsorptivity toward ibuprofen. Significantly, MSN450 also contained more hydroxyl groups that provided more adsorption sites. In addition, MSN450 exhibited comparable ibuprofen adsorption with conventionally synthesized MSN, indicating the potential of microwave treatment in the synthesis of related porous materials. In vitro drug release was also investigated with simulated biological fluids and the kinetics was studied under different pH conditions. MSN450 showed the slowest release rate of ibuprofen, followed by MSN300 and MSN100. This was due to the wide pore diameter and longer range of silica order of the MSN450. Ibuprofen release from MSN450 at pH 5 and 7 was found to obey a zero-order kinetic model, while release at pH 2 followed the Kosmeyer-Peppas model.

New insights into self-modification of mesoporous titania nanoparticles for enhanced photoactivity: effect of microwave power density on formation of oxygen vacancies and Ti3+ defects

Mesoporous titania nanoparticles (MTN) were successfully prepared by a microwave (MW)-assisted method under various power densities. The catalysts were characterized by XRD, FT-IR, surface area analysis, TEM, and ESR. The characterization data indicated that higher power density increased the crystallinity and surface area of the MTN while decreasing the particle size and band-gap energy of the TiO2. Significantly, MW heating played an important role in formation of oxygen vacancies (OV) and Ti3+ site defects (TSD). The MTN (T1–T3) with 0.12, 0.37, and 0.56 W g−1 power density were found to degrade 84%, 88%, and 96% of 2-chlorophenol (2-CP) under visible light, respectively, compared to 69% by commercial TiO2. Besides narrowing the band gap, the OV and TSD also acted as electron acceptors that hindered the electron–hole recombination, as well as facilitated the charge carrier migration. The kinetics study over T3 showed that adsorption was the controlling step in the 2-CP degradation, which followed a pseudo-first-order Langmuir–Hinshelwood model. The photocatalytic reaction was still stable, even after five cycle runs without severe catalyst deactivation. This study demonstrates that the uniform heat distribution provided by MW is able to produce MTN that are rich with OV and TSD that are effective under visible light irradiation.

Synergistic interactions of Cu and N on surface altered amorphous TiO2 nanoparticles for enhanced photocatalytic oxidative desulfurization of dibenzothiophene

Amorphous TiO2 (AT) nanoparticles were prepared by a simple sol–gel method and subsequent incorporation with copper (5–20 wt%) via an electrochemical method in the presence of a supporting electrolyte, tetraethylammonium perchlorate (TEAP), was used to synthesize CuO/TiO2 (CAT) catalysts. The physicochemical properties of the catalysts were studied by XRD, N2 adsorption–desorption, TEM, FTIR, XPS, ESR and UV-Vis DRS. Photocatalytic testing on the oxidative desulfurization of dibenzothiophene (DBT) under UV and visible light irradiation demonstrated that the CAT catalysts were active under both conditions. It was found that Ti3+ surface defects (TSD), oxygen vacancies (Vo), CuO, Ti–O–N/O–Ti–N and Ti–O–Cu bonds played an important role in photooxidation. The TSD, Vo, CuO, N 1s and Cu 2p states in the CAT catalysts acted as electron trappers to hinder electron–hole recombination. In addition, these TSD, Vo, N 1s and Cu 2p species also contributed to the lowering of the CAT band gap, which enabled photooxidation to be carried out in the visible light region. The photooxidation followed a pseudo-first order Langmuir–Hinshelwood model with adsorption being the controlling step.

Copper oxide supported on graphene for phodegradation of rhodamine B

In recent years, dyes are one of the major sources of the water contamination that lead to environmental problems. For instance, Rhodamine B (RhB) which was extensively used as a colorant in textile industries is toxic and carcinogenic. Among many techniques, photocatalytic degradation become the promising one to remove those dyes from industrial wastewater. Recently, graphene has shown outstanding performance in this application due to its intrinsic electron delocalisation which promotes electron transport between composite photocatalyst and pollutant molecules. While, copper oxide (CuO) is well-known has a lower bandgap energies compared to other semiconductors. Therefore, in this study, copper oxide supported on graphene (CuO/G) was prepared and its photocatalytic activity was tested on degradation of RhB. The catalysts were characterized by X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) Spectroscopy. The results showed that the interaction between copper and graphene support could enhance the photocatalytic activity. The 5 wt% CuO/G was found to give the highest degradation (95%) of 10 mg L -1 of RhB solution at pH 7 using 1 g L -1 catalyst after 4 hours under visible light irradiation. The photodegradation followed the pseudo first-order Langmuir-Hinshelwood kinetic model. This study demonstrated that the CuO/G has a potential to be used in photocatalytic degradation of various organic pollutants.