Aishah Abdul Jalil

Adsorption of methyl orange from aqueous solution onto calcined Lapindo volcanic mud

In this study, calcined Lapindo volcanic mud (LVM) was used as an adsorbent to remove an anionic dye, methyl orange (MO), from an aqueous solution by the batch adsorption technique. Various conditions were evaluated, including initial dye concentration, adsorbent dosage, contact time, solution pH, and temperature. The adsorption kinetics and equilibrium isotherms of the LVM were studied using pseudo-first-order and -second-order kinetic equations, as well as the Freundlich and Langmuir models. The experimental data obtained with LVM fits best to the Langmuir isotherm model and exhibited a maximum adsorption capacity (q(max)) of 333.3 mg g(-1); the data followed the second-order equation. The intraparticle diffusion studies revealed that the adsorption rates were not controlled only by the diffusion step. The thermodynamic parameters, such as the changes in enthalpy, entropy, and Gibbs free energy, showed that the adsorption is endothermic, random and spontaneous at high temperature. The results indicate that LVM adsorbs MO efficiently and could be utilized as a low-cost alternative adsorbent for the removal of anionic dyes in wastewater treatment.

CO2 methanation over heterogeneous catalysts: recent progress and future prospects

Catalytic approaches for CO2 fixation can play an important role, because CO2 can be artificially converted into reusable chemicals. Among the catalytic reactions of CO2, hydrogenation of CO2, the so-called methanation reaction, is a suitable technique for the fixation of CO2. This technique can be used to convert exhausted CO2 into methane (CH4), which can be recycled for use as a fuel or a chemical as well as by contributing to the reduction of CO2 emissions. Heterogeneous catalysts have been used to hydrogenate CO2 to methane. Heterogeneous catalysts are preferable to homogenous catalysts in terms of stability, separation, handling, and reuse, which reflects in lower costs for large-scale production. Significant progress has been made in this direction, the exploitation of novel heterogeneous catalysts. In this review, we discussed recent developments in this area, with emphases on catalytic reactivity and its physicochemical properties and reaction mechanism. Apart from materials aspects and catalytic performance, we also discuss fundamental strategies for the rational design of materials for effective transformation of CO2 to methane with the help of H2 and power sources.

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.

Amino modified mesostructured silica nanoparticles for efficient adsorption of methylene blue

In this work, mesostructured silica nanoparticles (MSN(AP)) with high adsorptivity were prepared by a modification with 3-aminopropyl triethoxysilane (APTES) as a pore expander. The performance of the MSN(AP) was tested by the adsorption of MB in a batch system under varying pH (2-11), adsorbent dosage (0.1-0.5 g L(-1)), and initial MB concentration (5-60 mg L(-1)). The best conditions were achieved at pH 7 when using 0.1 g L(-1) MSN(AP) and 60 mg L(-1)MB to give a maximum monolayer adsorption capacity of 500.1 mg g(-1) at 303 K. The equilibrium data were evaluated using the Langmuir, Freundlich, Temkin, and Harkins-Jura isotherms and fit well to the Freundlich isotherm model. The adsorption kinetics was best described by the pseudo-second order model. The results indicate the potential for a new use of mesostructured materials as an effective adsorbent for MB.

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.

Synthesis of dual type Fe species supported mesostructured silica nanoparticles: Synergistical effects in photocatalytic activity

Dual type Fe species (isomorphously substituted Fe species and a colloidal α-FeOOH (IS-FeOOH)) supported on mesostructured silica nanoparticles (IS-FeOOH/MSN) were prepared by a simple electrochemical method followed by impregnation. Characterization was conducted using X-ray diffraction, transmission electron microscopy, surface area analysis, Fourier-transform infrared spectroscopy, nuclear magnetic resonance, electron spin resonance, and X-ray photoelectron spectroscopy. The results suggested that silica removal occurred in the MSN framework to isomorphously substitute Fe cations while retaining the colloidal structure of IS-FeOOH. The catalytic activity of IS-FeOOH/MSN was tested on photo-Fenton-like degradation of 2-chlorophenol under fluorescent light irradiation. The performance of the catalyst was in the following order: 10 wt% IS-FeOOH/MSN > 15 wt% IS-FeOOH/MSN > 5 wt% IS-FeOOH/MSN > MSN, with removal percentages of 92.2, 79.3, 73.1, and 14.2%, respectively. The results suggest that a synergistic effect between the dual type of Fe species (Si–O–Fe and IS-FeOOH colloid) and MSN played important roles in enhancing the degradation. The results provide strong evidence to support the potential use of IS-FeOOH/MSN as a photo-Fenton-like nanocatalyst for organic pollutants treatment.

Influence of multi-walled carbon nanotubes on textural and adsorption characteristics of in situ synthesized mesostructured silica.

Carbon nanotubes-mesostructured silica nanoparticles (CNT-MSN) composites were prepared by a simple one step method with various loading of CNT. Their surface properties were characterized by XRD, N2 physisorption, TEM and FTIR, while the adsorption performance of the CNT-MSN composites were evaluated on the adsorption of methylene blue (MB) while varying the pH, adsorbent dosage, initial MB concentration, and temperature. The CNTs were found to improve the physicochemical properties of the MSN and led to an enhanced adsorptivity for MB. N2 physisorption measurements revealed the development of a bimodal pore structure that increased the pore size, pore volume and surface area. Accordingly, 0.05 g L(-1) CNT-MSN was able to adsorb 524 mg g(-1) (qm) of 60 mg L(-1) MB at pH 8 and 303 K. The equilibrium data were evaluated using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models, with the Langmuir model affording the best fit to the adsorption data. The adsorption kinetics were best described by the pseudo-first order model. These results indicate the potential of CNT-MSN composites as effective new adsorbents for dye adsorption.

Elucidation of acid strength effect on ibuprofen adsorption and release by aluminated mesoporous silica nanoparticles

Mesoporous silica nanoparticles (MSN) with 1–10 wt% loading of aluminum (Al) were prepared and characterized by XRD, N2 physisorption, 29Si and 27Al NMR, FT-IR and FT-IR preadsorbed pyridine. All samples were evaluated for ibuprofen adsorption and release. The results showed that MSN gave almost complete ibuprofen adsorption while the addition of 1, 5, and 10 wt% Al onto MSN (1Al-MSN, 5Al-MSN and 10Al-MSN) resulted in 35%, 58%, and 79% of adsorption, respectively. The characterization results elucidated that the highest adsorptivity of MSN was due to its highest surface silanol groups, while the increase in Bronsted acidity upon loading of Al provided more adsorption sites for the higher activity. Regardless of its highest adsorption capacity, MSN demonstrated the highest and fastest release (∼100%) in 10 h, followed by 1Al-MSN, 5Al-MSN and 10Al-MSN. The increase in Al loading increased the acid sites that hold the ibuprofen molecules, which raised the retention in ibuprofen release. The pKa of Si–OH–Al that is lower than Si–OH sites also attracted the ibuprofen more strongly, which resulted in the slower release of Al-MSN as compared to MSN. The cytotoxicity study exhibited that ibuprofen loaded Al-MSN was able to reduce the toxicity in the WRL-68 cells, verifying its ability to hold and slow the release of ibuprofen as well as minimize the risk of drug overdose.

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.

Acid-vacuo heat treated low cost banana stems fiber for efficient biosorption of Hg(II)

The potential of banana stem fiber (BSF) as a low cost biosorbent for Hg(II) removal was studied. HCl treatment increased the cellulose accessibility which led to an enhanced interaction of Hg(II) and BSF. Activation of BSF-HCl in vacuo at 373 K increased the maximum biosorption capacity from 28 to 372 mg g−1 and altered the activation energy from 3.5 to 76.9 kJ mol−1 showing an increase in Hg(II) chemisorption. FTIR and ESR results confirmed the large amount of structural defects on the activated BSF-HCl which led to the increase in Hg(II) uptake. Batch biosorption models showed that the kinetics follow pseudo-second-order and the equilibrium uptake fitted to all three-parameter models showing the Hg(II) biosorption behaves as a Langmuir isotherm. The non-linear regression method exhibited higher coefficient of determination values for isotherm and kinetic analyses compared to the linear method. The thermodynamic functions indicated that the nature of Hg(II) biosorption is an exothermic and non-spontaneous process.