S.M. Sidik

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.

CO2 reforming of CH4 over Ni/mesostructured silica nanoparticles (Ni/MSN)

The development of supported Ni-based catalysts for CO2 reforming of CH4 was studied. Ni supported on mesostructured silica nanoparticles (MSN) and MCM-41 were successfully prepared using an in situ electrochemical method. The N2 physisorption results indicated that the introduction of Ni altered markedly the surface properties of MCM-41 and MSN. The TEM, H2-TPR and IR adsorbed CO studies suggested that most of the Ni deposited on the interparticles surface of MSN have higher reducibility than Ni plugged in the pores of MCM-41. Ni/MSN showed a higher conversion of CH4 at about 92.2% compared to 82.6% for Ni/MCM-41 at 750 °C. After 600 min of the reaction, Ni/MCM-41 started to deactivate due to the formation of shell-like carbon which may block the active sites and/or surface of catalyst, as proved by TEM analyses. Contrarily, the activity of Ni/MSN was sustained for 1800 min of the reaction. The high activity of Ni/MSN was resulted from the presence of greater number of easily reducible Ni on the surface. In addition, the large number of medium-basic sites in Ni/MSN was capable to avoid the formation of shell-like carbon that deactivated the catalyst, thus increased the stability performance. The results presented herein provide new perspectives on Ni-based catalysts, particularly in the potential of MSN as the support.

Nickel-promoted mesoporous ZSM5 for carbon monoxide methanation

Nickel-promoted mesoporous ZSM5 (Ni/mZSM5) was prepared for CO methanation. XRD, NMR and SEM analysis confirmed the structural stability of Ni/mZSM5 with coffin type morphology. The nitrogen physisorption and pyrrole adsorbed FTIR analyses indicated the presence of micro–mesoporosity and a moderate amount of basic sites on both mZSM5 and Ni/mZSM5. At 623 K, Ni/mZSM5 showed a high rate of CO conversion (141.6 μmol CO g-cat−1 s−1) and 92% CH4 yield. Ni/mZSM5 showed better catalytic performance than Ni/MSN (82.4 μmol CO g-cat−1 s−1, 82% CH4 yield), Ni/HZSM5 (29.0 μmol CO g-cat−1 s−1, 54.5% CH4 yield), and Ni/γ-Al2O3 (14.5 μmol CO g-cat−1 s−1, 38.6% CH4 yield). It is noteworthy that the superior catalytic performance of Ni/mZSM5 could be attributed to the presence of both micro–mesoporosity and basicity, which led to a synergistic effect of Ni metal active sites and the mZSM5 support. In situ FTIR spectroscopy showed that CO and H2 may be adsorbed on Ni metal followed by spillover to form adsorbed CO and adsorbed H on the mZSM5 surface. Then, two possible mechanisms for CO methanation were proposed. In the first mechanism, the adsorbed CO may be reacted with H2 to form CH4 and H2O. In the second mechanism, the adsorbed H may be reacted with CO to form CH4 and CO2. However, in this case, the former is the predominant pathway as the methanation reaction is favored by inhibition of the water–gas shift reaction.