Artocarpus integer peel as a highly effective low-cost adsorbent for methylene blue removal: Kinetics, isotherm, thermodynamic and pelletized studies

Recently, there is a growing interest in identifying low-cost alternative adsorbents which have reasonable adsorption efficiency for dye removal. In this study, agricultural waste, Artocarpus Integer peel (AI-Peel) was used as the adsorbent to remove methylene blue (MB) from aqueous solution. The batch adsorption process was conducted to evaluate the effect of contact time (1 – 40 min), adsorbent dosage (0.25 – 4.0 g L-1), pH (2 – 8), initial dye concentration (100 – 500 mg L-1) and temperature (30 – 50 oC). The experimental data followed well pseudo-second-order kinetic model and Langmuir isotherm (Type 2) with maximum adsorption capacity of 396.825 mg g-1. The analysis of thermodynamic studies indicated that the adsorption process was exothermic, controlled by a chemisorption process, feasible and spontaneous in nature with decrease in degree of spontaneity at higher temperature. The characterization results revealed that the functional groups of AI-Peel play an important role in the adsorption of MB onto AI-Peel. The study of pelletized and reusability of AI-Peel indicated the great potential of pelletized AI-Peel as low-cost adsorbent for efficient removal of MB from aqueous solution. This study successfully discovers a new highly effective low-cost adsorbent for MB removal

Organic rankine cycle and steam turbine for intermediate temperature waste heat recovery in total site integration

The utilization of waste heat for heat recovery technologies in process sites has been widely known in improving the site energy saving and energy efficiency. The Total Site Heat Integration (TSHI) methodologies have been established over time to assist the integration of heat recovery technologies in process sites with a centralized utility system, which is also known as Total Site (TS). One of the earliest application of TSHI concept in waste heat recovery was through steam turbine using the popular Willan’s line approximation. The TSHI methodologies later were extended to integrate with wide range of heat recovery technologies in many literatures, whereby Organic Rankine Cycle (ORC) has been reported to be the one of the beneficial options for heat recovery. In general, the medium to high temperature waste heat is recovered via condensing/backpressure steam turbine, whereas ORC is targeted for recovering the low temperature waste heat. However, it is known that condensing turbine is also abled to generate power by condensing low grade steam to sub-ambient pressure, which is comparable with ORC integration. In this work, the integration of ORC and condensing turbine was considered for a multiple-process system to recover intermediate temperature waste heat through utility system. This study presented a numerical methodology to investigate the performance analysis of integration of ORC and condensing turbine in process sites for recovering waste heat from a centralized utility system. A modified retrofit case study was used to demonstrate the effectiveness application of the proposed methodology. The performances of ORC and condensing steam turbine were evaluated with the plant total utility costing as the objective function. The turbine integration was found to be more beneficial in the modified case study with lower utility cost involved. However, the capital cost has not been considered in the analysis

Photocatalytic degradation with green synthesized metal oxide nanoparticles – a mini review

Water pollution is one of the major problems faced by mankind worldwide. With the increase of populations and urbanization, the natural water resources are under great threat due to the release of untreated effluent. An alternative treatment method, photocatalysis, emerged as a promising solution. Photocatalysis process utilizes photosensitive catalyst to degrade the pollutant and one of the most common catalyst being used is metal oxide. To increase the photocatalytic activity, nanosized metal oxide being used instead of its bulk form. In these recent years, metal oxide nanoparticles production has been shifted towards a more environmentally friendly process which is also commonly known as green synthesis. In this review, we discussed on the photocatalytic process and production via green synthesis of common metal oxide nanoparticles being used as photocatalyst

Enhanced oxygen evolution reaction on polyethyleneimine functionalized graphene oxide in alkaline medium

Practical applications of metal free catalysts are hindered by their innate poor stability for electrocatalytic application. Accordingly, in this study, synthesis and functionalization of graphene oxide via a modified Tour's method (GOT) with different amine containing molecules results in excellent catalytic performance and stability toward OER in alkaline medium. The as-synthesized polyethyleneimine GOT electrode (P-GOT), produced current densities of 10, 50 and 100 mA/cm2 at overpotentials of 240, 350 and 420 mV, respectively, with small Tafel slope of 47 mV/dec. The X-ray diffraction analysis (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis confirms the successful functionalization of GOT by ethylenediamine (E) and polyethyleneimine (P) molecules, respectively. Morphological studies based on field emission scanning electron microscopy (FESEM) confirm that the modification via covalent bonding preserved the original wrinkled and layered structure of GOT. The P-GOT with cross-linked amine can expose more active sites and is not easy to peel off, which corresponds to attaining lower charge transfer resistance (1.01Ω cm2) and remarkable current stability in 1.0 M KOH solution, compared to the pristine GOT and E-GOT electrodes. From this perspective, our results therefore provide a valuable route for development and practical application of metal free catalytic materials for water oxidation reaction

Surface-modified fibrous membranes for fuel cell application

Low permeability layers of poly(1-vinylimidazole) were polymerised and deposited onto both sides of electrospun polyethersulfone (PES) nanofibrous sheet radiofrequency plasma. The layers not only act as an efficient fuel barrier layer but also impart high and stable proton conductivity, as well as better chemical and dimensional stabilities. Typically, the composite membrane exhibited methanol permeability as low as 33.20 x 10-8 cm2 s-1 and high through-plane proton conductivity of 52.4 mS cm-1 at 95% RH, indicating membrane selectivity of 0.675 x 108 mS.s cm-3, which is approximately 33 times greater than the selectivity of N115 under similar conditions

Fabrication of hydrophilic silica coating varnish on pineapple peel fiber based biocomposite

In the last several years, the interest on hydrophobic and hydrophilic solid subtract was increased due to many applications in daily life, agriculture and industry. The continuous effort has been made to fabricate suitable material with more efficient fabrication method. In this research, physical blending method have been used by mixing four components of modifying agent with organic beeswax varnish at different weight percentage. Those modifying agents consists of decamethylcyclopentasiloxane (D5), Silica nanoparticles (R812S), Polydimethylsiloxane (BP-9400) and non-ionic surfactant (Triton X-100) were mixed in the mass ratio of 52:3:34:1. The modified varnish produced was coated on Pineapple peel fiber (PAPF) biocomposite and were characterized using Water Contact Angle (WCA) instrument, Fourier Transform Infrared (FTIR) and Scanning Electron Microscope (SEM). Based on the wettability index analysis; the value of water contact angle was reduced when increasing weight percent of modifying agents from 101.87 to 22.98°. The morphology of the surface was observed to have more silica nanoparticles, along with the increasing concentration of modifying agent. It also supported by FTIR which shows the presence of Si-O peak at 1030.88 cm-1. These results proved that the modifying agent and organic beeswax varnish had successfully produced hydrophilic coated on the PAPF surface

Photocatalytic Degradation of Synthetic Sulfur Pollutants in Petroleum Fractions under Different pH and Photocatalyst

Thiophene is one of the sulfur compounds in the petroleum fraction that can be harmful to living things and lead to a critical effect on the ecosystem. Photocatalytic degradation is one of the promising methods in treating wastewater as it can mineralization of pollutants into carbon dioxide and water. Other than that, this method is non-toxic and relatively low cost. The production of hydroxyl radicals playing a vital role in the degradation of organic pollutants. It has been claimed that the usage of zinc oxide (ZnO) nanoparticles could give an excellent degradation process as this photocatalyst have high photosensitivity, low cost and chemically stable. However, the preparation method of ZnO nanoparticles will affect the agglomeration, particle size, shape and morphology of particles and lead to influence the photocatalytic activity in degrading thiophene. Therefore, this study focused on the effectiveness of ZnO nanoparticles in the presence of fibrous nanosilica (KCC-1) and polyethylene glycol (PEG) as the capping agent to degrade synthetic thiophene. ZnO/KCC-1 had been synthesized via the precipitation method and characterized by using Fourier Transform Infrared (FTIR). The chemical bond and nature of the photocatalyst from the FTIR results proved that the synthesis process to produce the ZnO/KCC-1 was succeed. The large surface area of KCC-1 increases the effectiveness of ZnO which is supported by the experimental data. Accordingly, the optimum condition for photocatalytic degradation of thiophene is under pH 7 by using ZnO/KCC-1 as photocatalyst. Hence, it is believed that this research could be implemented to remove the thiophene in petroleum fraction from the actual industrial effluents and this can preserve nature in the future

Electrosynthesis of zinc oxide-copper oxide supported on mesostructured silica nanoparticles for photocatalytic decolorization of methyl orange

Photodecolorization of dyes using heterogeneous catalyst is an important process in wastewater treatment. In this study, an electrochemical method was used to load zinc oxide and copper oxide onto mesostructured silica nanoparticles (CuO-ZnO/MSN). The catalysts were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy-energy dispersive X-ray (FESEM-EDX), transmission electron microscopy (TEM), nitrogen (N2) adsorption-desorption, Fourier transform infrared (FTIR), 29Si magic angle spin nuclear magnetic resonance (29Si MAS NMR), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis/DRS), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), photoluminescence (PL) and cyclic voltammetry (CV). The effects of Zinc (Zn) loading, alkaline treatment of MSN and Copper (Cu) loading were investigated for photocatalytic decolorization of methyl orange (MO) dye. Then, the optimization study was performed by response surface methodology (RSM) and the potential of the best synthesized catalyst was tested on decolorization of simulated dye wastewater. From the result, 5 wt% ZnO loaded on MSN (ZnO/MSN) showed the highest photodecolorization rate (9.93 × 10-2 h-1) compared to 1 and 10 wt% ZnO/MSN, due to good dispersion of ZnO on the MSN surface. The alkaline treatment of MSN to load 5 wt% of ZnO catalyst (ZM) of using ammonium hydroxide (NH4OH) (0.5-2.0 M) demonstrated that ZM prepared under 1.0 M NH4OH was the best catalyst that improved the photodecolorization rate up to 3.87 × 10-1 h-1. The formation of silicon-oxygen-zinc (Si-O-Zn) with new silicon-oxygen-silicon (Si-O-Si) bonds and creation of oxygen vacancies became the main factors that enhanced the photocatalytic performance. The introduction of Cu as a second metal (1, 3 and 5 wt%) onto ZM catalyst (C-ZM) showed the existence of a synergistic effect between both metal oxides by increasing the formation of Si-O-metal bonds, oxygen vacancies and lowering band gap energy. The high decolorization rate of MO was achieved (1.282 h-1), which resulted in 99.5 % of photodecolorization when using 1.0 g L-1 of 3 wt% CuO (3C-ZM) at pH 2 of MO solution. From the RSM experiments, a complete decolorization of MO was predicted (99.99 %) at the optimum conditions of pH 3.5 using 1.6 g L-1 of 4 wt% CuO (4C-ZM) catalyst. Lastly, the high decolorization of simulated dye wastewater (>75 %) using CuO-ZnO/MSN catalyst proved that the modifications of ZnO would have great significance in the synthesis and developing the various catalysts for wastewater treatment as well as for other applications

Effect of synthesis method on the photocatalytic performance of zinc oxide loaded on mesostructured silica nanoparticles

An advanced oxidation process (AOPs) using heterogeneous semiconductor photocatalysts such as TiO2, Fe2O3, ZnO, CuO, and ZrO2 have become a popular method for the removal of toxic pollutants from wastewater1,2. Among them, ZnO has been widely researched in photocatalytic applications due to its activity which is comparable to TiO2. Recently, the incorporation of ZnO into a mesoporous material support has been discussed by several research groups3,4. It is believed that the incorporation of both materials is a beneficial approach to improve the photocatalytic activity of the catalyst5,6. Therefore, in this study, two approaches have been introduced to prepare a zinc oxide loaded on mesostructured silica nanoparticles (ZnO/MSN) catalyst; in-situ (ZnO/MSNis) and impregnation (ZnO/MSNim). The effect of the preparation methods on the properties of both catalyst were studied via XRD and FTIR analysis. The introduction of zinc species onto silica framework was found to form an interaction between the host and support material. The desilication occurred in the silica framework of the MSN accompanied by isomorphous substitution of Zn2+cations to form an active species Zn–O–Si bond. The photocatalytic activity of both ZnO/MSNs were tested on photodecolorization of methyl orange (MO). The ZnO/MSNis showed the highest decolorization rate at an optimum dosage of 1 g L-1 using 3.06 × 10-2 mM MO after 8 h at pH 2 under UV irradiation. A kinetic study demonstrated that the photocatalytic reaction followed the pseudo first-order model