Zahra Gholami

Application of chitosan and its derivatives as adsorbents for dye removal from water and wastewater: a review.

Chitosan based adsorbents have received a lot of attention for adsorption of dyes. Various modifications of this polysaccharide have been investigated to improve the adsorption properties as well as mechanical and physical characteristics of chitosan. This review paper discusses major research topics related to chitosan and its derivatives for application in the removal of dyes from water. Modification of chitosan changes the original properties of this material so that it can be more suitable for adsorption of different types of dye. Many chitosan derivatives have been obtained through chemical and physical modifications of raw chitosan that include cross-linking, grafting and impregnation of the chitosan backbone. Better understanding of these varieties and their affinity toward different types of dye can help future research to be properly oriented to address knowledge gaps in this area. This review provides better opportunity for researchers to better explore the potential of chitosan-derived adsorbents for removal of a great variety of dyes.

Chitosan hydrogel beads impregnated with hexadecylamine for improved reactive blue 4 adsorption

Adsorption performance of chitosan (CS) hydrogel beads was investigated after impregnation of CS with hexadecylamine (HDA) as a cationic surfactant, for the elimination of reactive blue 4 (RB4) from wastewater. The CS/HDA beads formed with 3.8% HDA were the most effective adsorbent. The adsorption capacity was increased by 1.43 times from 317 mg/g (CS) to 454 mg/g (CS/HDA). The RB4 removal increased with decrease in the pH of dye solution from 4 to 9. The isotherm data obtained from RB4 adsorption on CS and CS/HDA are adequately described by Freundlich model (R(2)=0.946 and 0.934, χ(2)=22.414 and 64.761). The kinetic study revealed that the pseudo-second-order rate model (R(2)=0.996 and 0.997) was in better agreement with the experimental data. The negative values of ΔG° (-2.28 and -6.30 kJ/mol) and ΔH° (-172.18 and -101.62 kJ/mol) for CS beads and HDA modified CS beads, respectively; suggested a spontaneous and exothermic process for RB4 adsorption.

A review on composting of oil palm biomass.

Abstract Nowadays, the biomass produced in oil palm industry, such as oil palm fronds, palm pressed fibers, palm kernel shells, empty fruit bunch, and liquid waste discharged from the palm oil mill effluent and others, may lead to significant environmental concerns. The quantity of produced wastes by oil palm industry is increasing with the growth of this industry day by day. Therefore, the use of these wastes as compost is considered by researchers to overcome their negative impacts and recycle them to produce a useful byproduct for agriculture. This review analyzes the recent composting studies on palm oil biomass and provides useful information about the potential uses of these biomass in composting as an alternative method for enhanced and sustainable use of biomass produced from oil palm industry. In addition, environmental impacts of composting are discussed. This knowledge could build a platform for researchers in this area to understand the recent developments in palm oil biomass composting by means of addressing the environmental pollution concerns as well.

Oil Palm Biomass as an Adsorbent for Heavy Metals

Many industries discharge untreated wastewater into the environment. Heavy metals from many industrial processes end up as hazardous pollutants of wastewaters.Heavy metal pollution has increased in recent decades and there is a growing concern for the public health risk they may pose. To remove heavy metal ions from polluted waste streams, adsorption processes are among the most common and effective treatment methods. The adsorbents that are used to remove heavy metal ions from aqueous media have both advantages and disadvantages. Cost and effectiveness are two of the most prominent criteria for choosing adsorbents. Because cost is so important, great effort has been extended to study and find effective lower cost adsorbents.One class of adsorbents that is gaining considerable attention is agricultural wastes. Among many alternatives, palm oil biomasses have shown promise as effective adsorbents for removing heavy metals from wastewater. The palm oil industry has rapidly expanded in recent years, and a large amount of palm oil biomass is available. This biomass is a low-cost agricultural waste that exhibits, either in its raw form or after being processed, the potential for eliminating heavy metal ions from wastewater. In this article, we provide background information on oil palm biomass and describe studies that indicate its potential as an alternative adsorbent for removing heavy metal ions from wastewater. From having reviewed the cogent literature on this topic we are encouraged that low-cost oil-palm-related adsorbents have already demonstrated outstanding removal capabilities for various pollutants.Because cost is so important to those who choose to clean waste streams by using adsorbents, the use of cheap sources of unconventional adsorbents is increasingly being investigated. An adsorbent is considered to be inexpensive when it is readily available, is environmentally friendly, is cost-effective and be effectively used in economical processes. The advantages that oil palm biomass has includes the following:available and exists in abundance, appears to be effective technically, and can be integrated into existing processes. Despite these advantages, oil palm biomasses have disadvantages such as low adsorption capacity, increased COD, BOD and TOC. These disadvantages can be overcome by modifying the biomass either chemically or thermally. Such modification creates a charged surface and increases the heavy metal ion binding capacity of the adsorbent.

Selective Monolaurin Synthesis through Esterification of Glycerol Using Sulfated Zirconia-Loaded SBA-15 Catalyst

The selective conversion of lauric acid to glycerol monolaurin over sulfated zirconia SBA prepared under various conditions was investigated in this study. The structural properties of the prepared catalysts were characterized using different characterization techniques. Sulfated zirconia was successfully incorporated with improved properties, such as larger mesopore surface area; the mesoporous structure was preserved as well. The highest yield of 79.1% was obtained during reaction over SZSBA-15 catalyst with 16 wt.% zirconium oxychloride loading and 3 h of reflux time. About 83.4% selectivity toward monolaurin was achieved at a high conversion of lauric acid (94.9%), a lauric acid-to-glycerol molar ratio of 4.0, within 6 h, and at 160°C. Product distribution was successfully elucidated. High selectivity to monolaurin was influenced by molecular sieving effects.

Catalytic Etherification of Glycerol to Diglycerol Over Heterogeneous Calcium-Based Mixed-Oxide Catalyst: Reusability and Stability

The activities of different heterogeneous alkaline-earth metal oxide catalysts and mixed-metal oxide catalysts were investigated. Glycerol etherification was carried out at 250°C in a three-necked glass reactor vessel at atmospheric pressure. In a typical experiment, 50 g of anhydrous glycerol was loaded into the reactor. Then, 2 wt.% of catalyst was added to the reactor. The reactor was then heated to the appropriate reaction temperature in nitrogen atmosphere under continuous stirring. The heterogeneous CaO catalyst showed the highest catalytic conversion (72%) compared with other alkaline-earth metal oxides, with a diglycerol yield of 19%. The highest glycerol conversion of 96% and diglycerol yield of 52% were observed for the mixed-metal oxide catalyst (Ca1.6Al0.4La0.6O3). Reusability and stability of this catalyst were tested. The ICP-AES analysis was performed to confirm the leaching of the metal species in the liquid phase of the reaction mixture.

The influence of catalyst factors for sustainable production of hydrocarbons via Fischer-Tropsch synthesis

Abstract Fischer-Tropsch synthesis (FTS) is a process which catalytically converts syngas (H2 and CO) into clean hydrocarbon fuels. Syngas can be derived from non-petroleum feed stocks such as coal, natural gas or biomass. Increasing the quality of products by development of novel catalysts with high activity and selectivity is desirable in FTS reaction. This article reviews and summarizes recent developments in FTS catalysts and the effects of key factors such as active metals, catalyst supports and promoters on feedstock conversion and product selectivities.

Synthesis and characterization of niobium-promoted cobalt/iron catalysts supported on carbon nanotubes for the hydrogenation of carbon monoxide

Abstract Bimetallic Co/Fe catalysts supported on carbon nanotubes (CNTs) were prepared, and niobium (Nb) was added as promoter to the 70Co:30Fe/CNT catalyst. The physicochemical properties of the catalysts were characterized, and the catalytic performances were analyzed at the same operation conditions (H2:CO (volume ratio) = 2:1, p = 1 MPa, and t = 260°C) in a tubular fixed-bed microreactor system. The addition of Nb to the bimetallic catalyst decreases the average size of the oxide nanoparticles and improves the reducibility of the bimetallic catalyst. Evaluation of the catalyst performance in a Fischer-Tropsch reaction shows that the catalyst results in high selectivity to methane, and the selectivity to C5+ increased slightly in the bimetallic catalyst unlike that in the monometallic catalysts. The addition of 1% Nb to the bimetallic catalyst increases CO conversion and selectivity to C5+. Meanwhile, a decrease in methane selectivity is observed.

Comparison of preparation techniques for CoFeNb/CNTs catalyst

CoFe-based catalysts were prepared using reverse-microemulsion and co-impregnation method. Effect of different preparation techniques on morphology and physiochemical properties of the FTS catalyst CoFeNb/CNTs was investigated. TEM analyses show that the morphological properties of catalysts were affected by preparation techniques. Reverse-micremulsion and co-impregnation method resulted in average particle size of 5.61 nm and 6.20 nm respectively. CoFe-impregnation catalyst is reducible at lower temperature compared to that of reverse-microemulsion catalyst. Acid and thermal treatment of CNTs created defects onto CNTs-support.

Modified silica-based heterogeneous catalysts for etherification of glycerol

The advent of mesoporous silicas such as MCM-41 has provided new opportunities for research into supported metal catalysis. The loading of metals into framework structures and particularly into the pores of porous molecular sieves, has long been of interest because of their potential catalytic activity. Stable heterogeneous mesoporous basic catalysts were synthesized by wet impregnation of MCM-41 with calcium nitrate and lanthanum nitrate. The surface and structural properties of the prepared catalysts were characterized using BET surface analysis, SEM and TEM. MCM-41 and modified MCM-41 were used in the solventless etherification of glycerol to produce diglycerol as the desired product. The reaction was performed at 250 °C for 8 h, and catalyst activity was evaluated. Catalytic etherification over the 20%Ca1.6La0.6/MCM-41 catalyst resulted in the highest glycerol conversion of 91% and diglycerol yield of 43%.