Rafeah Wahi

Bio: Rafeah Wahi is an academic researcher from Universiti Malaysia Sarawak. The author has contributed to research in topics: Adsorption & Biochar. The author has an hindex of 11, co-authored 39 publications receiving 670 citations. Previous affiliations of Rafeah Wahi include Universiti Putra Malaysia.

Removal of Mercury, Lead and Copper from Aqueous Solution by Activated Carbon of Palm Oil Empty Fruit Bunch

Abstract: The ability of activated carbon prepared from palm oil empty fruit bunches (EFB) to remove mercury (Hg(II)), lead (Pb(II)) and copper (Cu(II)) from aqueous solutions was investigated. The EFB activated carbon was produced by using chemical and physical activation processes. The adsorption capacity was determined as a function of adsorbate initial concentration and adsorbent dosages. Adsorption isotherms of the studied metals on adsorbent were determined and compared with the Langmuir and Fruendlich isotherm models. The EFB activated carbon showed excellent efficiency in removing Pb(II) and Hg(II) with percentage of removal up to 100% even at low adsorbent dosage. In contrast, only 25% removal of Cu(II) by the EFB activated carbon was observed. The study also showed that the adsorption of Hg(II), Pb(II) and Cu(II) by EFB activated carbon is dependent on the dosage of adsorbent and the initial metals concentration. The use of EFB as activated carbon is not only effective for Hg(II) and Pb(II) removal from wastewater but also helps in solving the problem of over-abundance of EFB as agricultural waste product.

Activated Carbon for Catalyst Support from Microwave Pyrolysis of Orange Peel

Abstract: Orange peel, representing an abundant fruit waste in Asia, was transformed into activated carbon via the use of microwave pyrolysis. The orange peel was first subjected to microwave pyrolysis over a range of microwave power in order to produce an optimal yield of activated carbon as the target product. The activated carbon was extensively characterized for its porous characteristics, N2 adsorption and desorption isotherms, thermal stability, and chemical composition in order to assess its potential to be used as a catalyst-support material. Microwave pyrolysis of orange peel showed an approximately 70 wt% yield of activated carbon over the range of microwave power considered. The activated carbon was detected to have a high BET surface area associated with type I isotherm, which indicates the presence of microporous structure, thus exhibiting a characteristic of high adsorption capacity. The high adsorption capacity suggests that the activated carbon produced using this pyrolysis approach could act as an adsorbent to adsorb metal ions, therefore it shows great potential to be used as a catalyst-support material—the base material to which catalytically active substance such as metal binds to form a heterogeneous catalyst. The activated carbon also demonstrated high thermal stability in N2 atmospheres, representing a durable material to be synthesized into a catalyst for use in thermal process. Our results show that the activated carbon produced from microwave pyrolysis of orange peel shows exceptional promise as a catalyst-support material.

Chemically treated microwave-derived biochar: An overview

Abstract: Biochar, a carbon-rich material, can be produced via microwave pyrolysis, as a more energy and cost saving method compared to conventional externally heated pyrolysis. Biochar has versatile applications, for example, for soil amendment purpose and pollutant removal from wastewater. Chemical treatment has been proven to improve the physical and chemical properties of biochar for better applicability. Thus, extensive amount of research has been conducted on chemical treatment of conventional biochar, and several review articles have discussed published works on the chemically treated conventional biochar. However, there has been no review on works involving the chemically treated microwave-derived biochar, by far. This paper presents an overview of the current development and improvement on chemical treatment methods and applications of microwave-derived biochar.

Current state and future prospects of plastic waste as source of fuel: A review

Abstract: Due to the depleting fossil fuel sources such as crude oil, natural gas, and coal, the present rate of economic growth is unsustainable. Therefore, many sources of renewable energy have been exploited, but the potentials of some other sources such as plastics waste are yet to be fully developed as full scale economic activity. Development and modernization have brought about a huge increase in the production of all kinds of plastic commodities, which directly or indirectly generate waste due to their wide range of applications coupled with their versatility of types and relatively low cost. The current scenario of the plastic recycling technology is reviewed in this paper. The aim is to provide the reader with an in-depth analysis with respect to the pyrolysis of plastic waste as obtained in the current recycling technology. As the calorific value of the plastics is comparable to that of hydrocarbon fuel, production of fuel from plastic waste would provide a good opportunity to utilize the waste as a better alternative to dumpsites. Different techniques of converting plastics waste into fuel including thermal and catalytic pyrolysis, microwave-assisted pyrolysis and fluid catalytic cracking are discussed in detail. The co-pyrolysis of plastics waste with biomass is also highlighted. Thus, an attempt was made to address the problem of plastic waste disposal as a partial replacement of the depleting fossil fuel with the hope of promoting a sustainable environment.

Recent progress on catalytic pyrolysis of lignocellulosic biomass to high-grade bio-oil and bio-chemicals

Abstract: Pyrolysis converts lignocellulosic biomass to bio-oil that can be a precursor to fuel and chemicals for industries. The bio-oil contains high oxygenates fractions that deteriorate the bio-oil fuel properties. Catalysts acted to upgrade the bio-oil through selected bond cleavage reactions such as deoxygenation, cracking, decarbonylation and others reactions. Bulk and supported acid or base catalysts in biomass pyrolysis tailored the production of high-grade bio-oil. The catalytic biomass pyrolysis is an approach that is reliable for producing quality renewable fuel and chemical precursors. This paper elucidated recent studies on catalytic pyrolysis of lignocellulose biomass to renewable fuel grade bio-oil and chemicals. The review discussed the various principal activities on biomass characteristics and their potentials in pyrolysis process to produce the high-grade biofuel precursor. The possible processes used in perpetuating the pyrolysis devolatilisation of biomass are also appraised along with catalysts type, and their catalytic activities in the production of renewable bio-oil and bio-chemicals. Therefore, catalyst development for the upgrade of bio-oils from pyrolysis of biomass to renewable fuel and chemicals precursor remains a topical issue.