Biological, chemical and mathematical sciences

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Browsing Biological, chemical and mathematical sciences by Subject "Agricultural wastes—Recycling—Research"

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    Adsorption of lead (II) from aqueous solution using nano-papaya peel
    (Universiti Teknologi Malaysia, 2017) Abbaszadeh, Sahar
    The presence of toxic heavy metals like lead (Pb(II)) in water resources due to industrialization is known to be a major environmental concern in many communities. Agrowaste has been the focus of studies as a reliable source of sustainable adsorbents for heavy metal removal from aqueous solutions. In this study, papaya peel has been introduced as a new source of agro-waste. The high annual papaya production in Malaysia potentially provides a good base to use its waste to develop an inexpensive adsorbent. Most of previous studies only consider the raw or carbon-active form of bioadsorbents. The present study aims to develop potential adsorption media for the removal of Pb(II) from contaminated water. While raw and carbon-activated adsorbents from papaya peel agro-waste are considered, a new nano adsorbent has been developed and evaluated in this research. The equilibrium sorptions of Pb(II) from an aqueous solution using synthesized adsorbents of activated carbon papaya peel (AC-PP) and nano-papaya peel (Nano-PP) were investigated. The synthesized adsorbents were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, field emission scanning electron microscopy, x-ray diffractometery and x-ray photoelectron spectroscopy. The batch experiments were carried out considering various Pb(II) concentrations of 10, 20, 50, 100, 200, and 400 mg/L, by changing variables of pH, adsorbent dosage, initial metal concentration, and temperature and contact time. The removal efficiency of the adsorbed amount of metal ions was considered relative to the equilibrium parameters. Desorption and regeneration studies were additionally conducted to evaluate reusability. The developed adsorbents showed excellent performance. Pb(II) was removed after 2 h of agitation, reaching optimal removal percentages of 82.6% using AC-PP (100 mg dosage) and 99.39 % using Nano-PP (50 mg dosage) after 3 h, at pH=5, in ambient condition. Equilibrium adsorption isotherms and kinetics were reviewed using the different isotherm models of Langmuir, Freundlich, and Temkin and kinetic models of the pseudo-first order, pseudo-second order, and intra-particle diffusion. The adsorption processes of Pb(II) onto Nano-PP and AC-PP were better described by the Langmuir isotherm model indicating monolayer Pb(II) adsorption onto the surface of the developed adsorbents and the adsorption kinetics was well fitted with the pseudo second-order kinetic model. Additionally, thermodynamic results confirmed the spontaneous adsorption processes with exothermic and endothermic nature onto surface of AC-PP and Nano-PP, respectively. The results obtained, especially for Nano-PP, confirm the capability of papaya peel adsorbents as a new, low-cost, efficient and environmentally friendly alternative for Pb(II) removal from contaminated water.
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    Succinic acid production via simultaneous saccharification and fermentation of oil palm empty fruit bunch
    (Universiti Teknologi Malaysia, 2017) Akhtar, Junaid
    Oil palm empty fruit bunch (EFB), a plentiful agricultural waste in Malaysia has never been utilized for the production of succinic acid via simultaneous saccharification and fermentation (SSF). The presence of lignin and hemicellulose makes the biomass difficult to be hydrolysed by enzymes and microbes. Hence, effective pretreatment method is required to release cellulose from the crystalline complex structure of lignocellulose. The novelty of this study is the production of succinic acid via SSF from EFB by a rumen bacteria Actinobaccilus succinogenes ATCC 55618. The effect of three different methods; autoclave/alkali (AA), dilute acid (DA) and sequential dilute acid microwave/alkali (DA-MwA) pretreatment on the physical and chemical properties of EFB were analysed and their influence on enzymatic hydrolysis and SSF process were also assessed. Results revealed that maximum amount of cellulose (86.8 g/100g) was achieved for DA-MwA as compared with AA (53.3 g/100g) and DA (46.7 g/100g). The highest glucose concentration among all pretreated EFB was DA-MwA (20.3 gL-1) method using cellulase enzyme. The effect of different cellulase: cellobiase ratios on enzymatic hydrolysis of DA-MwA pretreated EFB showed that ratio of 7:1 produced 34.45 % higher glucose as compared when only cellulase was used. Succinic acid concentration via SSF from DA-MwA (33.4 gL-1) was the highest followed by AA (20.9 gL-1) and DA (14.4 gL-1). The SSF media for the succinic acid production was optimized using Full Factorial Design (FFD) by varying the EFB loading (10-70 gL-1 ), yeast extract (0-20 gL-1) and corn steep liquor (0-20 gL-1) followed by Face Central Composite Design. The best concentration of succinic acid (39.14 gL-1) was obtained when the values of EFB, yeast extract and corn steep liquor were set at 70 gL-1, 30 gL-1 and 10 gL-1, respectively. The influence of three independent SSF process variables: enzyme loading (10-70 FPU/g), temperature (36-40 °C) and pH (5-8) were investigated for succinic acid production using FFD. When the enzyme loading was set at 40 FPU/g, temperature 36 °C and pH 5; the experimental values were in good agreement with the predicted Response Surface Methodology model where the best succinic acid production of 42.5 gL-1 was achieved. The present study revealed that using DA-MwA pretreated EFB, cellulose was utilized by cellulase and cellobiase enzymes via optimized SSF conditions resulting in optimum production of succinic acid.