The goal of this work is to improve the simultaneous removal of Pb2+, Cu2+, Zn2+, and Cd2+ ions from synthetic wastewater in a fixed bed column by incorporating sodium dodecyl sulfate (SDS) onto the surface of activat...The goal of this work is to improve the simultaneous removal of Pb2+, Cu2+, Zn2+, and Cd2+ ions from synthetic wastewater in a fixed bed column by incorporating sodium dodecyl sulfate (SDS) onto the surface of activated carbon made from coconut shells. The activated carbons were characterized using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy-energy dispersive x-ray (SEM-EDX). The adsorption column dynamics were studied by varying the flow rates (5, 10 and 15 mL/min), bed heights (10, 15 and 20 cm), and initial concentrations (50, 150, and 250 mg/L). The activated carbon has a pore volume of 0.715 cm3/g and a BET-specific surface area of 1410 m2/g. Sodium dodecyl sulfate (SDS) surfactant incorporation onto the surface of the activated carbon enhances its capacity for simultaneous adsorption of Pb2+, Cu2+, Zn2+, and Cd2+ from the aqueous medium. The affinity of the heavy metals to both unmodified (AC) and modified (AC-SDS) activated carbons followed the order of Pb2+ > Cu2+ > Zn2+ > Cd2+. The dynamic adsorption of the column depends on the flow rate, bed height, initial metal concentration, and SDS surface modification. With a 5 mL/min flow rate, a 20 cm bed height, and a 50 mg/L initial metal concentration, a maximum break-through time of 150 minutes for the unmodified activated carbon (AC) and 180 minutes for the SDS-modified activated carbon (AC-SDS) was reached.展开更多
This article reports a high yielding technique of synthesizing zirconium dodecyl sulphate (“ZDS”) for in situ transesterification of Nannochloropsis occulata and Chlorella vulgaris for fatty acid methyl ester (FAME)...This article reports a high yielding technique of synthesizing zirconium dodecyl sulphate (“ZDS”) for in situ transesterification of Nannochloropsis occulata and Chlorella vulgaris for fatty acid methyl ester (FAME) production. ZDS produced a significantly higher FAME yield in N. occulata than in C. vulgaris (p = 0.008). The varying performance of ZDS in the two species could be due to their different cell wall chemistries. Sodium dodecyl sulphate (SDS) in H2SO4 for FAME enhancement from the two species was also studied. Treatment with SDS in H2SO4 increased the FAME production rate in both species. Residual protein content after the in situ transesterification in C. vulgaris and N. occulata reduced respectively by 6.5% and 10%. The carbohydrate content was reduced by 71% in C. vulgaris and 65% in N. occulata. The water tolerance of the process when using H2SO4, with or without SDS, was evaluated by hydrating the two species with 10% - 30% distilled water (w/w dry algae). The FAME concentration began to diminish only at 30% water content in both species. Furthermore, the presence of a small amount of water in the biomass or methanol increased the lipid extraction efficiency, improving the FAME yield, rather than inhibiting the reaction.展开更多
Effluents containing inorganic contaminants are releasing into the environment untreated despite being hazardous to man and environment. It is costly and unsustainable to use conventional methods to remove them from d...Effluents containing inorganic contaminants are releasing into the environment untreated despite being hazardous to man and environment. It is costly and unsustainable to use conventional methods to remove them from dilute aqueous solution. Adsorption involving granular activated carbon is an alternative method for treating such effluents. Granular activated carbon is structurally strong, highly resistance to attrition and wearing, large and can easily separate from the effluents. However, its surface is highly hydrophobic and has little surface charge thereby reducing its adsorption capacity for anion or cation. This article reviews surfactant modification of activated carbon to enhance its adsorption capacity for inorganic contaminants and key factors affecting the adsorption efficiency. They include initial concentration of contaminants, contact time, solution pH, solution temperature, adsorbent concentration, ionic strength, competing ions, type of surfactant, and surfactant concentration. The modified activated carbon usually shows maximum contaminant uptake around its critical micelles concentration. Surfactant modification reduces specific surface area and/or micro pore volume but hot NaOH or HNO3 treatment before surfactant modification minimises this drawbacks and increases the net surface charge. Overall, surfactant modification is a simple but efficient method of enhancing adsorption capacity of activated carbon for removing anion or cation from aqueous solution. However, a handful publication is available on the regeneration of the spent (saturated) surfactant modified activated carbons. Hence, more research efforts should be directed towards proper regenerating reagents and the optimise conditions such as contact time, concentration, and temperature for regenerating spent modified activated carbons.展开更多
Common ways of disposing waste plastic such as incineration and landfilling have negative impacts on the environment. Partial replacement of natural aggregate in concrete with waste plastic including polyethylene tere...Common ways of disposing waste plastic such as incineration and landfilling have negative impacts on the environment. Partial replacement of natural aggregate in concrete with waste plastic including polyethylene terephthalate (PET) is more environmental friendly and sustainable. The effect of adding 5% to 20% waste plastic by volume of natural coarse aggregate (“gravel”) and plastic particle size (3 to 7 mm) on the density and compressive strength of plastic-concrete mix after 28 days of curing was studied. The results showed that density of the concrete decreased from 2406.7 to 2286.7 kg/m3 as waste plastic increased from 5% to 20% v/v compared with 2443.3 kg/m3 recorded by concrete without waste plastic. Change in particle size from 3 to 7 mm has no significant effect on the density of the plastic-concrete mix. The compressive strength decreased as the volume and particle size of waste plastic increased. When waste plastic volume changed from 5% to 20% v/v, the compressive strength decreased from 20.5 to 15 MPa, 18.6 to 14.3 MPa and 17.2 to 13.8 MPa for 3, 5 and 7 mm waste plastic particle size respectively while the concrete without plastic has 21.33 MPa. Therefore, the addition of 5% (v/v gravel) of flaky waste plastic in the concrete produces a lightweight concrete which could offer economic benefit without substantially reducing the compressive strength of the plastic-concrete mix.展开更多
Microalgal phospholipid bilayer contributes to the molar excesses of methanol and high acid concentration required in reactive extraction to achieve high fatty acid methyl ester (FAME) yield. This study reports an inv...Microalgal phospholipid bilayer contributes to the molar excesses of methanol and high acid concentration required in reactive extraction to achieve high fatty acid methyl ester (FAME) yield. This study reports an investigation into the effects of pre-soaking Nannochloropsis occulata in methanol at 600:1 and 1000:1 methanol to oil molar ratios prior to acid-catalyzed in situ transesterification at 8.5:1 and 15:1 H2SO4 to oil molar ratios on the FAME yield. The results showed that the pre-soaked Nannochloropsis occulata produced a higher FAME yield at the two tested methanol to oil molar ratios and acid concentrations than the un-soaked, resulting in a reduction in methanol volume and acid concentration. A maximum FAME yield of 98.4% ± 1.3% was obtained for the pre-soaked Nannochloropsis occulata at 1000:1 methanol to oil molar ratio and 15:1 H2SO4 to oil molar ratio. Both the phosphorus mass balance and conversion of the isolated phospholipids into FAME revealed that pre-soaking solubilizes the phospholipid bilayer to some degree, and contributes to an increased FAME yield.展开更多
文摘The goal of this work is to improve the simultaneous removal of Pb2+, Cu2+, Zn2+, and Cd2+ ions from synthetic wastewater in a fixed bed column by incorporating sodium dodecyl sulfate (SDS) onto the surface of activated carbon made from coconut shells. The activated carbons were characterized using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy-energy dispersive x-ray (SEM-EDX). The adsorption column dynamics were studied by varying the flow rates (5, 10 and 15 mL/min), bed heights (10, 15 and 20 cm), and initial concentrations (50, 150, and 250 mg/L). The activated carbon has a pore volume of 0.715 cm3/g and a BET-specific surface area of 1410 m2/g. Sodium dodecyl sulfate (SDS) surfactant incorporation onto the surface of the activated carbon enhances its capacity for simultaneous adsorption of Pb2+, Cu2+, Zn2+, and Cd2+ from the aqueous medium. The affinity of the heavy metals to both unmodified (AC) and modified (AC-SDS) activated carbons followed the order of Pb2+ > Cu2+ > Zn2+ > Cd2+. The dynamic adsorption of the column depends on the flow rate, bed height, initial metal concentration, and SDS surface modification. With a 5 mL/min flow rate, a 20 cm bed height, and a 50 mg/L initial metal concentration, a maximum break-through time of 150 minutes for the unmodified activated carbon (AC) and 180 minutes for the SDS-modified activated carbon (AC-SDS) was reached.
文摘This article reports a high yielding technique of synthesizing zirconium dodecyl sulphate (“ZDS”) for in situ transesterification of Nannochloropsis occulata and Chlorella vulgaris for fatty acid methyl ester (FAME) production. ZDS produced a significantly higher FAME yield in N. occulata than in C. vulgaris (p = 0.008). The varying performance of ZDS in the two species could be due to their different cell wall chemistries. Sodium dodecyl sulphate (SDS) in H2SO4 for FAME enhancement from the two species was also studied. Treatment with SDS in H2SO4 increased the FAME production rate in both species. Residual protein content after the in situ transesterification in C. vulgaris and N. occulata reduced respectively by 6.5% and 10%. The carbohydrate content was reduced by 71% in C. vulgaris and 65% in N. occulata. The water tolerance of the process when using H2SO4, with or without SDS, was evaluated by hydrating the two species with 10% - 30% distilled water (w/w dry algae). The FAME concentration began to diminish only at 30% water content in both species. Furthermore, the presence of a small amount of water in the biomass or methanol increased the lipid extraction efficiency, improving the FAME yield, rather than inhibiting the reaction.
文摘Effluents containing inorganic contaminants are releasing into the environment untreated despite being hazardous to man and environment. It is costly and unsustainable to use conventional methods to remove them from dilute aqueous solution. Adsorption involving granular activated carbon is an alternative method for treating such effluents. Granular activated carbon is structurally strong, highly resistance to attrition and wearing, large and can easily separate from the effluents. However, its surface is highly hydrophobic and has little surface charge thereby reducing its adsorption capacity for anion or cation. This article reviews surfactant modification of activated carbon to enhance its adsorption capacity for inorganic contaminants and key factors affecting the adsorption efficiency. They include initial concentration of contaminants, contact time, solution pH, solution temperature, adsorbent concentration, ionic strength, competing ions, type of surfactant, and surfactant concentration. The modified activated carbon usually shows maximum contaminant uptake around its critical micelles concentration. Surfactant modification reduces specific surface area and/or micro pore volume but hot NaOH or HNO3 treatment before surfactant modification minimises this drawbacks and increases the net surface charge. Overall, surfactant modification is a simple but efficient method of enhancing adsorption capacity of activated carbon for removing anion or cation from aqueous solution. However, a handful publication is available on the regeneration of the spent (saturated) surfactant modified activated carbons. Hence, more research efforts should be directed towards proper regenerating reagents and the optimise conditions such as contact time, concentration, and temperature for regenerating spent modified activated carbons.
文摘Common ways of disposing waste plastic such as incineration and landfilling have negative impacts on the environment. Partial replacement of natural aggregate in concrete with waste plastic including polyethylene terephthalate (PET) is more environmental friendly and sustainable. The effect of adding 5% to 20% waste plastic by volume of natural coarse aggregate (“gravel”) and plastic particle size (3 to 7 mm) on the density and compressive strength of plastic-concrete mix after 28 days of curing was studied. The results showed that density of the concrete decreased from 2406.7 to 2286.7 kg/m3 as waste plastic increased from 5% to 20% v/v compared with 2443.3 kg/m3 recorded by concrete without waste plastic. Change in particle size from 3 to 7 mm has no significant effect on the density of the plastic-concrete mix. The compressive strength decreased as the volume and particle size of waste plastic increased. When waste plastic volume changed from 5% to 20% v/v, the compressive strength decreased from 20.5 to 15 MPa, 18.6 to 14.3 MPa and 17.2 to 13.8 MPa for 3, 5 and 7 mm waste plastic particle size respectively while the concrete without plastic has 21.33 MPa. Therefore, the addition of 5% (v/v gravel) of flaky waste plastic in the concrete produces a lightweight concrete which could offer economic benefit without substantially reducing the compressive strength of the plastic-concrete mix.
文摘Microalgal phospholipid bilayer contributes to the molar excesses of methanol and high acid concentration required in reactive extraction to achieve high fatty acid methyl ester (FAME) yield. This study reports an investigation into the effects of pre-soaking Nannochloropsis occulata in methanol at 600:1 and 1000:1 methanol to oil molar ratios prior to acid-catalyzed in situ transesterification at 8.5:1 and 15:1 H2SO4 to oil molar ratios on the FAME yield. The results showed that the pre-soaked Nannochloropsis occulata produced a higher FAME yield at the two tested methanol to oil molar ratios and acid concentrations than the un-soaked, resulting in a reduction in methanol volume and acid concentration. A maximum FAME yield of 98.4% ± 1.3% was obtained for the pre-soaked Nannochloropsis occulata at 1000:1 methanol to oil molar ratio and 15:1 H2SO4 to oil molar ratio. Both the phosphorus mass balance and conversion of the isolated phospholipids into FAME revealed that pre-soaking solubilizes the phospholipid bilayer to some degree, and contributes to an increased FAME yield.
