The reaction studied in this work is the synthesis of nanometric size calcium carbonate particles by carbonation of a suspension of lime, which represents the most common industrial route. It consists in bubbling carb...The reaction studied in this work is the synthesis of nanometric size calcium carbonate particles by carbonation of a suspension of lime, which represents the most common industrial route. It consists in bubbling carbon dioxide in a suspension of lime to obtain precipitated calcium carbonate (PCC). PCC is a mineral filler with various applications: sealants, paints, paper, ink, pharmacy, cosmetics, food etc. However, there is a challenge related to the synthesis and the use of this precipitate: the agglomeration of the monoparticles. The aim of this work is then to understand the mechanisms of this phenomenon and to study its kinetics to improve the run of the process and the control of its impact on the final product. Experiments realized with a high concentration in sodium chloride (2 M) showed that the modification of the electrostatic environment did not change the particle size distribution and the morphology of the agglomerates. This indicates that the electrostatic interactions are not responsible for the agglomeration but the formation of crystalline bridges induced by the crystal growth. Thus, thanks to an agglomeration model including the crystal growth rate, the agglomeration kernel β and the agglomeration constant β0 can be determined using a mathematical treatment of the experimental particle size distributions. Finally, by varying the experimental conditions, it appears that the agglomeration constant increases with the temperature whereas there is an optimal value regarding the shear rate.展开更多
The objective of this work is to investigate the influence of contact pressure and sliding speed on the coefficient of friction and wear of an activated carbon-epoxy composite derived from palm kernel under dry slidin...The objective of this work is to investigate the influence of contact pressure and sliding speed on the coefficient of friction and wear of an activated carbon-epoxy composite derived from palm kernel under dry sliding conditions.A wear mode map approach was employed to identify the transitions from mild to severe wear of the composite.The dry sliding test was executed by utilizing a ball-on-disc tribometer at different contact pressures and sliding speeds with a constant sliding distance and operating temperature.The results showed that,regardless of the sliding speed,the friction coefficient and wear rate of the composite increased drastically when a critical limit of contact pressure is exceeded.As for the sliding speed,both the friction coefficient and wear rate increased first and thereafter decreased at a higher speed of 500 rpm.A wear mode map is proposed to classify the boundary from mild to severe wear regimes.The predominant wear failures identified include micro-crack,fine grooves,debonding,delamination,debris,broken carbon,and fracture.展开更多
The present study systematically investigated the influence of synthesis conditions(duration,reaction medium,and doping concentration)and formation mechanism of carbon dots(CDs)derived from low-cost and abundant bioma...The present study systematically investigated the influence of synthesis conditions(duration,reaction medium,and doping concentration)and formation mechanism of carbon dots(CDs)derived from low-cost and abundant biomass palm kernel shell(PKS).Surprisingly,the dopant(urea)did not enhance the photoluminescence of CDs as expected,which could be attributed to the low reactivity between the dopant and PKS macromolecules.Variation of synthesis duration from 30 to 120 s clearly indicated the formation mechanism of CDs,involving the stages of dehydration,carbonization,and nucleation.The CDs with the highest photoluminescent intensity and quantum yield was obtained at synthesis duration of 90 s,aligned well with the perfect spherical shape of CDs and the synergistic effects of both surface and carbogenic core conditions.Understanding the formation mechanism could be used to optimize the synthesis of CDs,and hence linked to quantum yield and fluorescent intensity.In terms of application potential,the CDs illuminated well as fluorescent ink and in bacteria cells imaging.The potential of CDs as sensing material has also been proven with the quenching of fluorescence in the presence of metal ions.The linear range for detection of Cu2+ions was 0.1–0.5 mM with a detection limit as low as 0.05 mM.This signifies the potential of CDs fabricated from PKS as a low-cost and easily available material for Cu2+ions detection in aqueous solution.The CDs possessed reasonable photo stability as indicated by its consistent fluorescence level even after exposure to UV radiation for a prolonged period of 180 minutes.Overall,a simple,straightforward,and fast method is developed to synthesis strong blue emissive CDs from green PKS that are potentially suitable for Cu2+ions sensing in real application.展开更多
First, the date palm kernel is used to produce granular activated carbon （GAC） by a physiochemical activation process. The process involves six steps： washing, drying, crushing, sieving, carbonization, and activati...First, the date palm kernel is used to produce granular activated carbon （GAC） by a physiochemical activation process. The process involves six steps： washing, drying, crushing, sieving, carbonization, and activation. Secondly, the ability of the produced GAC to remove pollutants is examined through batch experiments of residual chlorine adsorption whereas the equilibrium isotherm experimental data are tested for the Langmuir and Freundlich isotherms equations. Thirdly, the experimental and theoretical study of dynamic adsorption process and the effect of major operating parameters on dynamic adsorption are investigated. The results show that the Langmuir isotherm gives the best fitting to experimental data, which indicates that the residual chlorine adsorption can be characterized by mono layer adsorption behavior. The produced GAC has a great potential as an adsorbent for residual chlorine in water systems and it can compete favorably with the conventional adsorbents. The Thomas extended model with combined mass transfer resistances is used for verifying the experimental results and the results show that the proposed model coincides well with the experimental data of the dynamic adsorption process.展开更多
文摘The reaction studied in this work is the synthesis of nanometric size calcium carbonate particles by carbonation of a suspension of lime, which represents the most common industrial route. It consists in bubbling carbon dioxide in a suspension of lime to obtain precipitated calcium carbonate (PCC). PCC is a mineral filler with various applications: sealants, paints, paper, ink, pharmacy, cosmetics, food etc. However, there is a challenge related to the synthesis and the use of this precipitate: the agglomeration of the monoparticles. The aim of this work is then to understand the mechanisms of this phenomenon and to study its kinetics to improve the run of the process and the control of its impact on the final product. Experiments realized with a high concentration in sodium chloride (2 M) showed that the modification of the electrostatic environment did not change the particle size distribution and the morphology of the agglomerates. This indicates that the electrostatic interactions are not responsible for the agglomeration but the formation of crystalline bridges induced by the crystal growth. Thus, thanks to an agglomeration model including the crystal growth rate, the agglomeration kernel β and the agglomeration constant β0 can be determined using a mathematical treatment of the experimental particle size distributions. Finally, by varying the experimental conditions, it appears that the agglomeration constant increases with the temperature whereas there is an optimal value regarding the shear rate.
基金supported by the grant from the Ministry of Higher Education Malaysia(Grant number:FRGS/1/2016/TK10/FKM-CARE/F00315)
文摘The objective of this work is to investigate the influence of contact pressure and sliding speed on the coefficient of friction and wear of an activated carbon-epoxy composite derived from palm kernel under dry sliding conditions.A wear mode map approach was employed to identify the transitions from mild to severe wear of the composite.The dry sliding test was executed by utilizing a ball-on-disc tribometer at different contact pressures and sliding speeds with a constant sliding distance and operating temperature.The results showed that,regardless of the sliding speed,the friction coefficient and wear rate of the composite increased drastically when a critical limit of contact pressure is exceeded.As for the sliding speed,both the friction coefficient and wear rate increased first and thereafter decreased at a higher speed of 500 rpm.A wear mode map is proposed to classify the boundary from mild to severe wear regimes.The predominant wear failures identified include micro-crack,fine grooves,debonding,delamination,debris,broken carbon,and fracture.
文摘The present study systematically investigated the influence of synthesis conditions(duration,reaction medium,and doping concentration)and formation mechanism of carbon dots(CDs)derived from low-cost and abundant biomass palm kernel shell(PKS).Surprisingly,the dopant(urea)did not enhance the photoluminescence of CDs as expected,which could be attributed to the low reactivity between the dopant and PKS macromolecules.Variation of synthesis duration from 30 to 120 s clearly indicated the formation mechanism of CDs,involving the stages of dehydration,carbonization,and nucleation.The CDs with the highest photoluminescent intensity and quantum yield was obtained at synthesis duration of 90 s,aligned well with the perfect spherical shape of CDs and the synergistic effects of both surface and carbogenic core conditions.Understanding the formation mechanism could be used to optimize the synthesis of CDs,and hence linked to quantum yield and fluorescent intensity.In terms of application potential,the CDs illuminated well as fluorescent ink and in bacteria cells imaging.The potential of CDs as sensing material has also been proven with the quenching of fluorescence in the presence of metal ions.The linear range for detection of Cu2+ions was 0.1–0.5 mM with a detection limit as low as 0.05 mM.This signifies the potential of CDs fabricated from PKS as a low-cost and easily available material for Cu2+ions detection in aqueous solution.The CDs possessed reasonable photo stability as indicated by its consistent fluorescence level even after exposure to UV radiation for a prolonged period of 180 minutes.Overall,a simple,straightforward,and fast method is developed to synthesis strong blue emissive CDs from green PKS that are potentially suitable for Cu2+ions sensing in real application.
基金The National Natural Science Foundation of China(No. 51078074)
文摘First, the date palm kernel is used to produce granular activated carbon （GAC） by a physiochemical activation process. The process involves six steps： washing, drying, crushing, sieving, carbonization, and activation. Secondly, the ability of the produced GAC to remove pollutants is examined through batch experiments of residual chlorine adsorption whereas the equilibrium isotherm experimental data are tested for the Langmuir and Freundlich isotherms equations. Thirdly, the experimental and theoretical study of dynamic adsorption process and the effect of major operating parameters on dynamic adsorption are investigated. The results show that the Langmuir isotherm gives the best fitting to experimental data, which indicates that the residual chlorine adsorption can be characterized by mono layer adsorption behavior. The produced GAC has a great potential as an adsorbent for residual chlorine in water systems and it can compete favorably with the conventional adsorbents. The Thomas extended model with combined mass transfer resistances is used for verifying the experimental results and the results show that the proposed model coincides well with the experimental data of the dynamic adsorption process.
