Cadmium sorption behavior of granular activated carbon oxidized with nitric acid was systematically studied by sets of the equilibrium and time-based experiments under various conditions. The cadmium adsorption capaci...Cadmium sorption behavior of granular activated carbon oxidized with nitric acid was systematically studied by sets of the equilibrium and time-based experiments under various conditions. The cadmium adsorption capacity of oxidized granular activated carbon enlarged with an increase in pH, and reduced with an increase in ionic strength. Experimental data were evaluated to find out kinetic characteristics. Adsorption processes were found to follow pseudo-second order rate equation. Adsorption isotherms correlate well with the Langmuir isotherm model and the maximum sorption capacity of cadmium evaluated is 51.02 μmol/g. Thermodynamic parameters were calculated based on Van＇t Hoff equation. Equilibrium constant Kd was evaluated from Freundlich isotherm model constants, Langmuir isotherm model constants, and isotherms, respectively. The average change of standard adsorption heat ΔH^0 was -25.29 kJ/mol. Negative ΔH^0 and ΔG^0 values indicate the adsorption process for cadmium onto the studied activated carbon is exothermic and spontaneous. The standard entropy ΔS^0 was also negative, which suggests a decrease in the freedom of the system.展开更多
The objective of this study was to investigate the feasibility of using a granular activated carbon-biofilm configured packed column system in the deeolodzation of azo dye Acid Orange 7-containing wastewater.The Acid ...The objective of this study was to investigate the feasibility of using a granular activated carbon-biofilm configured packed column system in the deeolodzation of azo dye Acid Orange 7-containing wastewater.The Acid Orange 7-degrading microbial from anaerobic sequencing batch reactor which treating the azo dye-containing wastewater for more than 200 d was immobilized on spent granular activated carbon(GAC)through attachment.The GAC-biofilm configured packed column system showed the ability to decolorize 10...展开更多
Granular activated carbon (GAC) anaerobic fluidized bed reactor was applied to treating phenols wastewater. When influent phenol concentration was 1000 mg/L, volume loadings of phenol and COD Cr were 0 39 kg/(m...Granular activated carbon (GAC) anaerobic fluidized bed reactor was applied to treating phenols wastewater. When influent phenol concentration was 1000 mg/L, volume loadings of phenol and COD Cr were 0 39 kg/(m 3·d) and 0 98 kg/(m 3·d), their removal rates were 99 9% and 96 4% respectively. From analyzing above results, the main mechanisms of the process are that through fluidizing GAC, its adsorption is combined with biodegradation, both activities are brought into full play, and phenol in wastewater is effectively decomposed. Meanwhile problems concerning gas liquid separation and medium plugging are well solved.展开更多
The pentachlorophenol （PCP） adsorbed granular activated carbon （GAC） was treated by dielectric barrier discharge （DBD） plasma. The effects of DBD plasma on the structure of GAC and PCP decomposition were analyze...The pentachlorophenol （PCP） adsorbed granular activated carbon （GAC） was treated by dielectric barrier discharge （DBD） plasma. The effects of DBD plasma on the structure of GAC and PCP decomposition were analyzed by N2 adsorption, thermogravimetric, scanning electron microscopy （SEM）, X-ray photoelectron spectroscopy （XPS） and gas chromatographymass spectrometry （GC-MS）. The experimental data of adsorption kinetics and thermodynamics of PCP on GAC were fitted with different kinetics and isotherm models, respectively. The results indicate that the types of N2 adsorption isotherm of GAC are not changed by DBD plasma, while the specific surface area and pore volume increase after DBD plasma treatment. It is found that the weight loss of the saturated GAC is the highest, on the contrary, the weight loss of DBD treated GAC is the least because of reduced PCP residue on the GAC. The XPS spectra and SEM image suggest that some PCP on the GAC is removed by DBD plasma, and the surface of GAC treated by DBD plasma presents irregular and heterogeneous morphology. The GC-MS identification of by-products shows that two main dechlorination intermediate products, tetrachlorophenol and trichlorophenol, are distinguished. The fitting results of experimental data of adsorption kinetics and thermodynamics indicate that the pseudo-first-order and pseudo-second order models can be used for the prediction of the kinetics of virgin GAC and DBD treated GAC for PCP adsorption, and the Langmuir isotherm model fits better with the data of adsorption isotherm than the Freundlich isotherm in the adsorption of PCP on virgin GAC and DBD treated GAC.展开更多
The use of powdered activated carbon for fouling control in the membrane processes is limited by some secondary problems associated with its use, like cake formation, long backwash times and blackening of pipes. Granu...The use of powdered activated carbon for fouling control in the membrane processes is limited by some secondary problems associated with its use, like cake formation, long backwash times and blackening of pipes. Granular activated carbon (GAC) was used as an alternative of powdered activated carbon due to its large particle size which was kept from being entering into the membrane system. The secondary problems associated with the use of powdered activated carbon as foul control were not observed for granular activated carbon. Langmuir and Freundlich adsorption were used to describe the adsorption of 2,4-D and paraquat on GAC. Adsorption capacity of adsorbent was high for 2,4-D as compared to paraquat. Also, the R2 value was high for Langmuir model as compared to Freundlich model. Retention percentage of 2,4-D by membrane was high and thus the decline in permeate flux was high as compared to paraquat in ultrafiltration (UF) membrane process. 100% retention of 2,4-D was achieved in GAC/UF hybrid system. Improved permeate fluxes were observed for both contaminants in the hybrid system.展开更多
In order to improve adsorption capacity of granular activated carbon (GAC), potassium permanganate was used to react with GAC to change the surface properties and improve the adsorption capacity of GAC. By batch exper...In order to improve adsorption capacity of granular activated carbon (GAC), potassium permanganate was used to react with GAC to change the surface properties and improve the adsorption capacity of GAC. By batch experiments, improvement of adsorption capacity of potassium permanganate modified GAC (GACM) was studied. The influence of adsorption time, temperature, ratio of phenol with GAC/GACM, initial concentration of phenol and pH on adsorption efficiency of GACM was studied. The results showed that modified by potassium permanganate, the adsorption capacity of GAC improved to a higher level. The removal efficiency of phenol increased to about 20%.展开更多
Comparative experiments on the inactivation of Copepod were investigated in southern China. The 100% of inactivation effect may be attained by 3.0 mg/L of ozone for contacting time of 25 min, whereas 0.5 mg/L of dosag...Comparative experiments on the inactivation of Copepod were investigated in southern China. The 100% of inactivation effect may be attained by 3.0 mg/L of ozone for contacting time of 25 min, whereas 0.5 mg/L of dosage resulted in only 30% of inactivation rate. Copepod may not be completely inactivated by ozone oxidation for feasible dosage limited by higher bromide in raw water. The favorable environment of granular activated carbon （GAC） filter provided Copepod with conditions for excess propagation, The disinfection experimental results show that the inactivation rate is 90% by 2.0 mg/L of chloramines for contacting time of 30 min, whereas only 70% is attained with chlorine. The GC-MS examination indicates that the total organic substance is increased to 92 specie： inciuding 13 sorts of halogenated hydrocarbon by chlorine disnfection, which is more than that of chloramines. More products of bromiinated trihalomethanes occur in treated water by chlorine, disinfection and total amount of THMs is 3 times as high as that of chloramines.展开更多
The aim of the present work is to remove heavy metals （copper, manganese, and zinc） from industrial wastewater of Baiji refinery using GAC （granular activated carbon）. The most important factors affecting adsorpti...The aim of the present work is to remove heavy metals （copper, manganese, and zinc） from industrial wastewater of Baiji refinery using GAC （granular activated carbon）. The most important factors affecting adsorption process have been studied, which are granular activated carbon thickness, H, inlet pollutant concentration, Cv, and liquid hourly space velocity, LHSV. All experiments were performed under constant temperature at 25℃ and pH = 7. The experimental apparatus was designed and constructed to enable controlling of the operating conditions. Employing five levels for each of H and LHSV and three levels for Co required 75 runs for each metal. Box-Wilson method was used to reduce the number of experiments to 15 for each metal. The results indicated that copper, manganese, and zinc can be completely removed from wastewater using activated carbon. However, breakthrough time for zinc is low. It is also shown that breakthrough time （TB） and exhaustion time （TE） are inversely proportional with pollutant concentration and LHSV （liquid hour space velocity） while it is directly proportional with the thickness of activated carbon column.展开更多
This work investigated the effect of granular activated carbon adsorption （GACA） on fluorescence characteristics of dissolved organic matter （DOM） in secondary effluent, by means of excitation-emission matrix （EE...This work investigated the effect of granular activated carbon adsorption （GACA） on fluorescence characteristics of dissolved organic matter （DOM） in secondary effluent, by means of excitation-emission matrix （EEM） spectra, the fluorescence regional integra- tion （FRI） method, synchronous spectra, the fluorescence index defined as the ratio of fluorescence emission intensity at wavelength 450nm to that at 500nm at excitation （λex）= 370 am, and the wavelength that corre- sponds to the position of the normalized emission band at its half intensity （λ0.5）. DOM in the secondary effluent from the North Wastewater Treatment Plant （Shenyang, China） was fractionated using XAD resins into 5 fractions： hydrophobic acid （HPO-A）, hydrophobic neutral （HPO- N）, transphilic acid （TPI-A）, transphi｜ic neutral （TPI-N） and hydrophilic fraction （HPI）. Results showed that fluorescent materials in HPO-N and TPI-N were less readily removed than those in the other fractions by GACA. The relative content of fluorescent materials in HPO-A, TPI-A and HPI decreased whereas that in HPO- N and TPI-N increased as a consequence of GACA. Polycyclic aromatics in all DOM fractions were preferen- tially absorbed by GACA, in comparison with bulk DOM expressed as DOC. On the other hand, the adsorption of aromatic amino acids and humic acid-like fluorophores exhibiting fluorescence peaks in synchronous spectra by GACA seemed to be dependent on the acid/neutralproperties of DOM fractions. All five fractions had decreased fluorescence indices as a result of GACA. GACA led to a decreased λ0.5 value for HPO-A, increased ,λ0.5 values for HPO-N, TPI-A and HPI, and a consistent λ0.5 value for TPI-N.展开更多
TiO2 nanoparticle-coated granular activated carbon (GAC) composite photocatalysts (CPs) were suc-cessfully prepared by a molecular adsorption-deposition (MAD) method. The CPs were detected by scanning electron microsc...TiO2 nanoparticle-coated granular activated carbon (GAC) composite photocatalysts (CPs) were suc-cessfully prepared by a molecular adsorption-deposition (MAD) method. The CPs were detected by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), BET surface area and UV-Vis adsorption spectroscopy, and their photoactivity was evaluated by methyl orange (MO) photodegradation. The results show that small-sized TiO2 nanoparticles were dispersed well, deposited on the surface of GAC, and showed slight blue shift in comparison with pure TiO2. With the increase in TiO2 content, the CPs showed band gaps in lower energy, smaller surface areas and the higher content of Ti3+ ions. Compared with pure TiO2 and others CPs samples, CPs-382 sample showed the highest photoactivity due to the optimum TiO2 content and surface area besides the synergic effect of photocatalytic degradation of TiO2 and adsorptive property of GAC. In addition, the CPs could be very easily reclaimed, recycled and reused for methyl orange removal while high photoactivity is pre-served.展开更多
In this study,a highly porous chemically activated granular activated carbon(GAC)was prepared from coconut husk and tested as an adsorbent to remove nitrate from contaminated groundwater.The prepared GAC was character...In this study,a highly porous chemically activated granular activated carbon(GAC)was prepared from coconut husk and tested as an adsorbent to remove nitrate from contaminated groundwater.The prepared GAC was characterized by Fouriertransform infrared spectroscopy(FTIR),thermogravimetric and differential thermal analysis(TGA/DTA),scanning electron microscopy(SEM)and the Brunauer-Emmett-Teller(BET)surface area(SBET)analysis.The effects of various process parameters such as initial nitrate concentration,contact time and adsorbent dose on nitrate removal efficiency(response)by the modified GAC were investigated using the statistically significant response surface methodology and Box-Behnken design of experiments.The experimental data were fitted to well-known adsorption isotherms and kinetic models to ascertain the mechanism of the adsorption process.Analysis of variance(ANOVA)was performed to determine the significance of the individual and the interactive effects of process variables on the response.The BET surface area(SBET)and micropore volume of the prepared GAC from coconut husk was 1120 m^(2)/g and 0.392 cm^(3)/g,respectively.The experimental results showed that physisorption was the main adsorption mechanism governing the process,while the rate of adsorption was limited at initial nitrate concentrations>10 mg/L.The Langmuir mono-layer adsorption isotherm best fitted the experimental data with a maximum adsorption capacity of 6.0±1.3 mg/g(~92.5%)with an adsorbent dose of 0.1 g/50 mL,an equilibrium time of 6 h at 28±2℃,and at pH 7.6(±0.2).Among the tested process variables,the adsorbent dose and initial nitrate concentration showed significant effects on the nitrate removal efficiency.展开更多
Chloroacetamide herbicides,namely acetochlor and metolachlor,are common herbicides used on corn and soybean fields.Dichloroacetamide safeners,namely benoxacor and furilazole,are commonly used in formulations containin...Chloroacetamide herbicides,namely acetochlor and metolachlor,are common herbicides used on corn and soybean fields.Dichloroacetamide safeners,namely benoxacor and furilazole,are commonly used in formulations containing chloroacetamide herbicides.Extensive reports on adsorption of chloroacetamide herbicides are available,yet little information exists regarding adsorption potential of co-applied safeners.Herein,the adsorption and desorption characteristics of selected herbicide safeners to granular activated carbon(GAC) and in agricultural soils are reported.Further,soil column studies were performed to understand the leaching behaviour of the herbicide Dual II Magnum.Equilibrium sorption experiments of safeners to three agricultural soils and one GAC showed that adsorption was best fitted by the Freundlich isotherm.The Freundlich adsorption constant,Kf,for benoxacor and furilazole sorption onto three agricultural soils ranged from0.1 to 0.27 and 0.1 to 0.13(mg/g) x(mg/L)(1/n),respectively.The Kf for benoxacor and furilazole to GAC was 6.4 and 3.4(mg/g) x(mg/L)(1/n),respectively,suggesting more favorable sorption of benoxacor to GAC than furilazole to GAC.The sorption to soils was reversible as almost 40%-90% of both safeners was desorbed from three soils.These results were validated in four replicated soil column studies,where S-metolachlor was shown to leach similarly to the safener benoxacor,originating from the herbicide formulation.The leaching of S-metolachlor and benoxacor was influenced by soil texture.Cumulatively,these results show that safeners will move through the environment to surface waters similarly to the active ingredients in herbicides,but may be removed during drinking water treatment via GAC.展开更多
基金Project supported by the Hi-Tech Research and Development Program(863)of China(No.2002AA601130)the Basic Science Research Program of Shanghai(No.05JC 14059).
文摘Cadmium sorption behavior of granular activated carbon oxidized with nitric acid was systematically studied by sets of the equilibrium and time-based experiments under various conditions. The cadmium adsorption capacity of oxidized granular activated carbon enlarged with an increase in pH, and reduced with an increase in ionic strength. Experimental data were evaluated to find out kinetic characteristics. Adsorption processes were found to follow pseudo-second order rate equation. Adsorption isotherms correlate well with the Langmuir isotherm model and the maximum sorption capacity of cadmium evaluated is 51.02 μmol/g. Thermodynamic parameters were calculated based on Van＇t Hoff equation. Equilibrium constant Kd was evaluated from Freundlich isotherm model constants, Langmuir isotherm model constants, and isotherms, respectively. The average change of standard adsorption heat ΔH^0 was -25.29 kJ/mol. Negative ΔH^0 and ΔG^0 values indicate the adsorption process for cadmium onto the studied activated carbon is exothermic and spontaneous. The standard entropy ΔS^0 was also negative, which suggests a decrease in the freedom of the system.
文摘The objective of this study was to investigate the feasibility of using a granular activated carbon-biofilm configured packed column system in the deeolodzation of azo dye Acid Orange 7-containing wastewater.The Acid Orange 7-degrading microbial from anaerobic sequencing batch reactor which treating the azo dye-containing wastewater for more than 200 d was immobilized on spent granular activated carbon(GAC)through attachment.The GAC-biofilm configured packed column system showed the ability to decolorize 10...
文摘Granular activated carbon (GAC) anaerobic fluidized bed reactor was applied to treating phenols wastewater. When influent phenol concentration was 1000 mg/L, volume loadings of phenol and COD Cr were 0 39 kg/(m 3·d) and 0 98 kg/(m 3·d), their removal rates were 99 9% and 96 4% respectively. From analyzing above results, the main mechanisms of the process are that through fluidizing GAC, its adsorption is combined with biodegradation, both activities are brought into full play, and phenol in wastewater is effectively decomposed. Meanwhile problems concerning gas liquid separation and medium plugging are well solved.
基金supported by National Natural Science Foundation of China （No. 21107085） and National High Technology Research and Development Program of China （No. 2008AA06Z308）
文摘The pentachlorophenol （PCP） adsorbed granular activated carbon （GAC） was treated by dielectric barrier discharge （DBD） plasma. The effects of DBD plasma on the structure of GAC and PCP decomposition were analyzed by N2 adsorption, thermogravimetric, scanning electron microscopy （SEM）, X-ray photoelectron spectroscopy （XPS） and gas chromatographymass spectrometry （GC-MS）. The experimental data of adsorption kinetics and thermodynamics of PCP on GAC were fitted with different kinetics and isotherm models, respectively. The results indicate that the types of N2 adsorption isotherm of GAC are not changed by DBD plasma, while the specific surface area and pore volume increase after DBD plasma treatment. It is found that the weight loss of the saturated GAC is the highest, on the contrary, the weight loss of DBD treated GAC is the least because of reduced PCP residue on the GAC. The XPS spectra and SEM image suggest that some PCP on the GAC is removed by DBD plasma, and the surface of GAC treated by DBD plasma presents irregular and heterogeneous morphology. The GC-MS identification of by-products shows that two main dechlorination intermediate products, tetrachlorophenol and trichlorophenol, are distinguished. The fitting results of experimental data of adsorption kinetics and thermodynamics indicate that the pseudo-first-order and pseudo-second order models can be used for the prediction of the kinetics of virgin GAC and DBD treated GAC for PCP adsorption, and the Langmuir isotherm model fits better with the data of adsorption isotherm than the Freundlich isotherm in the adsorption of PCP on virgin GAC and DBD treated GAC.
文摘The use of powdered activated carbon for fouling control in the membrane processes is limited by some secondary problems associated with its use, like cake formation, long backwash times and blackening of pipes. Granular activated carbon (GAC) was used as an alternative of powdered activated carbon due to its large particle size which was kept from being entering into the membrane system. The secondary problems associated with the use of powdered activated carbon as foul control were not observed for granular activated carbon. Langmuir and Freundlich adsorption were used to describe the adsorption of 2,4-D and paraquat on GAC. Adsorption capacity of adsorbent was high for 2,4-D as compared to paraquat. Also, the R2 value was high for Langmuir model as compared to Freundlich model. Retention percentage of 2,4-D by membrane was high and thus the decline in permeate flux was high as compared to paraquat in ultrafiltration (UF) membrane process. 100% retention of 2,4-D was achieved in GAC/UF hybrid system. Improved permeate fluxes were observed for both contaminants in the hybrid system.
文摘In order to improve adsorption capacity of granular activated carbon (GAC), potassium permanganate was used to react with GAC to change the surface properties and improve the adsorption capacity of GAC. By batch experiments, improvement of adsorption capacity of potassium permanganate modified GAC (GACM) was studied. The influence of adsorption time, temperature, ratio of phenol with GAC/GACM, initial concentration of phenol and pH on adsorption efficiency of GACM was studied. The results showed that modified by potassium permanganate, the adsorption capacity of GAC improved to a higher level. The removal efficiency of phenol increased to about 20%.
基金National Natural Science Foundation of China(No.50808065)National Key High-Tech Program(863) of China(No.2006AA06Z311)Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes Open Project,China(No.2006KJ006)
文摘Comparative experiments on the inactivation of Copepod were investigated in southern China. The 100% of inactivation effect may be attained by 3.0 mg/L of ozone for contacting time of 25 min, whereas 0.5 mg/L of dosage resulted in only 30% of inactivation rate. Copepod may not be completely inactivated by ozone oxidation for feasible dosage limited by higher bromide in raw water. The favorable environment of granular activated carbon （GAC） filter provided Copepod with conditions for excess propagation, The disinfection experimental results show that the inactivation rate is 90% by 2.0 mg/L of chloramines for contacting time of 30 min, whereas only 70% is attained with chlorine. The GC-MS examination indicates that the total organic substance is increased to 92 specie： inciuding 13 sorts of halogenated hydrocarbon by chlorine disnfection, which is more than that of chloramines. More products of bromiinated trihalomethanes occur in treated water by chlorine, disinfection and total amount of THMs is 3 times as high as that of chloramines.
文摘The aim of the present work is to remove heavy metals （copper, manganese, and zinc） from industrial wastewater of Baiji refinery using GAC （granular activated carbon）. The most important factors affecting adsorption process have been studied, which are granular activated carbon thickness, H, inlet pollutant concentration, Cv, and liquid hourly space velocity, LHSV. All experiments were performed under constant temperature at 25℃ and pH = 7. The experimental apparatus was designed and constructed to enable controlling of the operating conditions. Employing five levels for each of H and LHSV and three levels for Co required 75 runs for each metal. Box-Wilson method was used to reduce the number of experiments to 15 for each metal. The results indicated that copper, manganese, and zinc can be completely removed from wastewater using activated carbon. However, breakthrough time for zinc is low. It is also shown that breakthrough time （TB） and exhaustion time （TE） are inversely proportional with pollutant concentration and LHSV （liquid hour space velocity） while it is directly proportional with the thickness of activated carbon column.
文摘This work investigated the effect of granular activated carbon adsorption （GACA） on fluorescence characteristics of dissolved organic matter （DOM） in secondary effluent, by means of excitation-emission matrix （EEM） spectra, the fluorescence regional integra- tion （FRI） method, synchronous spectra, the fluorescence index defined as the ratio of fluorescence emission intensity at wavelength 450nm to that at 500nm at excitation （λex）= 370 am, and the wavelength that corre- sponds to the position of the normalized emission band at its half intensity （λ0.5）. DOM in the secondary effluent from the North Wastewater Treatment Plant （Shenyang, China） was fractionated using XAD resins into 5 fractions： hydrophobic acid （HPO-A）, hydrophobic neutral （HPO- N）, transphilic acid （TPI-A）, transphi｜ic neutral （TPI-N） and hydrophilic fraction （HPI）. Results showed that fluorescent materials in HPO-N and TPI-N were less readily removed than those in the other fractions by GACA. The relative content of fluorescent materials in HPO-A, TPI-A and HPI decreased whereas that in HPO- N and TPI-N increased as a consequence of GACA. Polycyclic aromatics in all DOM fractions were preferen- tially absorbed by GACA, in comparison with bulk DOM expressed as DOC. On the other hand, the adsorption of aromatic amino acids and humic acid-like fluorophores exhibiting fluorescence peaks in synchronous spectra by GACA seemed to be dependent on the acid/neutralproperties of DOM fractions. All five fractions had decreased fluorescence indices as a result of GACA. GACA led to a decreased λ0.5 value for HPO-A, increased ,λ0.5 values for HPO-N, TPI-A and HPI, and a consistent λ0.5 value for TPI-N.
基金the Natural Science Foundation of Hunan Province (Grant No.06JJ50150)the Scientific Research Fund of Science and Technology Department of Hunan Province (Grant No.2007GK3060)Jishou University (Grant No.JSDXKYZZ200648)
文摘TiO2 nanoparticle-coated granular activated carbon (GAC) composite photocatalysts (CPs) were suc-cessfully prepared by a molecular adsorption-deposition (MAD) method. The CPs were detected by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), BET surface area and UV-Vis adsorption spectroscopy, and their photoactivity was evaluated by methyl orange (MO) photodegradation. The results show that small-sized TiO2 nanoparticles were dispersed well, deposited on the surface of GAC, and showed slight blue shift in comparison with pure TiO2. With the increase in TiO2 content, the CPs showed band gaps in lower energy, smaller surface areas and the higher content of Ti3+ ions. Compared with pure TiO2 and others CPs samples, CPs-382 sample showed the highest photoactivity due to the optimum TiO2 content and surface area besides the synergic effect of photocatalytic degradation of TiO2 and adsorptive property of GAC. In addition, the CPs could be very easily reclaimed, recycled and reused for methyl orange removal while high photoactivity is pre-served.
文摘In this study,a highly porous chemically activated granular activated carbon(GAC)was prepared from coconut husk and tested as an adsorbent to remove nitrate from contaminated groundwater.The prepared GAC was characterized by Fouriertransform infrared spectroscopy(FTIR),thermogravimetric and differential thermal analysis(TGA/DTA),scanning electron microscopy(SEM)and the Brunauer-Emmett-Teller(BET)surface area(SBET)analysis.The effects of various process parameters such as initial nitrate concentration,contact time and adsorbent dose on nitrate removal efficiency(response)by the modified GAC were investigated using the statistically significant response surface methodology and Box-Behnken design of experiments.The experimental data were fitted to well-known adsorption isotherms and kinetic models to ascertain the mechanism of the adsorption process.Analysis of variance(ANOVA)was performed to determine the significance of the individual and the interactive effects of process variables on the response.The BET surface area(SBET)and micropore volume of the prepared GAC from coconut husk was 1120 m^(2)/g and 0.392 cm^(3)/g,respectively.The experimental results showed that physisorption was the main adsorption mechanism governing the process,while the rate of adsorption was limited at initial nitrate concentrations>10 mg/L.The Langmuir mono-layer adsorption isotherm best fitted the experimental data with a maximum adsorption capacity of 6.0±1.3 mg/g(~92.5%)with an adsorbent dose of 0.1 g/50 mL,an equilibrium time of 6 h at 28±2℃,and at pH 7.6(±0.2).Among the tested process variables,the adsorbent dose and initial nitrate concentration showed significant effects on the nitrate removal efficiency.
文摘Chloroacetamide herbicides,namely acetochlor and metolachlor,are common herbicides used on corn and soybean fields.Dichloroacetamide safeners,namely benoxacor and furilazole,are commonly used in formulations containing chloroacetamide herbicides.Extensive reports on adsorption of chloroacetamide herbicides are available,yet little information exists regarding adsorption potential of co-applied safeners.Herein,the adsorption and desorption characteristics of selected herbicide safeners to granular activated carbon(GAC) and in agricultural soils are reported.Further,soil column studies were performed to understand the leaching behaviour of the herbicide Dual II Magnum.Equilibrium sorption experiments of safeners to three agricultural soils and one GAC showed that adsorption was best fitted by the Freundlich isotherm.The Freundlich adsorption constant,Kf,for benoxacor and furilazole sorption onto three agricultural soils ranged from0.1 to 0.27 and 0.1 to 0.13(mg/g) x(mg/L)(1/n),respectively.The Kf for benoxacor and furilazole to GAC was 6.4 and 3.4(mg/g) x(mg/L)(1/n),respectively,suggesting more favorable sorption of benoxacor to GAC than furilazole to GAC.The sorption to soils was reversible as almost 40%-90% of both safeners was desorbed from three soils.These results were validated in four replicated soil column studies,where S-metolachlor was shown to leach similarly to the safener benoxacor,originating from the herbicide formulation.The leaching of S-metolachlor and benoxacor was influenced by soil texture.Cumulatively,these results show that safeners will move through the environment to surface waters similarly to the active ingredients in herbicides,but may be removed during drinking water treatment via GAC.
