Elimination, Kinetics and Thermodynamics of Fe(II) Ions by Adsorption in Static and Dynamic Conditions on Activated Carbons in Aqueous Media

This work investigated the removal, kinetics and thermodynamics of iron(II) ions (Fe(II)) by adsorption in static and dynamic conditions in aqueous media on activated carbons (AC-i30min, AC-i1h, and AC-i24h), prepared from palm nut shells collected in the city of Franceville to Gabon, using potassium hydroxide (KOH) as the activating agent. Results on the elimination of Fe(II) in static and dynamic adsorption on prepared activated carbons (ACs) showed that the AC-i24h adsorbent has the best Fe(II) adsorption capacities at saturation (Qsat). The Qsat obtained on AC-i24h in static and dynamic conditions (17.87 and 10.38 mg/g, respectively) were higher than those of AC-i30min (13.89 and 5.54 mg/g respectively) and AC-i1h (14.92 and 8.64 mg/g respectively). Moreover, the static adsorption was more effective in the removal of Fe(II) ions in aqueous media in our experimental conditions. The percentage removal (%E) of Fe(II) obtained on prepared activated carbons in static conditions was better than those obtained in dynamic conditions, especially on AC-i24h, where the %E was 89.27% in static and 61.56% in dynamic. In kinetics, results showed that the pseudo-second-order kinetic model best described the adsorption mechanisms of Fe(II) on prepared activated carbons in static adsorption, with mainly of chemisorption on the solid surfaces. However, in dynamic conditions, the pseudo-first-order kinetic model was more suitable. In addition to the weak interactions between Fe(II) and the activated carbon surfaces, strong interactions (chemisorption) were also observed. Also, thermodynamic data obtained on AC-i24h in static adsorption indicated that the adsorption of Fe(II) was spontaneous and increased with temperature (ΔG˚ H˚ = 503.54 KJ/mol).

Thermodynamics and kinetics of cadmium adsorption onto oxidized granular activated carbon

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.

The Adsorption of Phenol by Lignite Activated Carbon

The feasibility and adsorption effect of lignite activated carbon for phenol removal from aqueous solutions were evaluated and investigated. A series of tests were performed to look into the influence of various experimental parameters such as contact time, initial phenol concentration, temperature, and pH value on the adsorption of phenol by lignite activated carbon. The experimental data were fitted well with the pseudo-second-order kinetic model. The adsorption is an endothermic process and conforms to Freundlich thermodynamic model. The results indicate that the lignite activated carbon is suitable to be used as an adsorbent material for adsorption of phenol from aqueous solutions.

Enhanced adsorption of phenol from aqueous solution by carbonized trace ZIF-8-decorated activated carbon pellets

Trace zeolitic imidazolate framework-8(ZIF-8)-decorated activated carbon(AC)pellets were synthesized by a facile wet impregnation technique.After pyrolysis of the above composite material,the obtained carbon had a large surface area and pore volume,with traces of Zn on its surface.Subsequently,the capacity of the ZIF8/AC samples to adsorb and remove phenol from aqueous media was evaluated in both batch and column experimental setups.The equilibrium adsorption capacity reached 155.24 mg·g^(-1),which was 2.3 times greater than that of the pure AC(46.24 mg·g^(-1)).In addition,adsorption kinetics were examined by pseudofirst and pseudosecond order models,and adsorption isotherms were fitted into Langmuir and Freundlich equations.The adsorbent could be easily filtered from the solution and washed with methanol and water,while maintaining an efficiency N90% after 4 cycles.The above results make it a potentially reusable candidate for water purification.

Adsorption of Phenol by Activated Carbon Prepared from Waste Rice Straw by Chemical Activation with (NH_4)_2HPO_4

Activated carbons,RS-1,RS-2,and RS-3,prepared from rice straw with(NH4)2HPO4 activation were used as adsorbents for removing phenols from aqueous solutions.The maximum adsorption capacities of phenol for RS-1,RS-2,and RS-3 were 163.9,172.9,and 200.0 mg/g,respectively.The equilibrium data were analyzed by the Langmuir,Freundlich,and Temkin models.It displayed that Langmuir isotherm fitted to the results best.The dimensionless parameter RL indicated the favorable nature of the adsorption of phenol.Otherwise,the kinetic rates were well explained by pseudo-second-order model.According to the results,activated carbon derived from waste rice straw can be a high-performance adsorbent for wastewater treatment.

Preparation of Waste Coffee-grounds Carbon and Study on Phenol Adsorption Ability

The waste coffee-grounds carbon(WCGC)was prepared with H_(3)PO_(4)treated using waste coffee-grounds as precursor.Its adsorption ability was studied using phenol as test molecule.The influence of H_(3)PO_(4)treated,calcined temperature,the initial phenol concentration,the doge of carbon and original pH values on phenol adsorption ability were investigated.Characterization of WCGC was performed by N_(2)adsorption isotherms,Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),and X-ray diffraction(XRD)techniques.First,the second order and Weber-Morris model reaction rate models were used to estimate the WCGC adsorption ability.The results show that the produced WCGC(700℃,2 h)has been graphitized and the layered structure increased BET surface to 435.98 m^(2)/g and adsorption phenol ability.The initial phenol concentration is 50 mg/L,the amount of WCGC(700℃,2 h)is 0.2 g,and the phenol adsorption rate is 97%after 270 min and no intermediate product formation.The adsorption kinetics of the selected WCGC is best fitted by the Weber-Morris model.

Adsorption of Phenol Aqueous Solutions and Two Nitroderivated on Activated Carbon

The adsorption of phenol, p-nitrophenol and 2,4-dinitrophenol in aqueous phase on activated carbon is performed by evaluating factors such as the pH of the solution, it is found that the value in adsorbate molecule is upper and lower of its respective pKa. Likewise, the heterogeneity of the adsorbent solid is evaluated using commercial activated carbon, which is modified by means of oxidation with HNO3 and reduction with H2 fluxing at high temperature, treatments represent variatians in textural properties of solid which changed equally the superficial chemistry of the same. The major concentration of retained plLenol compound in some samples of carbon is produced in pH values which the solute is basically molecular.

Adsorption of phenol from aqueous solution by a hierarchical micro-nano porous carbon material

A hierarchical micro-nano porous carbon material (MNC) was prepared using expanded graphite (EG), sucrose, and phosphoric acid as raw materials, followed by sucrose-phosphoric acid solution impregnation, solidification, carbonization and activation. Nitrogen adsorption and mercury porosimetry show that mixed nanopores and micropores coexist in MNC with a high specific surface area of 1978 m2·g-1 and a total pore volume of 0.99 cm3·g-1. In addition, the MNC is found to consist of EG and activated carbon with the latter deposited on the interior and the exterior surfaces of the EG pores. The thickness of the activated carbon layer is calculated to be about one hundred nanometers and is further confirmed by scanning electron microscope (SEM) and transmission election microscope (TEM). A maximum static phenol adsorption of 241.2 mg·g-1 was obtained by using MNC, slightly higher than that of 220.4 mg·g-1 by using commercial activated carbon (CAC). The phenol adsorption kinetics were investigated and the data fitted well to a pseudo-second-order model. Also, an intra-particle diffusion mechanism was proposed. Furthermore, it is found that the dynamic adsorption capacity of MNC is nearly three times that of CAC. The results suggest that the MNC is a more efficient adsorbent than CAC for the removal of phenol from aqueous solution.

A comparative study of the pore characteristics and phenol adsorption performance of activated carbons prepared from oil-palm shell wastes by steam and combined steam-chemical activation

Oil-palm shell wastes were successfully converted into useful activated carbons in a systematic and novel approach by optimizing the pyrolysis conditions and subsequent steam activation conditions to maximize the BET surface area.The optimal activation conditions were a steam flow rate of 1.13 kg/h,hold time of 1.5 h and temperature of 950℃,yielding BET areas of 1432.94 and 1382.95 m^(2)/g for nitrogen-pyrolyzed and vacuumpyrolyzed chars,respectively.In steam-chemical activation,one-step activation of oil-palm shell in steam with potassium carbonate(K_(2)CO_(3)),sodium carbonate(Na_(2)CO_(3))or potassium chloride(KCl)was conducted,resulting in BET area output order of shell/K_(2)CO_(3)(710.56 m^(2)/g)>shell/KCl(498.55 m^(2)/g)>shell(366.7 m^(2)/g)>shell/Na_(2)CO_(3)(326.62 m^(2)/g).This study reported the first use of KCl and Na_(2)CO_(3)as chemical reagents in one-step steam-chemical activation of biomass.KCl-activated carbon exhibited retardation of tar formation property,resulting in better pore development than pure steam activated carbon.Phenol adsorption of activated carbon is not only a function of the BET surface area but also the type of pyrolysis used prior to physical activation.Activated carbon(BET area of 1192.29 m^(2)/g)pyrolyzed under vacuum could adsorb 87%more phenol than that pyrolyzed in nitrogen flow which had a higher BET area of 1432.94 m^(2)/g.Phenol adsorption capacities of activated carbons are:shell pyrolyzed under vacuum(275.5 mg/g)>shell pyrolyzed in N_(2)flow(147.1 mg/g)>shell/K_(2)CO_(3)(145.7 mg/g)>shell without pyrolysis(12.1 mg/g).These activated carbons would be highly suitable in industry processes to remove phenolic contaminants.

Removal of phenol by activated carbons prepared from palm oil mill effluent sludge

The study was attempted to produce activated carbons from palm oil mill effluent （POME） sludge. The adsorption capacity of the activated carbons produced was evaluated in aqueous solution of phenol. Two types of activation were followed, namely, thermal activation at 300, 500 and 800%, and physical activation at 150% （boiling treatment）. A control （raw POME sludge） was used to compare the adsorption capacity of the activated carbons produced. The results indicated that the activation temperature of 800℃ showed maximum absorption capacity by the activated carbon （POME 800） in aqueous solution of phenol. Batch adsorption studies showed an equilibrium time of 6 h for the activated carbon of POME 800. It was observed that the adsorption capacity was higher at lower values ofpH （2--3） and higher value of initial concentration of phenol （200--300 mg/L）, The equilibrium data were fitted by the Langmuir and Freundlich adsorption isotherms. The adsorption of phenol onto the activated carbon POME 800 was studied in terms of pseudo-first and second order kinetics to predict the rate constant and equilibrium capacity with the effect of initial phenol concentrations. The rate of adsorption was found to be better correlation for the pseudo-second order kinetics compared to the first order kinetics.

Experimental and Theoretical Study of the Effect of Moisture on Methane Adsorption and Desorption by Activated Carbon at 273.5 K

Adsorption and desorption of methane by activated carbon （AC） at constant temperature and at various pressures were investigated. The effect of moisture was also studied. A volumetric method was used, up to 40 bar, at a temperature of 273.5 K. Results of a dry AC sample were compared with those obtained from a moist sample and two different ACs with different physical and surface properties were used. As expected, the results showed that the existence of moisture, trapped in the AC pores, could lead to a decrease in the amount of methane adsorbed and a decrease in the amount of methane delivered during desorption. To model the experimental results, a large variety of adsorption isotherms were used. The regressed parameters for the adsorption isotherms were obtained using the experimental data generated in the present study. The accuracy of the results obtained from the different adsorption isotherms was favorably compared.

Adsorption Characteristics of Activated Carbon Derived from Scrap Tires for Malachite Green:Influence of Small Organics

The influence of small organics on the adsorption characteristics of activated carbon produced from industrial pyrolytic tire char(APTC)for malachite green(MG) was investigated by a batch method. Phenol was chosen as the representative of small organics. The effects of phenol on adsorption equilibrium, kinetics and thermodynamics were studied systematically. The results indicate that APTC is a potential adsorbent for MG. The presence of phenol decreases the adsorption capacity of APTC for MG, but improves the rate of adsorption, while the adsorption characteristics, such as equilibrium, kinetics and thermodynamics are not affected by phenol. The adsorption equilibrium data follow Langmuir isotherm and the kinetic data are well described by the pseudo-second-order kinetic model. The adsorption process follows intra-particle diffusion model and the adsorption rate is determined by more than one process. Thermodynamic study shows that the adsorption is an endothermic and spontaneous physisorption process.

Adsorption and photocatalytic degradation of phenol over TiO_2/ACF

The adsorption and photocatalytic degradation of phenol in water were investigated in a cylindrical borosilicon glass photoreactor with a cooling water jacket using TiO 2/ACF as photocatalyst. A 15 W UV lamp(254 nm) was used as central light source. The effects of the temperature and initial concentration of phenol solution on adsorption and photocatalytic process were studied, and the comparison of adsorption, photolysis and photocatalysis was conducted. The results show that the classical model of Langmuir gives a good description of the adsorption of phenol on TiO 2/ACF and low temperature can improve the adsorption of phenol on photocatalyst; increasing temperature can increase the photocatalytic degradation rate of phenol; and the adsorption enhances the photocatalytic removal of phenol.

Phenol Removal from Water with Potassium Permanganate Modified Granular Activated Carbon

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%.

Removal of phenol by powdered activated carbon adsorption

In this study, the adsorption performance of powdered activated carbon （PAC） on phenol was investi- gated in aqueous solutions. Batch adsorption studies were performed to evaluate the effects of various experimental parameters like PAC type, PAC dose, initial solution pH, temperature and pre-oxidation on the adsorption of phenol by PAC and establish the adsorption kinetics, thermo- dynamics and isothermal models. The results indicated that PAC adsorption is an effective method to remove phenol from water, and the effects of all the five factors on adsorption of phenol were significant. The adsorption rate of phenol by PAC was rapid, and more than 80% phenol could be absorbed by PAC within the initial 10 min. The adsorption process can be well described by pseudo- second-order adsorption kinetic model with rate constant amounted to 0.0313, 0.0305 and 0.0241 mg.μg .min -1 with coal, coconut shell and bamboo charcoal. The equilibrium data of phenol absorbed onto PAC were analyzed by Langmuir, Freundlich and Tempkin adsorp- tion isotherms and Freundlich adsorption isotherm model gave the best correlation with the experimental data. Thermodynamic parameters such as the standard Gibbs free energy （△G0）, enthalpy （△H0） and entropy （△S0） obtained in this study indicated that the adsorption of phenol by PAC is spontaneous, exothermic and entropy decreasing.

Kinetics and thermodynamics of the phosphine adsorption on the modified activated carbon

The kinetics and the thermodynamics of phosphine(PH3)adsorption on the modified activated carbon have been explained for the adsorption process of PH3.This study investigated the kinetic and thermody-namic properties of PH3 adsorption on the activated carbon impregnated with 5%HCl solution.The thermodynamic properties including PH3 adsorption isotherm and adsorp-tion heat were separately investigated at 20℃,70℃,90℃.The results showed that the Freundlich-type isotherm equation described the isotherms well.The adsorption capacity increased with increasing temperature between 20℃ and 70℃.Between 70℃ and 90℃,the adsorption capacity decreased obviously with increasing temperature.The adsorption capacity reached the maximum at 70℃.By analyzing the results of the kinetics and the thermody-namics,we found that the adsorption of PH3 was dominated by physical adsorption at the lower temperature(20℃).Then with increasing temperature,chemical adsorption gradually dominated in the adsorption process.The adsorption capacity decreased at above 70℃ is due to the exothermic effects in the process of adsorption.

Effect of Granular Activated Carbon on the Enhancement of Cometabolic Biodegradation of Phenol and 4-Chlorophenol

Enhancement of the cometabolic biotransformation of 4-chlorophenol（4-cp） and phenol were studied using chemically and thermally granular activated carbons（GACs）.It was found that both chemically activated and thermally activated GAC effectively adsorb phenol and 4-cp.More than 80% adsorped substrates were later desorpted,showing a reversible sorption behaviour in the GAC.For each activated carbon type,4-cp was preferentially adsorbed over phenol and the desorption efficiencies of both phenol and 4-cp were found to increase linearly with the initial mass of adsorbate in the adsorbent.The biodegradation of 500 mg/L phenol by Pseudomonas putida took 24 h while the biodegradation of 4-cp took 32 h.Inhibitions during the cometabolic biodegradation of 4-cp and phenol were alleviated by the addition of the GACs.The system with chemically-activated coconut type GAC had better system stability over thermally-activated peat type GAC.The results show that GAC can be regenerated by the cells enhancement of the cometabolic biotransformation of 4-cp and phenol can be accomplished using chemically-activated coconut type GAC.

Activated carbons derived from oil palm empty-fruit bunches: Application to environmental problems

Activated carbons derived from oil palm empty fruit bunches （EFB） were investigated to find the suitability of its application for removal of phenol in aqueous solution through adsorption process, Two types of activation namely; thermal activation at 300, 500 and 800℃and physical activation at 150℃ （boiling treatment） were used for the production of the activated carbons. A control （untreated EFB） was used to compare the adsorption capacity of the activated carbons produced from these processes. The results indicated that the activated carbon derived at the temperature of 800℃ showed maximum absorption capacity in the aqueous solution of phenol. Batch adsorption studies showed an equilibrium time of 6 h for the activated carbon at 800℃. It was observed that the adsorption capacity was higher at lower values of pH （2-3） and higher value of initial concentration of phenol （200-300 mg/L）. The equilibrium data fitted better with the Freundlich adsorption isotherm compared to the Langmuir. Kinetic studies of phenol adsorption onto activated carbons were also studied to evaluate the adsorption rate. The estimated cost for production of activated carbon from EFB was shown in lower price （USD 0.50/kg of activated carbon） compared the activated carbon from other sources and processes.

糠醛渣活性炭对4,4′-硫代二苯酚和双酚F的吸附性能

以固废糠醛渣为原料,水蒸气活化法制备糠醛渣活性炭(FRAC),研究其对水体中4,4′-硫代二苯酚(TDP)和双酚F(BPF)的吸附性能,探讨了吸附时间、FRAC用量、pH值、温度以及TDP和BPF溶液的初始浓度对吸附过程的影响。研究结果表明:Sips和Koble-Corrigan等温模型可以很好地描述FRAC对TDP和BPF的吸附平衡数据,FRAC对TDP和BPF的吸附均是自发的放热过程。FRAC对TDP和BPF的吸附过程均符合准二级动力学模型。另外,TDP和BPF在FRAC上的吸附主要受到氢键、疏水作用、静电作用和π—π相互作用的共同影响。在298 K时,FRAC吸附TDP和BPF的最大吸附量分别为5.4083 mmol/g和3.6955 mmol/g,表明FRAC在处理内分泌干扰物废水上具有广泛的应用前景。

硝酸改性活性炭纤维对苯酚吸附性能研究

以粘胶基活性炭纤维(ACF)为吸附材料,通过硝酸改性得到ACF-1,对改性前后活性炭纤维吸附苯酚性能进行分析表征。结果表明:在酸性、中性和低温条件下利于活性炭纤维吸附苯酚,酸处理使活性炭纤维孔结构改变,表面含氧官能团增加。经过碱脱除再生3次后,ACF-1的吸附能力为初始吸附率的64.97%。吸附等温模型和动力学模型计算结果表明:准二级动力学模型和Langmuir吸附等温模型能够更好地描述活性炭纤维吸附苯酚过程。