The adsorption of methylene blue (MB) from aqueous solution using a low-cost adsorbent, rejected tea (RT), has been studied by batch adsorption technique. The adsorption experiments were carried out under different conditions of initial concentration (50-500 mg/L), solution pH 3-12, RT dose (0.05-1g) and temperature (30-50 degrees C). The equilibrium data were fitted to Langmuir and Freundlich isotherms and the equilibrium adsorption was best described by the Langmuir isotherm model with maximum monolayer adsorption capacities found to be 147, 154 and 156 mg/g at 30, 40 and 50 degrees C, respectively. Three kinetic models, pseudo-first-order, pseudo-second-order and intraparticle diffusion were employed to describe the adsorption mechanism. The experimental results showed that the pseudo-second-order equation is the best model that describes the adsorption behavior with the coefficient of correlation R(2)>or=0.99. The results suggested that RT has high potential to be used as effective adsorbent for MB removal.
The pyrolysis of oil palm mesocarp fiber (OPMF) was catalyzed with a steel slag-derived zeolite (FAU-SL) in a slow-heating fixed-bed reactor at 450 °C, 550 °C, and 600 °C. The catalytic pyrolysis of OPMF produced a maximum yield of 47 wt% bio-oil at 550 °C, and the crude pyrolysis vapor (CPV) of this process yielded crude pyrolysis oil with broad distribution of bulky oxygenated organic compounds. The bio-oil composition produced at 550 °C contained mainly light and stable acid-rich carbonyls at a relative abundance of 48.02% peak area and phenolic compounds at 12.03% peak area. The FAU-SL high mesoporosity and strong surface acidity caused the conversion of the bulky CPV molecules into mostly light acid-rich carbonyls and aromatics through secondary reactions. The secondary reactions mechanisms facilitated by FAU-SL reduced the distribution of the organic compounds in the bio-oil to mostly acid-rich carbonyls and aromatic in contrast to other common zeolite.
Oil palm mesocarp fiber (OPMF) and palm frond (PF) were respectively devolatilized by pyrolysis to OPMF-oil and PF-oil bio-oils and biochars, OPMF-char and PF-char in a slow-heating fixed-bed reactor. In particular, the OPMF-oil and PF-oil were produced to a maximum yield of 48wt% and 47wt% bio-oils at 550°C and 600°C, respectively. The high heating values (HHVs) of OPMF-oil and PF-oil were respectively found to be 23MJ/kg and 21MJ/kg, whereas 24.84MJ/kg and 24.15MJ/kg were for the corresponding biochar. The HHVs of the bio-oils and biochars are associated with low O/C ratios to be higher than those of the corresponding biomass. The Fourier transform infrared spectra and peak area ratios highlighted the effect of pyrolysis temperatures on the bio-oil compositions. The bio-oils are pervaded with numerous oxygenated carbonyl and aromatic compounds as suitable feedstocks for renewable fuels and chemicals.
The liquid-phase adsorption of phenol onto coconut shell-based activated carbon, CS850A was investigated for its equilibrium studies and kinetic modeling. Coconut shell was converted into high quality activated carbon through physiochemical activation at 850 degrees C under the influence of CO(2) flow. Beforehand, the coconut shell was carbonized at 700 degrees C and the resulted char was impregnated with KOH at 1:1 weight ratio. In order to evaluate the performance of CS850A, a series of batch adsorption experiments were conducted with initial phenol concentrations ranging from 100 to 500 mg l(-1), adsorbent loading of 0.2g and the adsorption process was maintained at 30+/-1 degrees C. The adsorption isotherms were in conformation to both Langmuir and Freundlich isotherm models. Chemical reaction was found to be a rate-controlling parameter to this phenol-CS850A batch adsorption system due to strong agreement with the pseudo-second-order kinetic model. Adsorption capacity for CS850A was found to be 205.8 mg g(-1).
Bamboo, an abundant and inexpensive natural resource in Malaysia was used to prepare activated carbon by physiochemical activation with potassium hydroxide (KOH) and carbon dioxide (CO(2)) as the activating agents at 850 degrees C for 2h. The adsorption equilibrium and kinetics of methylene blue dye on such carbon were then examined at 30 degrees C. Adsorption isotherm of the methylene blue (MB) on the activated carbon was determined and correlated with common isotherm equations. The equilibrium data for methylene blue adsorption well fitted to the Langmuir equation, with maximum monolayer adsorption capacity of 454.2mg/g. Two simplified kinetic models including pseudo-first-order and pseudo-second-order equation were selected to follow the adsorption processes. The adsorption of methylene blue could be best described by the pseudo-second-order equation. The kinetic parameters of this best-fit model were calculated and discussed.
The presence of emerging contaminants (ECs) originating from pharmaceutical waste in water, wastewater, and marine ecosystems at various geographical locations has been clearly publicised. This review paper presents an overview of current monitoring data on the occurrences and distributions of ECs in coastal ecosystem, tap water, surface water, ground water, treated sewage effluents, and other sources. Technological advancements for EC removal are also presented, which include physical, chemical, biological, and hybrid treatments. Adsorption remains the most effective method to remove ECs from water bodies. Various types of adsorbents, such as activated carbons, biochars, nanoadsorbents (carbon nanotubes and graphene), ordered mesoporous carbons, molecular imprinting polymers, clays, zeolites, and metal-organic frameworks have been extensively used for removing ECs from water sources and wastewater. Extensive findings on adsorptive performances, process efficiency, reusability properties, and other related information are thoroughly discussed in this mini review.