Papers by Keyword: Isotherm

Abstract: This study reports on the development of an iron oxide-cellulose composite material for the controlled removal of 4-hydroxy-3-nitrobenzenearsonic acid (roxarsone), a model organoarsenical. Hematite (He) and a hematite-cellulose (HeCell) composite adsorbents were prepared and characterized by thermal gravimetric analysis (TGA), nitrogen adsorption, and various spectroscopic (IR, Raman, XRD, and TEM) methods. The uptake of roxarsone at ambient conditions of He and HeCell, and goethite-cellulose (GoCell) adsorbent were compared to study the factors that influence adsorption. The monolayer adsorption capacity (mmol/g) of each adsorbent are listed in parentheses, as follows: cellulose (0.028), goethite (0.0730), Hematite (0.155), 10 % Fe coated GoCell (0.0222) and 10% Fe coated HeCell (0.0873). The relatively large surface area of hematite nanoparticles (NPs) and good dispersion of these NPs onto the cellulose supports contribute to their effective adsorption of roxarsone.

Abstract: Nowadays, many studies focus only on the removal of dyes from water in single solution. In real applications the colored effluents contain more than one component to eliminate. In this study, the adsorption of two textile dyes – Red Bemacid-ETL (RB-ETL) and Bezaktiv Turquoise Blue-VG (BTB-VG) – was investigated in a binary mixture. The derivative spectrophotometry was used to determine the specific wavelength for each dye. The effect of pH, contact time and initial dye concentrations was considered. The results show that diatomite has a good potential to eliminate both of dyes simultaneously. The competitive statistical rate theory model fits the adsorption kinetic data of the binary system well. The adsorption isotherm data for both dyes is well described by multicomponent Langmuir isotherm model. A high competition effect was observed, but BTB-VG dye was more selectively adsorbed by heat treated diatomite than RB-ETL dye.

Abstract: Heavy metals are very toxic water pollutant. Their presence not only affect human beings but also animals and vegetation because of their mobility in aqueous ecosystem, toxicity and non-biodegradability [1].in the aim of removing heavy metals from aqueous solutions, an eco-friendly biosorbent was prepared from lagoon sludge by a humification process. The biosorption of Cd²⁺ and Al³⁺ ions from aqueous solutions was investigated as a function of initial pH,contact time, initial metal ions concentration, and temperature. Langmuir and Freundlich models were used to determine the sorption isotherm. Optimum pH for the removal of cadmium and aluminum was found respectively to be around 6 and 4 [2] . The equilibrium was obtained in 60 min with the pseudo-second-order kinetic model. The Langmuir model was a better fit with the experimental data for both cadmium and aluminum adsorption with a regression coefficient up to 0.99 and Q_max of 100 and 142 mg.g^-1 respectively for Cd²⁺and Al³⁺.

Abstract: In the present study, the waste shells were used as a new low cost and eco-friendly biosorbant for Orange G anionic dye removal from aqueous solutions. Experiments were conducted in batch mode, and the effect of pH of solution, contact time, and initial dye concentration. X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and ICP-MS analysis for chemical analysis were used to characterize the obtained biosorbent. The results showed that the mussel shells are composed 73% of calcite and 26% of aragonite with some traces of aluminum, magnesium, sodium, silicium and zinc. The biosorption results show that the optimal pH was around 2 for efficient Orange G biosorption. The equilibrium was attained in 60 min. The kinetic analysis showed that the pseudo-second-order model is in good agreement with the experimental data. The biosorption isotherm was well described by Langmuir isotherm model, the maximumbiosorption capacity was 1000mg/g. The thermodynamic study revealed that the biosorption of Orange G onto mussel shell is spontaneous and exothermic.

Abstract: The purpose of this study is to compare the effectiveness of a natural and / or modified kaolinite to adsorb chromium-containing aqueous effluents in its most toxic form (the hexavalent chromate ion (Cr (VI)). Adsorbant used in the present study is a kaolinite of hydrothermal origin. The modified kaolinite has been prepared by insertion of a cationic surfactant DTAC in interlayer space of this clay. The modification method is generally performed by the cation exchange reaction in the liquid state. The specific surface areas determined by nitrogen adsorption at 77 K for the two samples of kaolinite (natural and modified) are succinctly 48.75 and 63.72 m²/g. Scanning electron microscopy has shown that the used clay is in tubular form. The treatment of natural kaolin by the intercalation of cationic surfactant increased its specific surface of about 18 %. Therefore its power sorptif increased which was found by a comparative study of adsorption of Cr (VI) on natural kaolin and / or modified.

Abstract: Activated carbon has been successfully prepared from coconut shell charcoal using novel dry mechano-chemical activation with KOH and planetary ball mill. The combination of chemical activation and mechanical activation on coconut shell charcoal is found to increase its micopore volume and surface size. These increase yielded to a high adsorption capacity which was measured at 298 K and 268 K found to be 0.6 wt. % for activated carbon. The adsorption experiments were conducted using constant-volume-variable-pressure (CVVP) test. Adsorption parameters were calculated using adsorption isotherm models: Langmuir and Dubini-Asthakov models and were found in good agreement for type II adsorption phenomenon. It is also found that the adsorption capacity of activated carbon was suitable for hydrogen storage application.

Abstract: The use of cheap and eco-friendly adsorbents studied as an alternative to activated carbon for removal of dyes from wastewater is the focus of this paper. Chitosan, which was produced from food industry waste (crab shells), was synthesized, characterized and utilized as adsorbent to remove cationic dye, basic blue, from wastewater by adsorption. Characteristics of the synthesized chitosan biosorbents was established using scanning electron microscope (SEM), and Fourier Transform Infra-Red (FTIR) spectroscopy. Experiments were conducted in batch forms to investigate the effects of contact time, initial dye concentration and adsorbent dosage. Kinetic and isotherm analysis of the adsorption process were also carried out. The results obtained revealed that removal efficiency of the chitosan was increased as the contact time and chitosan biosorbent dose were increased, but a decrease with increasing initial concentration of basic dye was observed. The pseudo-second order reaction model was found to describe the biosorption process best, with chemisorption as the rate limiting step. The maximum colour removal efficiencies of chitosan at dosage of 4 g for time duration of 90 min was found to be 91.88% of the dye from a solution of 80 ppm. The pseudo-second order kinetic model was also seen to agree very well with the dynamic behaviour of the adsorption of basic blue on chitosan under different contact time, initial dye concentrations and adsorbent dosages. The dynamic behaviour of adsorption of basic blue onto chitosan has the model fitness in the following order: pseudo-second order > Elovich model > pseudo-first order. The Elovich equation was found to be the best fit equilibrium isotherm for the sorption of basic blue onto chitosan based on linearized correlation coefficient. Moreover, the equilibrium isotherm has its model fitness to be in the order of Elovich model > Langmuir model > Freundlich model.

Abstract: The potential of Empty Fruit Bunch obtained from palm oil tree as a low-cost adsorbent is a sustainable approach in wastewater treatment. The objective this study to investigate the capability of EFB for removal colour from natural rubber wastewater as well as the influence of adsorbent dosage, pH, shaking speed and contact time. The results of the analysis show that all selected factors exhibit significant effect on removal of colour. Maximum removal (87.1%) for colour was achieved at 3.5 g of adsorbent dosage, pH 7, 150 rpm of shaking speed, 120 min of contact time. The Langmuir isotherm (R² = 0.9913) described colour adsorption slightly better than the Freundlich isotherm (R² = 0.9805), suggesting a monolayer adsorption behavior of the adsorption processes

Abstract: In this study, cross-linked chitosan coated bentonite (CCB) beads were prepared as a potential adsorbent to adsorb Cu(II) from aqueous solution. As adsorption capacity was affected by several conditions such as initial Cu(II) concentrations, stirring period and temperature, these parameters were important to be investigated. Three different concentrations of Cu(II) were used in the kinetic study, which were 10, 25 and 50 mg/L. The experimental data was found fitted well with the pseudo-second-order model, an indication that chemisorption was the rate controlling mechanism. Isotherm study was done at different temperatures with concentration of Cu(II) was varied from 10 to 200 mg/L. The maximum monolayer adsorption of Cu(II) on CCB beads based on Langmuir isotherm model at 300, 310 and 320 K were 114.94, 119.05 and 77.52 mg/g, respectively. Therefore, adsorption of Cu(II) was preferred at lower temperatures. This work proved CCB beads as an effective adsorbent for fast removal of Cu(II) from wastewater solutions.

Abstract: Palm oil mill efluent (POME) is the major industrial waste water in Malaysia and Indonesia. The processing of (POME) before discharge is a major challenge to researchers. In this study, the adsorption experiment of zinc ion from (POME) produced from the processed palm oil as primary treatment has been investigated using coconut shell and cow bone activated carbon. Experiments were conducted at a fixed initial concentration, contact time, shaking speed and at different adsorbent dosage to obtain optimum condition for the uptake of zinc ion from POME. The coconut shell carbon exhibited better removal efficiency than the cow bone powder. The results obtained at fixed condition of pH 7, contact time of 105 minutes, shaking speed of 150 rpm showed more than 90% uptake for both adsorbents. The result of the adsorption study was further analyzed using Langmuir and BET model to determine the experimental isotherm. The result showed that equilibrium data fitted better with BET model for coconut shell carbon and better with Langmuir model for cow bone powder. The result of the adsorption experiments showed that heavy metal of zinc can be sufficiently reduced on both coconut shell carbon and the cow bone powder. The morphology of both adsorbents was observed using the scanning electron microscope (SEM), the pore sizes of the adsorbents supported the uptake of zinc ion from the raw POME.