Process Engineering

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Browsing Process Engineering by Subject "Adsorption"

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    Characterization and Optimization of Iron (III) Modified Bentonite Adsorbent for Efficient Removal of Fluoride from Aqueous Solution
    (AAU, 2018-06) Frehiwot, Tesfamariam; Zebene, Kiflie (PhD)
    The main objective of the research was to prepare Fe iv 3+ -modified bentonite clay to be used as an adsorbent by optimizing the iron three loading through batch wise variation of agitation time, adsorbent dose, and iron three concentration for efficient removal of fluoride from aqueous solution. Physicochemical characterization of raw and Fe 3+ -modified bentonite clay was done by X-ray diffraction, Fourier transformed infrared spectroscopy, Cation exchange capacity, and pHpzc. To investigate the performance of the prepared Fe 3+ -modified bentonite adsorbent the effect of contact time, adsorbate concentration, adsorbent dosage and pH were evaluated. The adsorption capacity of fluoride by Fe 3+ -modified bentonite was observed to be 3.37 mg/g at (26±2) 0 C temperature. Design-Expert 7.0.0 three-level-full factorial RSM was applied for experimental design and statistical analysis of results. A total of 32 experiments were conducted at conditions of adsorbent dosage 1, 1.5 and 2 g, initial fluoride concentration 5, 15 and 25 ppm, and 15, 30 and 45 min of contact time. From the analysis of experimental results optimum conditions for efficient removal of fluoride were obtained at 2 g adsorbent dosage, 15 ppm adsorbate concentration and 15 min contact time which resulted 99.56% F - removal. Kinetic studies revealed that fluoride adsorption fitted well to pseudo-second-order model and Freundlich adsorption isotherm. Fe 3+ -modified bentonite showed a good stability in removing fluoride from natural fluoride containing water with > 66% F - removal. The fluoride loaded adsorbent was reused and also regenerated using 0.5 M NaOH. Thus, this study has proved that Fe 3+ -modified bentonite is a promising low cost adsorbent with high adsorption capacity of fluoride and can be a candidate for conventional de-fluoridation methods.
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    Modification of Bentonite Clay for Adsorption Enhancement for Congo Red Dye Removal from Textile Waste Water
    (Addis Ababa University, 2017-11) Kiros, Fisseha; Beteley, Tekola (PhD)
    Bentonite clays are considered as low cost adsorbents due to their local and abundant availability, non-toxicity, and potential for ion exchange and can easily undergo modification to increase their surface area and adsorption capacity. The present study includes the preparation, characterization and performance testing of a set of adsorbents, prepared by the acid activation of bentonite clay obtained from Gewane, Afar regional state of Ethiopia. The acid activation experiments were carried out by sulfuric acid solutions of various concentrations in the range of (0.05-0.5 M) at different temperatures (30, 60, 90 oC) for 3hours.The result revealed that bentonite activated with 0.1M sulfuric acid at 30 oC showed a higher efficiency in removing congo red dye from aqueous solution and was selected for further investigation. The raw and acid activated bentonite materials were characterized using several techniques such as wet-chemical /complete silicate analysis , Scanning electron microscopy (SEM with EDS), Fourier-transform infrared spectroscopy (FTIR) and XRD. The results of the analysis by complete silicate analysis and Energy Dispersive Spectroscopy (EDS), showed that the presence of silica and alumina as major constituents with a very small amount of iron, calcium, magnesium, sodium, potassium, and titanium as a form of impurities. The results of the XRD showed that the raw bentonite was composed of montmorillonite, quartz, hematite, feldspar, and cristobalite. The microscopic images obtained through SEM showed that the structure of the activated bentonite was different from the raw bentonite clay indicating the formation of perforation /vacant sites. A general full factorial experimental design was employed to correlate the effect of key operational parameters, such as contact time, initial dye concentration and, pH on the adsorption of congo red dye onto bentonite activated with 0.1 M sulfuric acid were experimentally studied using a batch adsorption process. The result showed that the optimum condition for the percentage dye removal was 95.74% at the time of 6 hr. a dye concentration100.58 mg/l and pH 5.03 .The isotherm data for adsorption of congo red dye on AA bentonite were analyzed using Langmuir and Freundlich adsorption isotherms. Freundlich isotherm model was found more representative. Further to understand the adsorption kinetics the adsorption data were analyzed by pseudo first-order and pseudo second-order kinetics. The results revealed that adsorption kinetics was adequately described by pseudo second-order kinetics.
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    Optimal Removal of Methylene Blue in Aqueous Solution Using Selected Rice Husk Activated Carbon from Pore Development Agent.
    (Addis Ababa University, 2019-11) Alemie, Desalgne; Shegaw, Ahmed (PhD)
    In this study, the possible utilization of rice husk activated carbon as an adsorbent for the optimum removal of methylene blue dye from aqueous solutions has been investigated. Selective criterions for rice husk activated carbon (AC) were carried out as follows: Porous characteristics by, Brunauer-Emmett-Teller (BET) total surface area analyzer, surface structure using Scanning Electron Microscope (SEM) and surface functional group using Fourier Transform Infrared Spectroscopy (FT-IR) analysis. The batch adsorption studies of methylene blue (MB) carried out by selected porous ZnCl2 treated activated carbon. CCD at three-level and four factors were used to design the experiment to develop model equations for MB removal. The AC was initially prepared through chemical activation using zinc chloride (AC-ZC), phosphoric acid (AC-PA), and potassium hydroxide (ACPH) activating agents at optimal conditions of (carbonization temperature 500 C and holding time 60 min). The TSA were measured on BET 603 m o 2 2 /g, 545 m /g 2 and 498 m /g respectively. The optimal results in effect of process parameters of the analysis were for optimum adsorption of MB on selected porous AC-ZC 98.9 %, pH 8.69, adsorbent dose 1.9 g, and concentration of MB 11.63 g/ml and contact time 51 min. The results conclude the locally studied activated carbon of rice husk could be employed as low-cost alternatives to commercially imported activated carbon for the removal of basic dyes during wastewater treatment. This low cost and effective removal method may provide a promising solution for the removal of dye from wastewater.
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    Preparation and Characterization of Activated Carbon from Flower Waste Biomass for Methylene blue Removal
    (Addis Ababa University, 2019-11) Getu, Maru; Sintayehu, Nibret (PhD)
    Activated carbon (AC) can be used as an adsorbent to remove pollutants from waste water streams. 520 kg flower biomass waste is generated daily at a single floriculture industry in Ethiopia. Despite AC has been produced from different lignocellulosic biomass waste, utilizing Flower waste biomass (FWB) as a precursor to produce AC has an advantage of being new raw material, easily available, renewable precursor, and can be a way of reducing environmental pollution. This study presents synthesis of AC from FWB by chemical activation method using ZnCl2 and removal of methylene blue (MB) using the as-prepared AC. The parameters in the study were impregnation ratio, carbonization temperature, and carbonization time. Higher BET surface area of 750 m 2 -1 g , pore volume of 1.91 cm 3 -1 g and pore diameter of 1.89 nm was obtained at 1:1 impregnation ratio, ° 500 C carbonization temperature, and 1 hr of carbonization time. Effect of adsorption dosage, PH, initial dye concentration, and contact time on percentage removal of MB were studied. Maximum removal of MB was recorded at 0.05 g adsorbent dosage, 60 min contact time, PH of 10, and initial dye concentration of 10 mg L -1 . Kinetics and isotherm studies showed that the adsorption mechanism of MB using FWB based AC follows pseudo second order while both Langmuir and Freundlich model well fitted the adsorption data with maximum removal efficiency of 94.2% and adsorption capacity of 22.39 mg g -1 . FWB can be a good precursor for AC production and can be used to remove MB from wastewater.
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    Removal Of Arsenic(III) from Aquoes Soloutions by CarboxyMethyl Cellulose-Stabilized Nano Zero-Valent Iron
    (Addis Ababa University, 2019) Nahom, Kahsay; Hundessa, Dessalegn (PhD)
    Arsenic is the most hazardous element in the chemical world and its presence in drinking water can cause disaster. Conventional method of preparation of nano zero valent iron using physical and chemical methods normally employ toxic chemicals as reducing agents, organic solvents, or non-biodegradable stabilizing agents, and are therefore potentially dangerous to the environment and biological systems. Experiments were conducted in a batch system and the effects of pH, contact time, and the initial concentrations of Arsenic (III) and nanoscale zero valent iron doses were investigated. The nature and morphology of synthesized adsorbent were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The experimental results revealed that the removal efficiency of Arsenic (III) was increased with decreasing pH of the solution but decreased with gradual increasing of initial concentration and dosage. The removal rate of Arsenic (III) was 97.4 % at a dosage of 1.0 g, pH 2 and with 15g/L initial As(III) concentration. The experimental data was found to be well described by Langmuir model. The maximum loading capacity as estimated by Langmuir model was 116.27 mg/g. Also, the adsorption trend followed the pseudo-second order kinetics model and equilibrium was achieved in two hours. Overall, the results obtained indicate that CMC-Stabilized nZVI could be effectively used for removal of Arsenic (III) from waste water.