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1

Characterization and optimization of spectrophotometric colour removal from dye containing wastewater by Coagulation-Flocculation

Obiora-Okafo I. A., Onukwuli O. D.

Polish Journal of Chemical Technology

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2018

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Vol. 20, nr 4

49--59

EN

The performance of Vigna unguiculata coagulant (VUC) for colour removal from acid dye was investigated in this study. The proximate, structure and morphology of the coagulant were investigated using standard official methods, Fourier-Transform Infrared (FTIR) spectrometer and scanning electron microscopy (SEM), respectively. Response surface methodology (RSM) using face-centred central composite design (FCCD) optimized four process variables including pH, coagulant dosage, dye concentration and time. The colour removal efficiency obtained from the optimization analysis was 99.26% at process conditions of pH 2, coagulant dosage 256.09 mg/l, dye concentration 16.7 mg/l and time 540 min. The verification experiments agreed with the predicted values having a standard error value of 1.96%. Overlay contour plot established optimum areas where the predicted response variable is in an acceptable range (≥ 70%) with respect to optimum conditions. The FCCD approach was appropriate for optimizing the process giving higher removal efficiency when compared to the main effect plots.

2

Assessing influence of hydrochloric acid leaching on structural changes and bleaching performance of Nigerian clay from Udi

Ajemba R. O., Onukwuli O. D.

Physicochemical Problems of Mineral Processing

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2014

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Vol. 50, iss. 1

349--358

EN

Clay from Udi in Nigeria was mined, ground, and acid-leached at different concentrations of hydrochloric acid to produce adsorbents of varying properties. The raw and acid-leached samples were characterized using x-ray fluorescence (XRF) and Fourier transforms infra-red spectroscopy (FTIR) to examine the structural modifications in the clay as a result of acid-leaching. The analysis showed that the acid-leaching process caused several modifications of the clay samples. The surface area, Si/[Al + Fe + Mg] ratio, adsorption capacity were found to have increased in the acid-leached samples. The acid-leached samples were tested in order to ascertain their performance in bleaching palm oil and it was observed that the bleaching efficiency increased from 29.8% to 66.7%. The acid-leached sample prepared with 7M hydrochloric acid yielded an adsorbent that was efficient in bleaching palm oil under the experimental conditions. The isotherm analysis showed that the bleaching process followed the Freundlich equation.

3

Adsorptive removal of colour pigment from palm oil using acid activated nteje clay. Kinetics, equilibrium and thermodynamics

Ajemba R. O., Onukwuli O. D.

Physicochemical Problems of Mineral Processing

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2013

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Vol. 49, iss. 1

369--381

EN

The kinetics of colour pigment removal from palm oil using acid activated clay from Nteje has been investigated. To determine the equilibrium adsorption capacity, the effects of temperature, contact time, adsorbent dosage and particle size were studied. The experimental adsorption data were analyzed using pseudo-first order, pseudo-second order, and Elovich kinetic models. The pseudo-second order model fitted very well to the kinetic experimental data. Equilibrium isotherms were analyzed by Lang-muir and Freundlich adsorption models. The data was in line with the Freundlich isotherm indicating a monolayer adsorption. The activation energy was calculated as 12 kJ/mol, and other thermodynamic parameters were determined as ΔS° = 0.063 J/mol, ΔH° = –34.994 J/mol, and ΔG° = –58.606 kJ/mol. These values indicate that the adsorption of colour pigment from palm oil onto acid activated clay was exothermic and can be attributed to physico-chemical adsorption process.