Augustine E. Ofomaja

Intraparticle diffusion process for lead(II) biosorption onto mansonia wood sawdust

The overall biosorption rate of lead(II) onto mansonia wood sawdust has been determined. Kinetic modeling revealed that pseudo-second-order kinetics described the experimental data fully while pseudo-first kinetics followed for only 5 min. Ion-exchange constant, S, was similar to the pseudo-first-order rate constant, k(1), indicating that ion-exchange is important only in the first 5 min. Intraparticle diffusion increased with lead(II) concentration while film and pore diffusion decreased. The initial biosorption factor, R(i), showed that initial biosorption was intermediate. Addition of calcium ions reduced initial biosorption almost completely, reduced the amounts of lead(II) removed and increased ion-exchange phenomenon indicating significance of ion-exchange. Increase in temperature was found to increase intraparticle diffusion rate and reduce film and pore diffusion. Activation energy of film diffusion and pseudo-second-order kinetics were highest indicating that film diffusion-controlled the overall rate with active participation of ion-exchange from pseudo-second-order model.

Competitive modeling for the biosorptive removal of copper and lead ions from aqueous solution by Mansonia wood sawdust

Mansonia wood sawdust is applied as a biosorbent for the removal of copper and lead ions from single and binary aqueous solution. The effect of solution pH, electrolyte, metal ion competition and temperature were examined to obtain insight of its application for industrial waste water treatment. The Langmuir isotherm provided a better fit to experimental data for lead ion sorption with a higher monolayer capacity, while copper ion sorption was best described by the Freundlich and BET isotherms. The combined effect of adsorbing one metal ion in the presence of the other metal ion reduced the adsorption capacity of either metal ion. In a binary solution, removal of lead ions in the presence of copper ions followed the Langmuir isotherm model while the removal of copper ions in presence of lead ions followed both the Langmuir and BET isotherm models.

Removal of copper(II) from aqueous solution by pine and base modified pine cone powder as biosorbent.

Pine cone, a popular agricultural waste in South Africa has been studied for its potential application as a biosorbent in its raw and sodium hydroxide modified form. Surface modification were carried out using sodium hydroxide solution of concentration ranging from 0.01 to 0.15 mol L(-1)and the samples characterized. Batch kinetics were carried out on the biosorption of copper(II) from aqueous solution using the prepared samples and varying biosorption parameters such as solution pH, dose and biosorption temperature. The results revealed that pine cone surface was modified by sodium hydroxide treatment, carboxylic and phenolic functional groups were mostly affected as seen from Boehms titration and FTIR analysis. Surface modification reduced pH(PZC) from 7.49 to 2.55 and also increased the internal surface of pine cone powder. Copper(II) biosorption studies revealed that optimum solution pH and biosorbent dose for copper(II) removal was pH 5 and 8.0g L(-1), for the untreated and treated samples. Copper(II) uptake followed the pseudo-second order kinetic model and the intraparticle diffusion model. Copper(II) removal increased with NaOH modification and higher NaOH concentration. Biosorption temperature was found to increase copper(II) uptake for all samples indicating that copper(II) biosorption is endothermic in nature. Activation energy computed from the pseudo-second order rate constant increased with NaOH modification from 18.22 to 21.39 kJ mol(-1). The thermodynamic parameters of activation (DeltaG*, DeltaH* and DeltaS*) were computed using Erying equation and the results show that the reorientation step is mostly entropy controlled at the activation state and the contribution of entropy to the reorientation step of activation tends to decrease with NaOH washing and with increase in NaOH concentration.

Biosorption of copper(II) and lead(II) onto potassium hydroxide treated pine cone powder

Pine cone powder surface was treated with potassium hydroxide and applied for copper(II) and lead(II) removal from solution. Isotherm experiments and desorption tests were conducted and kinetic analysis was performed with increasing temperatures. As solution pH increased, the biosorption capacity and the change in hydrogen ion concentration in solution increased. The change in hydrogen ion concentration for lead(II) biosorption was slightly higher than for copper(II) biosorption. The results revealed that ion-exchange is the main mechanism for biosorption for both metal ions. The pseudo-first order kinetic model was unable to describe the biosorption process throughout the effective biosorption period while the modified pseudo-first order kinetics gave a better fit but could not predict the experimentally observed equilibrium capacities. The pseudo-second order kinetics gave a better fit to the experimental data over the temperature range from 291 to 347 K and the equilibrium capacity increased from 15.73 to 19.22 mg g(-1) for copper(II) and from 23.74 to 26.27 for lead(II). Activation energy was higher for lead(II) (22.40 kJ mol(-1)) than for copper(II) (20.36 kJ mol(-1)). The free energy of activation was higher for lead(II) than for copper(II) and the values of DeltaH* and DeltaS* indicate that the contribution of reorientation to the activation stage is higher for lead(II) than copper(II). This implies that lead(II) biosorption is more spontaneous than copper(II) biosorption. Equilibrium studies showed that the Langmuir isotherm gave a better fit for the equilibrium data indicating monolayer coverage of the biosorbent surface. There was only a small interaction between metal ions when simultaneously biosorbed and cation competition was higher for the Cu-Pb system than for the Pb-Cu system. Desorption studies and the Dubinin-Radushkevich isotherm and energy parameter, E, also support the ion-exchange mechanism.

Equilibrium studies of copper ion adsorption onto palm kernel fibre.

The equilibrium sorption of copper ions from aqueous solution using a new adsorbent, palm kernel fibre, has been studied. Palm kernel fibre is obtained in large amounts as a waste product of palm oil production. Batch equilibrium studies were carried out and system variables such as solution pH, sorbent dose, and sorption temperature were varied. The equilibrium sorption data was then analyzed using the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherms. The fit of these isotherm models to the equilibrium sorption data was determined, using the linear coefficient of determination, r(2), and the non-linear Chi-square, chi(2) error analysis. The results revealed that sorption was pH dependent and increased with increasing solution pH above the pH(PZC) of the palm kernel fibre with an optimum dose of 10g/dm(3). The equilibrium data were found to fit the Langmuir isotherm model best, with a monolayer capacity of 3.17 x 10(-4)mol/g at 339K. The sorption equilibrium constant, K(a), increased with increasing temperature, indicating that bond strength between sorbate and sorbent increased with temperature and sorption was endothermic. This was confirmed by the increase in the values of the Temkin isotherm constant, B(1), with increasing temperature. The Dubinin-Radushkevich (D-R) isotherm parameter, free energy, E, was in the range of 15.7-16.7kJ/mol suggesting that the sorption mechanism was ion exchange. Desorption studies showed that a high percentage of the copper was desorbed from the adsorbent using acid solutions (HCl, HNO(3) and CH(3)COOH) and the desorption percentage increased with acid concentration. The thermodynamics of the copper ions/palm kernel fibre system indicate that the process is spontaneous and endothermic.

The grafting of acrylic acid onto biosorbents: Effect of plant components and initiator concentration

Acrylic acid was grafted onto raw and Fentons reagent treated pine cone using KMnO4 as initiator to determine the effect of plant organic components on grafting process. Concentration of the KMnO4 was varied between 0.0005 and 0.0200 mol/dm(3) and progress of the initiation process monitored using ORP and change in hydrogen ion concentration (ΔH(+)). The optimum ratio for Fentons modification was Fe(2+)/H2O2=1/50 which corresponds to the highest leaching of plant components and having the least bulk density, ORP and ΔH(+). It was observed that increasing KMnO4 concentration, reduced the MnO2 deposited on the pine surface, increased Mn(3+) production in bulk solution while reducing grafting efficiency but increasing homopolymer formation. Radical formation on the raw pine cone was found to be lower as seen from the lower ORP and ΔH(+) values observed at similar grafting conditions. Plant organic components was observed to affect the grafting efficiency and monomer conversion as observed from the weight increase, surface charge and FTIR analysis of the acrylic acid grafted Fentons reagent treated pine and the raw pine. Optimum dye removal did not correspond to highest grafting efficiency.

Chromium (VI) ion adsorption by grafted cross-linked chitosan beads in aqueous solution – a mathematical and statistical modeling study

ABSTRACT Chitosan outstanding qualities and efficient way of binding metal ions even to near zero concentration is the major reason for special attention. Modification of chitosan allows the polymer to be applied in numerous field of research. Depending on the modification techniques, chitosan possesses increased adsorption capacity. In this study chitosan beads (CS) were formulated from chitosan flakes, the beads were cross-linked with glutaraldehyde and thereafter grafted with ethyldiaminetetraacetic acid. The stability and amine concentration of the beads were determined. The chemical functionalities of the beads were obtained by Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis (TGA). However, in the adsorption studies with Cr(VI), the number of runs in the experiment was obtained by response surface methodology (RSM), and the maximum adsorption capacity (Qm) from each run was determined from the Langmuir model. The results of the experiment showed that the non-modified beads were soluble at pH 1–4 and insoluble at pH 5, while the modified beads were insoluble at pH 1–6. The amine concentration of CS, CCS and grafted cross-linked chitosan beads (GCCS) were 4.4, 3.8 and 5.0 mmol/g, respectively. The point of zero charge (pHPZC) of GCCS was found to be 4.4. The quadratic model was significant and adequate in describing the experimental data. The difference between experimental and predicted Qm was negligible. From the design matrix and results, increased Qm was achieved at pH 5, contact time 70 min, temperature 45°C, adsorbent dosage 5 g and initial concentration 70 mg/l. The desorption of the beads loaded with Cr(VI) was successful with 0.5 M HCl eluant and contact time of 180 min, leading to cost minimization.

Successful scale-up performance of a novel papaya-clay combo adsorbent: up-flow adsorption of a basic dye

AbstractA novel low-cost papaya-clay combo adsorbent, hybrid clay (HYCA), was prepared from a combination of Carica papaya seeds and Kaolinite clay. HYCA breakthrough adsorption capacity was 35.46 mg/g for the adsorption of methylene blue (MB) dye in a pilot-scale fixed-bed reactor. In ca. 20 min, regeneration of MB dye-loaded HYCA reached at least 90% each cycle for five regeneration cycles. However, above 40°C, the HYCA adsorbent lost more than 50% of its adsorption capacity after five regeneration cycles. The AdDesignSTM software was used to successfully predict the breakthrough curve and scale-up performance of MB dye adsorption onto the HYCA adsorbent. The pore and surface diffusion model (PSDM) described experimental data better than the constant pattern homogeneous surface diffusion model. From economic assessment using the PSDM, the AdDesignSTM software predicted that 1 kg of HYCA can effectively treat 1.45 m3 (0.29 m3 each cycle) of water containing 1 mg/L of MB dye (with a treatment objective of...

Response surface methodology, central composite design, process methodology and characterization of pyrolyzed KOH pretreated environmental biomass: mathematical modelling and optimization approach

This research interestingly revealed findings from microwave carbonization of KOH pretreated pine biomass (pine bark) by the application of response surface methodology (RSM) and central composite design (CCD) experimental design and optimization tool. The activated carbons synthesized under various conditions, via the use of RSM and CCD gave high microporosity, low mesoporosity and relatively large surface areas. Their surface microstructures were studied by Fourier transform infra red spectrometry, thermogravimetric analysis, field emission scanning electron microscopy, energy dispersive analysis of X-ray and nitrogen sorptometry–desorptometry. This work provides a synthesis route for cheap activated carbons for various industrial and other scale-up applications.

Facile microwave synthesis of pine cone derived C-doped TiO2 for the photodegradation of tetracycline hydrochloride under visible-LED light

Pine cone derived carbon was doped into TiO2 via a facile microwave procedure at different powers, different from other conventional synthesis methods. The materials were adequately characterized and applied in the photodegradation of 5 mg/L tetracycline hydrochloride (TA) under visible-LED light. The XRD results showed that all materials exist as both anatase and rutile phase. However, both the microwave power and the carbon content of the composite material inhibited the conversion of anatase into rutile. The composite material synthesized at a microwave power of 800 W (CT800), displayed the highest band gap energy (3.14 eV) but showed the least electron-hole recombination rate. Hence, CT800 exhibited the highest apparent rate constant of 9.9 × 10-3 min-1 and a half-life of 70 min. An inverse relationship between OH• radical scavenger (isopropanol) and the percentage degradation by CT800 suggests that OH• is majorly responsible for the degradation of TA. Recyclability studies revealed that after 4 cycles of photocatalytic degradation reactions, CT800 retained approximately 83% performance confirming its stability and reusability.