J. C. Igwe

Adsorption kinetics and intraparticulate diffusivities of Hg, As and Pb ions on unmodified and thiolated coconut fiber

As, Hg and Pb are examples of heavy metals which are present in different types of industrial effluents responsible for environmental pollution. Their removal is traditionally made by chemical precipitation, ion-exchange and so on. However, this is expensive and not completely feasible to reduce their concentrations to the levels as low as required by the environmental legislation. Biosorption is a process in which solids of natural origin are employed for binding the heavy metal. It is a promising alternative method to treat industrial effluents, mainly because of its low cost and high metal binding capacity. The kinetics was studied for biosorption experiments using coconut fiber for As (III), Hg (II) and Pb (II) ions adsorption. The specific surface area and surface charge density of the coconut fiber are 1.186×1025 (m2/g) and 5.39 ×1024 (meq/m2), respectively. The maximum adsorption capacity was found to be the highest for Pb (II) followed by Hg (II) and As (III). The modification of the adsorbent by thiolation affected the adsorption capacity. Equilibrium sorption was reached for the metal ions at about 60 min. The equilibrium constant and free energy of the adsorption at 30 °C were calculated. The mechanism of sorption was found to obey the particle-diffusion model. The kinetic studies showed that the sorption rates could be described by both pseudo first-order and pseudo second-order models. The pseudo second-order model showed a better fit with a rate constant value of 1.16 × 10−4/min. for all three metal ions. Therefore, the results of this study show that coconut fiber, both modified and unmodified, is an efficient adsorbent for the removal of toxic and valuable metals from industrial effluents.

Equilibrium sorption isotherm studies of Cd(II), Pb(II) and Zn(II) ions detoxification from waste water using unmodified and EDTA-modified maize husk

The mobilization of heavy metals in the environment due to industrial activities is of serious concern due to the toxicity of these metals in humans and other forms of life. The equilibrium adsorption isotherms of Cd(II), Pb(II) and Zn(II) ions, detoxification from waste water using unmodified and EDTA-modified maize husk have been studied. Maize husk was found to be an excellent adsorbent for the removal of these metal ions. The amount of these metal ions adsorbed increased as the initial concentration increased. Also, EDTA-modification enhanced the adsorption capacity of maize husk due to the chelating ability of ethylenediamine tetra acetic acid (EDTA). Among the three adsorption isotherms tested, Dubinin-Radushkevich isotherm gave the best fit with R 2 value ranging from 0.7646 to 0.9988 and an average value of 0.9321. This is followed by Freundlich and then Langmiur isotherms. The sorption process was found to be mostly a physiosorption process as seen from the apparent energy of adsorption which ranged from 1.03 KJ/mol to 12.91 KJ/mol. Therefore, this study demonstrates that maize husk which is an environmental pollutant could be used to adsorb heavy metals and achieve environmental cleanliness.

Adsorption isotherm studies of Cd (II), Pb (II) and Zn (II) ions bioremediation from aqueous solution using unmodified and EDTA-modified maize cob

The need to clean-up heavy metal contaminated environment can not be over emphasized. This paper describes the adsorption isotherm studies of Cd (II), Pb (II) and Zn (II) ions from aqueous solution using unmodified and EDTA-modified maize cob. Maize cob was found to be an excellent adsorbent for the removal of these metal ions. The amount of metal ions adsorbed increased as the ini- tial concentration increased. Also, EDTA - modification enhanced the adsorption capacity of maize cob probably due to the chelating ability of EDTA. Among the three adsorption isotherm tested, Dubinin- Radushkevich gave the best fit with R2 value ranging from 0.9539 to 0.9973 and an average value of 0.9819. This is followed by Freundlich isotherm (Ave. 0.9783) and then the Langmuir isotherm (Ave. 0.7637). The sorption process was found to be a physiosorption process as seen from the apparent ener- gy of adsorption which ranged from 2.05KJ\mol to 4.56KJ\mol. Therefore, this study demonstrates that maize cob which is an environmental pollutant could be used to adsorb heavy metals and achieve cleanliness thereby abating environmental nuisance caused by the maize cob.

Multielement analyses of human scalp hair samples from three distant towns in southeastern Nigeria

Hair samples were collected from three distant towns in Southeastern Nigeria and analyzed for their contents of the trace metals, Pb, Cd, Zn, Ni, Cu, and Cr by atomic absorption spectrometry. Higher geometric mean values for Pb, Zn, Ni, Cu, and Cr were obtained in hair samples of donors from the industrialized areas, Aba and Onitsha. Higher levels of Pb and Cr were observed in hair samples of male donors while higher levels of Zn and Cu were obtained in hair samples from the unindustrialized area, Isuochi. For the general population studied, geometric mean values of 65.4 ig/g (range 9.1 to 194.5 ig/g); 1.2 ig/g (0.4 to 6.6 ig/g); 146.2 ig/g (57.7 to 510 ig/g); 26.4 ig/g (5.0 to 143.2 ig/g); 117.2 ig/g (29.4 to 363.5 ig/g); 35.1 ig/g (19.5 to 60.6 ig/g) were obtained for the metals, Pb, Cd, Zn, Ni, Cu, and Cr, respectively. Our result indicates that ~ 89% of the population had Pb levels >30 ig/g, indicative of occupational exposure, while about 20% had levels >110ig/g which is considered dangerous.

Adsorption isotherm studies of BOD, TSS and colour reduction from palm oil mill effluent (POME) using boiler fly ash

Palm oil is one of the two most important vegetable oils in the worlds oil and fats market. The extraction and purification processes generate different kinds of waste generally known as palm oil mill effluent (POME). Earlier studies had indicated the possibility of using boiler fly ash to adsorb impurities and colour in POME treatment. The adsorption treatment of POME using boiler fly ash was further investigated in detail in this work with regards to the reduction of BOD, colour and TSS from palm oil mill effluent. The amount of BOD, colour and TSS adsorbed increased as the weight of the boiler fly ash used was increased. Also, the smaller particle size of 425µm adsorbed more than the 850µm size. Attempts were made to fit the experimental data with the Freundlich, Langmuir and Dubinin-Radushkevich isotherms. The R2 values, which ranged from 0.8974-0.9898, 0.8848-0.9824 and 0.6235-0.9101 for Freundlich, Langmuir and Dubinin-Radushkevich isotherms respectively, showed that Freundlich isotherm gave a better fit followed by Langmuir and then Dubinin-Radushkevich isotherm. The sorption trend could be put as BOD > Colour > TSS. The apparent energy of adsorption was found to be 1.25, 0.58 and 0.97 (KJ/mol) for BOD, colour and TSS respectively, showing that sorption process occurs by physiosorption. Therefore, boiler fly ash is capable of reducing BOD, Colour and TSS from POME and hence could be used to develop a good adsorbent for POME treatment.

Adsorption Isotherm Studies of Ni (II), Cu (II) and Zn (II) Ions on Unmodified and Mercapto - Acetic Acid (MAA) Modified Sorghum Hulls

Aims: To compare the efficiency of Sorghum Hull of two different particle sizes, different concentrations modified with mercaptoacetic acid and the effect of each on the heavy metal removal to obtain optimum conditions for sorption process. Study Design: The concentrations of the metal ions were monitored using Atomic Absorption Spectrophotometer (AAS). Place and Duration of Study: This study was carried out at the Industrial Chemistry laboratory, Department of Pure and Industrial Chemistry, University of Port Harcourt between February and August 2013. Original Research Article Imaga et al.; IRJPAC, 5(4): 318-330, 2015; Article no.IRJPAC.2015.025 319 Methodology: The Sorghum Hulls (SH) (Sorghum bicolor) obtained from a Brewery, were washed and air dried, crushed to smaller particles and sieved to obtain particle sizes of 106 μm and 250 μm. They were activated by soaking in excess of 0.3M HNO3 solution for 24 h, filtered through a Whatman No.41 filter paper, rinsed with deionised water and air dried for 24 h. The air-dried activated sorghum hulls were divided into three parts, one part was left unmodified and the other two parts were modified by 0.5M and 1.0M mercaptoacetic acid (HSCH2COOH). Equilibrium sorption of Ni (II), Cu (II) and Zn (II) were carried out for each adsorbent (106 μm and 250 μm) at pH of 6.0 and temperature of 28°C to find the effects of initial concentration on the sorption process by preparing stock solutions of 1000 mg/L of Cu (II), Ni (II) and Zn (II) ions from CuSO4, Ni(C2H3O2)2, and ZnSO4 respectively. Working concentrations of 10, 20,30,40,50 mg/L were obtained by serial dilutions. The concentrations of these solutions were confirmed using Atomic Absorption Spectrophotometer (AAS). The difference in the metal ion concentration of the solutions before and after sorption gave the amount adsorbed by each adsorbent. Results: Sorption efficiency followed the trend Cu 2+ >Ni 2+ >Zn 2+ and Ni 2+ >Cu 2+ >Zn 2+ for 106μm and 250μm, respectively. This was influenced by factors such as ionic radii, ionic charge, hydration energy, initial metal ion concentration, contact time, adsorbate pH and extent of acid modification. Sorption capacity followed the sequence: 1.0MSH>0.5MSH>USH. Equilibrium sorption of the three metals on the adsorbents using coefficient of determination (R) showed that sorption of Zn on 250μm size and sorption of Ni 2+ on 106μm size followed Langmuir isotherm; sorption of Zn 2+ on 106μm mesh and sorption of Cu on 250μm size by Freundlich isotherm and sorption of Cu on 106μm size and sorption of Ni 2+ on 250μm mesh by Temkin isotherm. Sorption on 1.0MSH gave the highest value of constants: (qmax = 121.814 mg/l, KF = 1.5281 mg/l and bT = 0.245 kJ/mol) and (qmax = 148.932 mg/l, KF = 1.7246 mg/l and bT = 0.262 kJ/mol) for 106 μm and 250 μm size, respectively, for Langmuir, Freundlich and Temkin isotherms respectively. Conclusion: Therefore, Sorghum Hulls were found to be good adsorbent for Ni, Cu and Zn ions with mercaptoacetic acid modification increasing the sorption capacity.

Sorption kinetics and intrapaticulate diffusivity of As(III) bioremediation from aqueous solution, using modified and unmodified coconut fiber

The pollution and toxicity problems posed by arsenic in the environment have long been established. Hence, the removal and recovery remedies have been sought, bearing in mind the effi- ciency, cost effectiveness and environmental friendliness of the methods employed. The sorption kinet- ics and intraparticulate diffusivity of As (III) bioremediation from aqueous solution using modified and unmodified coconut fiber was investigated. The amount adsorbed increased as time increased, reach- ing equilibrium at about 60 minutes. The kinetic studies showed that the sorption rates could be described by both pseudo-first order and pseudo-second order process with the later showing a better fit with a value of rate constant of 1.16 x 10 -4 min-1 for the three adsorbent types. The mechanism of sorption was found to be particle diffusion controlled. The diffusion and boundary layer effects were also investigation. Therefore, the results show that coconut fiber, both modified and unmodified is an efficient sorbent for the removal of As (III) from industrial effluents with particle diffusion as the pre- dominant mechanism.