Eliazer B. Naidoo

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.

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.

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.

Ultrasonic degradation of aqueous phenolsulfonphthalein (PSP) in the presence of nano-Fe/H 2 O 2

In this study, nano iron (nano-Fe) was successfully synthesized by sodium borohydride reduction of ferric chloride solution to enhance the ultrasonic degradation of phenolsulfonphthalein (PSP). The nano-Fe was characterized by scanning electron microscopy - energy dispersive spectroscopy (SEM-EDX), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), attenuated total reflection - Fourier transform infrared spectroscopy (ATR-FTIR), and Brunauer, Emmett and Teller (BET) surface area determination. Experimental results demonstrated that a combined ultrasonic/nano-Fe/H2O2 system was more effective for PSP removal in combination than they were individually and there was a significant difference between the combined and single processes. The ultrasonic/nano-Fe/H2O2 degradation follows the Langmuir-Hinshelwood (L-H) kinetic model. The addition of nano-Fe and H2O2 to the ultrasonic reactor greatly accelerated the degradation of PSP (25 mg/L) from 12.5% up to 96.5%. These findings indicated that ultrasonic degradation in the presence of nano-Fe and H2O2 is a promising and efficient technique for the elimination of emerging micropollutants from aqueous solution.

The sequestral capture of fluoride, nitrate and phosphate by metal-doped and surfactant-modified hybrid clay materials

Toxic anions removal for increased access to potable water remains a problem that has not been adequately addressed. This study, reports the successful preparation and modification of kaolinite-papaya seed based adsorbents under vacuum (VHYCA) for the removal of Nitrate (NO3−), Fluoride (F−) and Phosphate (PO43−). Modified adsorbents via metal-doping using Zinc were more efficient in removing these anions from aqueous solution compared with surfactant-modified adsorbents. However, both type of adsorbents showed a higher preference for NO3− removal with Zn-VHYCA and Fe-VHYCA adsorbents having 98 and 85% removal of the anion from aqueous solution, respectively. The removal of F− and PO43− was best achieved by Ortho-phenylenediamine (OP) and N,N,N′,N′-Tetramethyl-1,4-phenyldiaminedihydrochloride (TPD) modified VHYCA, respectively. However, Zn-VHYCA adsorbent showed comparable results with TPD-VHYCA in the removal of PO43− from aqueous solution. Overall, the metal-doped hybrid clay adsorbents showed better efficiency for the removal of anions than the surfactant-modified hybrid clay adsorbents.

Nano-TiO2, ultrasound and sequential nano-TiO2/ultrasonic degradation of N-acetyl-para-aminophenol from aqueous solution

The application of nano-TiO2 as adsorbent combined with ultrasound for the degradation of N-acetyl-para-aminophenol (AAP) from aqueous solution was investigated. The nano-TiO2 was characterized by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). Experimental results revealed that the adsorption of AAP by nano-TiO2 fitted the pseudo-second-order kinetic model, the equilibrium could be explained by the Freundlich isotherm and the treatment process is exothermic. The optimum removal efficiency of AAP (128.89 mg/g (77.33%)) was achieved at pH 4 when 0.03 g of nano-TiO2 was mixed with 50 mL of 100 mg/L AAP aqueous solution at ambient temperature, 60 min contact time, and a stirring speed of 120 rpm. Ultrasound at 20 kHz and pH 3 was favorable and it resulted in 52.61% and 57.43% removal efficiency with and without the addition of nano-TiO2, respectively. The degradation of AAP by ultrasound followed by nano-TiO2 treatment resulted in approximately 99.50% removal efficiency. This study showed that a sequential ultrasound and nano-TiO2 treatment process could be employed for the removal of AAP or other emerging water and wastewater contaminants.

Removal of Ni(II) and Co(II) from Aqueous Solution Using Pine Cone: A Mechanism Study

This study examines the uptake mechanism of pine cone for the removal of nickel and cobalt from aqueous solution. Surface characteristics of pine cone powder were analysed by Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). To explain the mechanism of adsorption, change in solution pH and adsorption isotherms were applied. Increasing solution pH led to increased Ni(II) and Co(II) uptake with Ni(II) being more adsorbed. Adsorption capacities correlated well with change in solution hydrogen ion concentration when solution pH was varied between 3 and 8 and metal ion concentrations were varied between 5 and 150 mg/dm3. FTIR analysis before and after adsorption showed C=O, C–O and phenolic-OH peaks changed in intensity and shifted in position. Dubinin–Radushkevich isotherm better fitted the experimental data than the Temkin isotherm. The affinities of the metals for functional groups on pine cone depended on ionic radius, surface precipitation complexes and covalent bond strength. The equilibrium binding constants increased with temperature, while heat of biosorption decreased with temperature suggesting biosorbent–biosorbate interaction effect. Desorption studies confirmed the ion-exchange mechanism. It was observed that Ni(II) showed stronger ion-exchange properties than Co(II) biosorption.