Department of Chemical Sciences

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Adsorption Efficacy of Cedrela odorata Seed Waste for Dyes: Non linear Fractal Kinetics and non linear Equilibrium Studies
(Elsevier, 2016-08-15) Omorogie, Martins
Alteration of the structural and functional integrity of the aquatic ecosystems due to contamination from toxic industrial dyes warrants cost effective remedial strategies. Cedrela odorata Seed Chaff (COSC) was locally sourced, indigenous and ubiquitous. In support of this proposition, the efficacy of the COSC was assessed for the adsorption of some toxic industrial dyes, namely Methylene Blue (MB), Congo Red (CR), Methyl Violet (MV) and Methyl Orange (MO) from aqueous solutions. The microstructures of Cedrela odorata Seed Chaff (COSC) were carried out using pH of Point of Zero Charge (PZC), Specific Surface Area (SSA), Bulk Density (BD), Fourier Transform Infra Red Spectroscopy (FTIR), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM) which indicated that various organic moieties were present in COSC, which the toxic industrial dyes studied were adsorbed onto. Non linear equilibrium and non linear fractal models were used to fit experimental data. The experimental data best fit the Fritz-Schlunder four-parameter isotherm and the fractal-like pseudo-second order (three-parameter) kinetic equation. The Langmuir monolayer adsorption capacities, qmaxL of COSC for the uptake of MB, CR, MV and MO were 88.32–111.88 mg/g, 79.46–128.84 mg/g, 75.11–121.23 mg/g and 57.35–68.23 mg/g respectively as temperature increased from 298 to 318 K. The results support the use of Cedrela odorata Seed Chaff (COSC) as a cost effective material for removal of toxic industrial dye from an aquatic system. Large scale studies are required in the future to prove the efficacy of Cedrela odorata Seed Chaff (COSC) for toxic industrial dyes from varied environmental conditions.
Adsorption of Lead and Cadmium Ions from Aqueous Solutions by Tripolyphosphate-Impregnated Kaolinite Clay
(Elsevier, 2006-06) Unuabonah, Emmanuel
The pretreatment of Kaolinite clay with tripolyphosphate (TPP) increased the cation exchange capacity (CEC) of Kaolinite clay from 13.45 meq/100 g to 128.7 meq/100 g. The equilibrium adsorption capacity of TPP–Kaolinite clay for Pb2+ and Cd2+ was 126.58 mg/g and 113.64 mg/g, respectively. The presence of Na- and Ca-electrolytes and with increase in their concentrations reduced the selectivity of TPP–Kaolinite clay for Pb2+ than Cd2+. TPP–Kaolinite clay showed higher selectivity for Pb2+ in the presence of these electrolytes and at all concentrations of these electrolytes used for the study. Binary mixtures of Pb2+ and Cd2+ in various concentrations caused a decrease in the adsorption capacity of TPP–Kaolinite for either metal ion. However, this may have caused the adsorption of Cd2+ onto high energy sites on the surface of the TPP–Kaolinite clay. Non-linear Chi-square model analysis of adsorption data using Langmuir, Langmuir–Freudlich, Freudlich, Toth and Temkin isotherms reveals that the adsorption of Pb2+ and Cd2+ by TPP–Kaolinite clay were best described by the Toth and Freudlich isotherms, respectively. At low concentrations (≤500 mg/L) the adsorption of these metal ions showed better fits to the five models with Langmuir–Freudlich and Freudlich isotherms giving the best fits for Pb2+ and Cd2+, respectively.
Adsorption of Pb (II) and Cd (II) from Aqueous Solution onto Sodium Tetraborate-modified Kaolinite Clay: Equilibrium and Thermodynamic Studies
(Elsevier, 2008) Unuabonah, Emmanuel
Kaolinite clay sample obtained from Ubulu-Ukwu in Delta State of Nigeria was modified with sodium tetraborate to obtain NTB-modified kaolinite clay. XRD measurements of NTB-modified kaolinite adsorbent showed no observable change in the d-spacing of its crystal lattice. Also, the data of XRD confirmed that this kaolinite clay sample is a mixture of kaolinite and Illite clay minerals. The SEM of modified and unmodified samples showed irregular crystal structures. FTIR results proved the surface modification of the kaolinite at –Al–O and –Si–O centers. The NTB-modified adsorbent presented with broader peaks of inner –OH. Modification of kaolinite clay sample with sodium tetraborate decreased its PZC from pH 4.40 to 3.70 while its Specific Surface Area (SSA) was increased from 10.56 m2 g−1 to 15.84 m2 g−1 . Modification with sodium tetraborate reagent increased the adsorption capacity of kaolinite clay from 16.16 mg/g to 42.92 mg/g for Pb (II) and 10.75 mg/g to 44.05 mg/g for Cd (II) at 298 K. Increasing temperature was found to increase the adsorption of both metals onto both adsorbents suggesting an endothermic adsorption reaction. The simultaneous presence of electrolyte in aqueous solution with Pb and Cd (II) was found to decrease the adsorption capacity of NTB-modified adsorbent for Pb and Cd (II). Using the Pearson's Hard and Soft Lewis Acid and Base (HSAB) theory the higher selectivity of unmodified kaolinite clay adsorbent for Pb and NTB-modified kaolinite clay for Cd (II) was justified. The thermodynamic calculations for the modified kaolinite clay sample indicated an endothermic nature of adsorption (ΔHmean + 4.35 kJ mol−1 for Pb(II) and +3.79 kJ mol−1 for Cd (II)) and an increase in entropy as a result of adsorption of Pb (II) and Cd (II) (ΔSmean −21.73 J mol−1 K for Pb (II) and −18.30J mol−1 K for Cd (II)). The small positive values of free energy change (ΔGmean) indicated that the adsorption of Pb (II) and Cd (II) onto the modified adsorbent may require some small amount of energy to make it more feasible. Modeling equilibrium adsorption data obtained suggested that NTB-modified adsorbent sample has homogeneous adsorption sites and fit very well with Langmuir adsorption model. Regeneration studies suggest that ≈85% of the metals were desorbed from both adsorbents. On reuse of the adsorbents only ≈80% of metals were adsorbed. NTB-modified kaolinite clay sample show some very good potentials as a low-cost adsorbent for the adsorption of Pb (II) and Cd (II) from aqueous solutions
Adsorption of some heavy metal ions on sulfate- and phosphate-modified Kaolin
(Elsevier, 2004) Unuabonah, Emmanuel
Kaolin (bright white lumps) from Ubulu-Ukwu in Delta State of Nigeria was modified with 200 µg mL-1 of phosphate and sulphate anions to give phosphate- and sulfate-modified adsorbents, respectively. The adsorption of four metal ions (Pb2+, Cd2+, Zn2+, and Cu2+) was studied as a function of metal ions concentration. The metal ions showed stronger affinity for the phosphate-modified adsorbent with Pb2+, Cu2+, Zn2+, and Cd2+ giving an average of 93.28%, 80.94%, 68.99%, and 61.44% uptake capacity. The order of preference for the various adsorbents shown by the metal ions was as follows: Pb2+>Cu2+>Zn2+>Cd2+. Desorption studies showed that the phosphate-modified adsorbent had the highest affinity for the metal ions, followed by the sulfate-modified clay while the unmodified clay had the least affinity. The experimental data were fitted by both the Langmuir and Freundlich models
Clean Technology for Synchronous Sequestration of Charged Organic Micro-pollutant onto Microwave-assisted Hybrid Clay Materials
(Journal of Environmental Science and Pollution Research, 2020-03) Bayode, Ajibola Abiodun
The Sustainable Development Goal 6 (SDG #6) of the United Nations (UN) is hinged on the provision, availability, and sustainability of water for the global populace by 2030. In a bid to achieve this goal, the quest to seek for ubiquitous and low-cost adsorbents to treat effluents laden with industrial dyes, such as methylene blue (MB), is on the increase in recent years. Acute exposure of humans to (MB) dye causes cyanosis, necrosis, and jaundice and even leads to death. In this research, zinc-modified hybrid clay composite adsorbent (materials from kaolinite and biomass (crushed Carica papaya seeds and/or plantain peel)) was developed via microwave route. This adsorbent was characterized using field emission scanning electron microscopy (FE-SEM),Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray (EDX), and high-resolution transmission electron microscopy (HR-TEM). These characterization techniques confirmed the success achieved in doping hybrid clay with Zn. These adsorbents were used to sequester cationic dye (MB) from aqueous solutions and textile effluent under various experimental conditions. The adsorption and desorption data obtained were analyzed using various kinetic models, which are two-step kinetics, pseudo-first order, pseudo-second order, fractal kinetics, first-order desorption, second-order desorption, and modified statistical rate theory (MSRT) desorption models. Results showed that the adsorption of the dye occurred via several chemical interactions, while the latter models (for desorption) indicated that desorption occurred in two different desorption sites on the adsorbent surfaces, which showed that the adsorption of MB dye onto the adsorbents was stable without the emergence of any secondary pollution. Adsorption of MB was achieved within 15 min for aqueous solutions and 900 min for textile effluent, which is an improvement on previous results from other studies. The three adsorption-desorption cycles for MB uptake by the adsorbents showed that it is pragmatically applicable to treat textile effluents. Hence, low-cost composite adsorbents have a potential for the effective remediation of MB dye from textile effluents as this study confirmed
Clean Technology for Synchronous Sequestration of Charged Organic Micro-pollutant onto Microwave-assisted Hybrid Clay Materials
(Springer, 2020-03-01) Omorogie, Martins
The Sustainable Development Goal 6 (SDG #6) of the United Nations (UN) is hinged on the provision, availability, and sustainability of water for the global populace by 2030. In a bid to achieve this goal, the quest to seek for ubiquitous and low-cost adsorbents to treat effluents laden with industrial dyes, such as methylene blue (MB), is on the increase in recent years. Acute exposure of humans to (MB) dye causes cyanosis, necrosis, and jaundice and even leads to death. In this research, zinc-modified hybrid clay composite adsorbent (materials from kaolinite and biomass (crushed Carica papaya seeds and/or plantain peel)) was developed via microwave route. This adsorbent was characterized using field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray (EDX), and high-resolution transmission electron microscopy (HR-TEM). These characterization techniques confirmed the success achieved in doping hybrid clay with Zn. These adsorbents were used to sequester cationic dye (MB) from aqueous solutions and textile effluent under various experimental conditions. The adsorption and desorption data obtained were analyzed using various kinetic models, which are two-step kinetics, pseudo-first order, pseudo-second order, fractal kinetics, first-order desorption, second-order desorption, and modified statistical rate theory (MSRT) desorption models. Results showed that the adsorption of the dye occurred via several chemical interactions, while the latter models (for desorption) indicated that desorption occurred in two different desorption sites on the adsorbent surfaces, which showed that the adsorption of MB dye onto the adsorbents was stable without the emergence of any secondary pollution. Adsorption of MB was achieved within 15 min for aqueous solutions and 900 min for textile effluent, which is an improvement on previous results from other studies. The three adsorption-desorption cycles for MB uptake by the adsorbents showed that it is pragmatically applicable to treat textile effluents. Hence, low-cost composite adsorbents have a potential for the effective remediation of MB dye from textile effluents as this study confirmed.
Comparison of sorption of Pb2+ and Cd2+ on kaolinite clay and polyvinyl alcohol-modified kaolinite clay.
(Elsevier, 2008) Unuabonah, Emmanuel
Kaolinite clay obtained from Ubulu-Ukwu, Delta state in Nigeria was modified with polyvinyl alcohol (PVA) reagent to obtain PVA-modified Kaolinite clay adsorbent. Scanning Electron Microscopy (SEM) of the PVA-modified adsorbent suggests that Kaolinite clay particles were made more compact in nature with no definite structure. Modification of Kaolinite clay with PVA increased its adsorption capacity for 300 mg/L Pb2+ and Cd2+ by a factor of at least 6, i.e., from 4.5 mg/g to 36.23 mg/g and from 4.38 mg/g to 29.85 mg/g, respectively, at 298 K. Binary mixtures of Pb2+ and Cd2+ decreased the adsorption capacity of Unmodified Kaolinite clay for Pb2+ by 26.3% and for Cd2+ by 0.07%, respectively. In contrast, for PVA-modified Kaolinite clay, the reductions were up to 50.9% and 58.5% for Pb2+ and Cd2+, respectively. The adsorption data of Pb2+ and Cd2+ onto both Unmodified and PVA-modified Kaolinite clay adsorbents were found to fit the Pseudo-Second Order Kinetic model (PSOM), indicating that adsorption on both surfaces was mainly by chemisorption and is concentration dependent. However, kinetic adsorption data from both adsorbent generally failed the Pseudo-First order Kinetic model (PFOM) test. Extents of desorption of 91% Pb2+ and 94% Cd2+ were obtained, using 0.1 M HCl, for the Unmodified Kaolinite clay adsorbent. It was found that 99% Pb2+ and 97% Cd2+, were desorbed, for PVA-modified Kaolinite clay adsorbents within 3 min for 60 mg/L of the metal ions adsorbed by the adsorbents.
The Effect of some Operating Variables in the Adsorption of Lead and Cadmium ions unto Modified Kaolin Clay
(Elsevier: Journal of Hazardous Materials, 2005-12-15) Unuabonah, Emmanuel
Modification of kaolinite clay mineral with orthophosphate (p-modified sample) enhanced adsorption of Pb and Cd ions from aqueous solutions of the metal ions. Increasing pH of solutions of metal ions, increasing adsorbent dose and increasing concentration of metal ion, increased the adsorption of metal ions. Adsorption of both metal ions simultaneously on both unmodified and p-modified samples indicates that adsorption of one metal ion is suppressed to some degree by the other. The presence of electrolyte and their increasing concentration reduced the adsorption capacities of both unmodified and p-modified samples for the metal ions. Ca-electrolytes had more negative effect on the adsorption capacities of the adsorbents than Na-electrolytes. Ca-electrolytes reduced adsorption capacities of the adsorbents for Pb and Cd ions. From Langmuir plots it was observed that these electrolytes increased the binding energy constant of the metal ions unto the adsorbents especially on the p-modified samples. The rate of adsorption of Pb and Cd ions on p-modified adsorbent were increased and equilibrium of metal ion solution were more quickly reached (8 min for Pb ions and 12 min for Cd ions) with p-modified adsorbent as against 20 min for adsorption of both metal ions on unmodified adsorbent when 200 mg/L of metal ion solutions were used during the kinetic studies. When adsorption data were fitted against Langmuir, Freundlich, Toth and Langmuir–Freundlich isotherms, satisfactory fits were found with the Freundlich isotherm. However, at low concentration of metal ions, data also showed satisfactory fits to Langmuir isotherm.
Efficient Chromium Abstraction from Aqueous Solution Using a Low-Cost Biosorbent: Nauclea diderrichii Seed Biomass Waste
(Elsevier, 2016-01-15) Omorogie, Martins
Toxic Cr(III) which poses environmental hazard to flora and fauna was efficiently abstracted by low-cost Nauclea diderrichii seed biomass (NDS) with good sequestral capacity for this metal was investigated in this study. The NDS surface analyses showed that it has a specific surface area of 5.36 m2/g and pHpzc of 4.90. Thermogravimetric analysis of NDS showed three consecutive weight losses from 50–200C (ca. 5%), 200–400C (ca. 35%), >400C (ca. 10%), corresponding to external water molecules, structural water molecules and heat induced condensation reactions respectively. Differential thermogram of NDS presented a large endothermic peak between 20–510C suggesting bond breakage and dissociation with the ultimate release of small molecules. The experimental data showed kinetically fast biosorption with increased initial Cr(III) concentrations, indicating the role of external mass transfer mechanism as the rate controlling mechanism in this adsorption process. The Langmuir biosorption capacity of NDS was 483.81 mg/g. The use of the corrected Akaike Information Criterion tool for ranking equilibrium models suggested that the Freundlich model best described the experimental data, which is an indication of the heterogeneous nature of the active sites on the surface of NDS.
Equilibrium, Kinetic and Sorber Design Studies on the Adsorption of Aniline Blue Dye by Sodium Tetraborate-modified Kaolinite Clay adsorbent.
(Elsevier: Journal of Hazardous Materials, 2008-01) Unuabonah, Emmanuel
Raw Kaolinite clay obtained Ubulu-Ukwu, Delta State of Nigeria and its sodium tetraborate (NTB)-modified analogue was used to adsorb Aniline blue dye. Fourier transformed infrared spectra of NTB-modified Kaolinite suggests that modification was effective on the surface of the Kaolinite clay with the strong presence of inner –OH functional group. The modification of Kaolinite clay raised its adsorption capacity from 1666 to 2000 mg/kg. Modeling adsorption data obtained from both unmodified and NTB-modified Kaolinite clay reveals that the adsorption of Aniline blue dye on unmodified Kaolinite clay is on heterogeneous adsorption sites because it followed strongly the Freundlich isotherm equation model while adsorption data from NTB-modified Kaolinite clay followed strongly the Langmuir isotherm equation model which suggest that Aniline blue dye was adsorb homogeneous adsorption sites on the NTB-modified adsorbent surface. There was an observed increase in the amount of Aniline blue adsorbed as initial dye concentration was increased from 10 to 30 mg/L. It was observed that kinetic data obtained generally gave better robust fit to the second-order kinetic model (SOM). The initial sorption rate was found to increased with increasing initial dye concentration (from 10 to 20 mg/L) for data obtained from 909 to 1111 mg kg−1 min−1 for unmodified and 3325–5000 mg kg−1 min−1 for NTB-modified adsorbents. Thereafter there was a decrease in initial sorption rate with further increase in dye concentration. The linearity of the plots of the pseudo-second-order model with very high-correlation coefficients indicates that chemisorption is involved in the adsorption process. From the design of a single-batch adsorber it is predicted that the NTB-modified Kaolinite clay adsorbent will require 50% less of the adsorbent to treat certain volumes of wastewater containing 30 mg/L of Aniline blue dye when it is compared with the unmodified adsorbent. This will be cost effective in the use of NTB-modified adsorbent for the adsorption of Aniline blue dye from water and wastewater.
Hybrid Materials from Agro-waste and Nanoparticles: Implications on the Kinetics of the Adsorption of Inorganic Pollutants
(Taylor and Francis, 2014-03-01) Omorogie, Martins
This study is a first-hand report of the immobilization of Nauclea diderrichii seed waste biomass (ND) (an agro-waste) with eco-friendly mesoporous silica (MS) and graphene oxide–MS (GO + MS) nanoparticles, producing two new hybrid materials namely: MND adsorbent for agro-waste modified with MS and GND adsorbent for agro-waste modified with GO + MS nanoparticles showed improved surface area, pore size and pore volume over those of the agro-waste. The abstractive potential of the new hybrid materials was explored for uptake of Cr(III) and Pb(II) ions. Analysis of experimental data from these new hybrid materials showed increased initial sorption rate of Cr(III) and Pb(II) ions uptake. The amounts of Cr(III) and Pb(II) ions adsorbed by MND and GND adsorbents were greater than those of ND. Modification of N. diderrichii seed waste significantly improved its rate of adsorption and diffusion coefficient for Cr(III) and Pb(II) more than its adsorption capacity. The rate of adsorption of the heavy metal ions was higher with GO + MS nanoparticles than for other adsorbents. Kinetic data were found to fit well the pseudo-second-order and the diffusion–chemisorption kinetic models suggesting that the adsorption of Cr(III) and Pb(II) onto these adsorbents is mainly through chemisorption mechanism. Analysis of kinetic data with the homogeneous particle diffusion kinetic model suggests that particle diffusion (diffusion of ions through the adsorbent) is the rate-limiting step for the adsorption process.
Kinetic and Thermodynamics of the Removal of Zn2+ and Cu2+ from Aqueous Solution by Sulphate and Phosphate Modified Bentonite Clay
(Elsevier, 2010) Unuabonah, Emmanuel
The modification of pristine Bentonite clay with sulphate and phosphate anions was found to increase its cation-exchange capacity (CEC), adsorption capacity and overall pseudo-second order kinetic rate constant for the adsorption of Cu2+ and Zn2+. Modification with sulphate and phosphate anion decreased the specific surface area of pristine Bentonite clay. Phosphate-modified Bentonite clay was found to give the highest adsorption capacity for both metal ions. The adsorption process was observed to be endothermic and spontaneous in nature for both metal ions with Zn2+ being more adsorbed. Modification with phosphate anion increased the spontaneity of the adsorption process. The effective modification of pristine Bentonite clay with sulphate anion was confirmed from hypochromic shifts in the range of 13–18 cm−1 which is typical of physisorption while modification with phosphate anion was confirmed by its hyperchromic shifts typical of chemisorption in the infrared red region using Fourier transformed infrared spectroscopy (FTIR). Using the model efficiency indicator, kinetic data were found to show very strong fit to the pseudo-second order kinetic model implying that the adsorption of Cu2+ and Zn2+ were basically by chemisorption.
Microwave-synthesized and Fenton-functionalized Pinus sylvestris Bark Activated Carbon/Metal Oxides for the Effective Uptake of Tetracycline and Congo Red Dye
(Springer, 2020-11-27) Omorogie, Martins
The quest for the accessibility to clean water all over the world has become a serious global challenge that threatens the survival of humans and the ecosystem as well. This has necessitated the need for the United Nations (UN) to highlight the provision and sustainability of clean water to the global populace as the sixth sustainable development goal (SDG) by the year 2030. In this vein, this global urge has spurred us to synthesize functionalized Pinus sylvestris bark activated carbon/metal oxides by microwave and Fenton technologies, for the removal of tetracycline and Congo red from aqueous solutions. These surfaces of the functionalized P. sylvestris bark activated carbon/metal oxides were characterized by Fourier-transform infrared spectrometry, thermogravimetry, field emission scanning electron microscopy, and the multi-point nitrogen adsorptiometry–desorptiometry, applying the Brunauer–Emmett–Teller and Barett–Joyner–Halenda techniques, which showed that diverse functional moieties were responsible for the uptake of tetracycline and Congo red from aqueous solutions. The experimental data best fit the pseudo-second order and Liu isotherm models, with a monolayer adsorption, qmaxLiu of 148.253 mg g−1 for tetracycline and 127.221 mg g−1 for Congo red at 328 K. Thermodynamic studies revealed that all the adsorption reactions were spontaneous. These adsorbents showed promising potential for the cleanup of water and wastewaters with pharmaceuticals and industrial dyes matrix.
Modeling of Fixed-bed Column Studies for the Adsorption of Cadmium onto Novel Polymer–clay Composite Adsorbent.
(Elsevier, 2010-03) Unuabonah, Emmanuel
Kaolinite clay was treated with polyvinyl alcohol to produce a novel water-stable composite called polymer–clay composite adsorbent. The modified adsorbent was found to have a maximum adsorption capacity of 20,400 ± 13 mg/L (1236 mg/g) and a maximum adsorption rate constant of ≈7.45 × 10−3 ± 0.0002 L/(min mg) at 50% breakthrough. Increase in bed height increased both the breakpoint and exhaustion point of the polymer–clay composite adsorbent. The time for the movement of the Mass Transfer Zone (ı) down the column was found to increase with increasing bed height. The presence of preadsorbed electrolyte and regeneration were found to reduce this time. Increased initial Cd2+ concentration, presence of preadsorbed electrolyte, and regeneration of polymer–clay composite adsorbent reduced the volume of effluent treated. Premodification of polymer–clay composite adsorbent with Caand Na-electrolytes reduced the rate of adsorption of Cd2+ onto polymer–clay composite and lowered the breakthrough time of the adsorbent. Regeneration and re-adsorption studies on the polymer–clay composite adsorbent presented a decrease in the bed volume treated at both the breakpoint and exhaustion points of the regenerated bed. Experimental data were observed to show stronger fits to the Bed Depth Service Time (BDST) model than the Thomas model.
Occurrence and Management of Selenium Oxyanions in Water
(Springer Nature, 2021-07) Bayode, Ajibola Abiodun
Selenium is a metalloid and an essential micronutrient needed by animals and humans at low concentrations but extremely toxic at high concentrations. It is found in the natural environment and can be present in soil, food, air, plant, and water. The chemistry of Se is linked to its different chemical forms. Se mobility and toxicity are strongly dependent on its redox state; from highly soluble oxyanions like selenate, selenite, and hydroselenite to elemental Se. However, selenate and selenite are the two predominant Se species in the water system because of their high solubility and low adsorption by sediments and soil. This provides most techniques the platform to focus on the removal of both selenite and selenate among other Se species. This chapter is focused on the occurrence and effective management of Selenate and Selenite in water.
Optimization of Kinetic Data for Two-Stage Batch Adsorption of Pb(II) Ions onto Tripolyphosphate-Modified Kaolinite Clay.
(Society of Chemical Industry, 2009) Unuabonah, Emmanuel
Most adsorption studies consider only the adsorption of pollutants ontolow cost adsorbentswithout considering how equilibrium and kinetic data can be optimized for the proper design of adsorption systems. This study considers the optimization of kinetic data obtained for the removal of Pb(II) from aqueous solution by a tripolyphosphate modified kaolinite clay adsorbent. Modification of kaolinite clay with pentasodium tripolyphosphate increases its cation adsorption capacity (CEC) and specific surface area (SSA) from 7.81 to 78.9 meq (100 g)−1 and 10.56 to 13.2 m2 g−1 respectively. X-ray diffraction patterns for both unmodified and tripolyphosphate-modified kaolinite clay suggest the modification is effective on the surface of the clay mineral. Kinetic data from the batch adsorption of Pb(II) onto the tripolyphosphate-modified kaolinite clay adsorbent were optimized to a two-stage batch adsorption of Pb(II) using the pseudo-second-order kinetic model. Mathematical model equations were developed to predict the minimum operating time for the adsorption of Pb(II). Results obtained suggest that increasing temperature and decreasing percentage Pb(II) removal by the adsorbent enhanced operating time of the adsorption process. The use of two-stage batch adsorption reduces contact time to 6.7 min from 300 min in the single-stage batch adsorption process for the adsorption of 2.5 m3 of 500 mg L−1 Pb(II) under the same operating conditions. Results show the potential of a tripolyphosphate-modified kaolinite clay for the adsorption of Pb(II) from aqueous solution and the improved efficiency of a two-stage batch adsorption process for the adsorption of Pb(II) even at increased temperature.
Oxygen Deficiency Induction and Boundary Layer Modulation for Improved Adsorption Performance of Titania Nanoparticles
(Springer, 2022-02-28) Omorogie, Martins
The use of titania (TiO2) nanoparticles as adsorbents for the adsorption of organic pollutants has attracted the attention of researchers over the years due to their stability, innocuousness, and economic cost. However, their adsorption performance has been limited, and various strategies are being explored to improve this. Herein, we demonstrated the induction of oxygen deficiency and modulation of the boundary layer of TiO2 through high-temperature treatment as a strategy for enhancing its adsorption performance. The high-temperature-treated samples denoted that HT-TiO2 was prepared by subjecting commercial Degussa P25 TiO2 to calcination at 700 ℃ for 2 h. Pristine samples designated Pr-TiO2 was utilized for comparison. The morphology, crystallinity, bulk elemental composition, and surface area of the samples were investigated using scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), electron diffraction spectroscopy (EDS), and Brunauer–Emmett–Teller (BET), respectively. Except for the morphology and porosity (obtained from nitrogen adsorption–desorption isotherm), both samples displayed varying characteristics. Experimental results reveal better adsorption performance of metronidazole (MNZ) on HT-TiO2 (qmax = 25.6937 mg/g) compared to Pr-TiO2 (qmax = 17.9856 mg/g). This phenomenon is attributed to oxygen deficiency and a smaller boundary layer on HT-TiO2 deduced from the EDS and intraparticle diffusion model.
The Sequestral Capture of Fluoride, Nitrate and Phosphate by Metal-doped and Surfactant-modified Hybrid Clay Materials
(Springer, 2018-03-02) Omorogie, Martins
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 (PO4 3−). 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 PO4 3− 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 PO4 3− 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.
The Sequestral Capture of Fluoride, Nitrate and Phosphate by Metal-doped and Surfactant-modified Hybrid Clay Materials
(Journal of Environmental Science and Pollution Research, 2018) Bayode, Ajibola Abiodun
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.
The Sequestral Capture of fluoride, nitrate and phosphate by metal-doped and surfactant-modified Hybrid Clay Materials
(Chemical Papers, Springer, 2017) Alfred, Moses Oladele
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 FeVHYCA 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,N0,N0-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.

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