Bamidele I. Olu-Owolabi

Phytoremediation potential of Eichornia crassipes in metal-contaminated coastal water

The potential of Eichornia crassipes to serve as a phytoremediation plant in the cleaning up of metals from contaminated coastal areas was evaluated in this study. Ten metals, As, Cd, Cu, Cr, Fe, Mn, Ni, Pb, V and Zn were assessed in water and the plant roots and shoots from the coastal area of Ondo State, Nigeria and the values were used to evaluate the enrichment factor (EF) and translocation factor (TF) in the plant. The critical concentrations of the metals were lower than those specified for hyperaccumulators thus classifying the plant as an accumulator but the EF and TF revealed that the plant accumulated toxic metals such as Cr, Cd, Pb and As both at the root and at the shoot in high degree, which indicates that the plant that forms a large biomass on the water surface and is not fed upon by animals can serve as a plant for both phytoextraction and rhizofiltration in phytoremediation technology.

Modeling of fixed-bed column studies for the adsorption of cadmium onto novel polymer-clay composite adsorbent.

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 approximately = 7.45x10(-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 (delta) 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 Cd(2+) 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 Ca- and Na-electrolytes reduced the rate of adsorption of Cd(2+) 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.

Synthesis of covalently bonded graphene oxide–iron magnetic nanoparticles and the kinetics of mercury removal

Synergistically combined nanomaterials have been applied in various fields in materials science to improve the properties of nanocomposites. However, limited studies focus on the ability of such composites for water treatment. A graphene oxide (GO)–iron oxide (Fe3O4) magnetic nano-particle composite (GOMNP) was synthesized and used to study the Hg2+ adsorption kinetics from aqueous solution at various temperatures. GO was attached to magnetic nanoparticles via the amine group of 3-aminopropyltriethoxysilane which was attached the surface of Fe3O4. The GOMNP nano-composite had a Hg2+ adsorption capacity of 16.6 mg g−1. IR spectra analysis showed that hydroxyl and carboxylate functional groups were mainly responsible for Hg2+ adsorption. Adsorption of Hg2+ by the GOMNP obeyed different adsorption mechanisms at varying adsorption temperatures. The Elovich kinetics model described the Hg2+ adsorption data better than any of the other three models tested. The GOMNP nano-composite is thus a promising nanosorbent for Hg2+ removal from aqueous solutions.

Kinetic and thermodynamics of the removal of Zn2+ and Cu2+ from aqueous solution by sulphate and phosphate-modified Bentonite clay.

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 Cu(2+) and Zn(2+). 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 Zn(2+) 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 Cu(2+) and Zn(2+) were basically by chemisorption.

Fuzzy comprehensive assessment of metal contamination of water and sediments in Ondo Estuary, Nigeria

A more reliable methodology for evaluating metal contamination of coastal water and sediments using fuzzy comprehensive assessment (FCA) is presented by this study. Ten metals (As, Cd, Cu, Cr, Fe, Mn, Ni, Pb, V and Zn) were investigated in water and sediments from ten sampling sites and formulated into fuzzy matrix based on three contamination classifications of pristine, moderately enriched and extremely impacted categories using regulatory limits as criteria. The products of the matrices from membership function of the observed data and the weight matrices generate indices that classify the degree of metal impact on the sites. The results of the FCA show that the estuary is negatively impacted by metals in a range of 45.5–75.1% membership in the extremely impacted category with potential adverse effects on the ecosystem of the neighbouring Atlantic Ocean. The crude oil exploration activity at site 1 is the major source input of the metals beside Fe and Mn which are natural to the geological structure of the area while domestic waste discharges contribute notably to metal contamination in some sites.

Removal of Lead and Cadmium Ions from Aqueous Solution by Polyvinyl alcohol-modified Kaolinite Clay: A Novel Nano-clay Adsorbent

Kaolinite clay was modified with polyvinyl alcohol (PVA) to obtain a PVA–nano-clay adsorbent. X-Ray diffraction measurements of the adsorbent showed no observable change in the d-spacing of its crystal lattice. Scanning electron microscopy of the PVA-modified nano-clay adsorbent indicated the presence of irregular crystal structures. Infrared spectroscopy suggested that the PVA–nano-clay adsorbent basically possessed outer –OH functional groups. This adsorbent was found to have an adsorption capacity of 56.18 mg/g for Pb2+ ions and 41.67 mg/g for Cd2+ ions. The adsorption data obtained was well explained by the Diffuse Layer Model (DLM), which implies that the adsorption of both metal ions onto the modified adsorbent was via an inner-sphere surface complexation mechanism. The ΔH0 values for the adsorption of both metal ions onto the PVA–nano-clay were −12.48 kJ/mol for Pb2+ ions and −13.49 kJ/mol for Cd2+ ions, with both ions exhibiting negative adsorption entropies. Data-fitting indicated that both the PVA–nano-clay and the unmodified adsorbent possessed homogeneous and heterogeneous adsorption sites. Virtually complete desorption (ca. 99%) of both metal ions occurred from PVA–nano-clay within 3 min.

Competitive biosorption of Pb(II) and Cd(II) ions from aqueous solutions using chemically modified moss biomass (Barbula lambarenensis)

Treatment of biosorbents to add functional groups that increase toxic metal biosorption is an important way to improve its effective application. Hence, different portions of pristine Barbula lambarenensis (RBL) were treated separately with sodium tripolyphosphate (TPP) and ethylene glycol. The pristine and treated RBL biomasses were used to evaluate the simultaneous removal of Pb(II) and Cd(II) from aqueous solutions. Equilibrium, kinetics and adsorption isotherms were studied. Results revealed that biosorption of Pb(II) and Cd(II) metal ions were spontaneous and described by the pseudo-second-order kinetics. TPP-treated RBL showed higher biosorption capacity for Pb(II), while the ethylene glycol-treated adsorbent was more efficient for Cd(II) biosorption. The simultaneous presence of Pb(II) and Cd(II) in solution did not affect Pb(II) biosorption. However, Cd(II) biosorption dropped 44, 42 and 19% for the pristine, ethylene glycol and TPP-treated adsorbents, respectively, in the competitive adsorption. Both treatments enhanced Pb(II) and Cd(II) biosorption by RBL.

Distribution and interactions of pentachlorophenol in soils: The roles of soil iron oxides and organic matter.

Soil iron oxides (IOs) and organic matter (OM) play varying roles in pentachlorophenol (PCP) retention and mobility, but the extent and mechanism are still unknown. Therefore, in order to have a better understanding of the adsorption of PCP on soils, batch sorption studies were carried out on whole soils and soils selectively treated to remove IOs (IOR) and OM (OMR). The effects of pH, time, and temperature were investigated. Results showed that PCP sorption was temperature and pH dependent; sorption decreased as both temperature and pH increased. Sorption was partly surface adsorption and partly partitioning within voids of IOs components as revealed by the kinetics models. The surface adsorption was multi-layer in nature. Equilibria were faster in the IOR soils than the untreated and OMR soils. IOs played greater roles in PCP sorption than OM. Removal of soil components, especially the IOs, as experienced in soils plagued by soil erosion, may lead to increased risks of PCP pollution of environmental media especially the aquifer.

Comparison of two-stage sorption design models for the removal of lead ions by polyvinyl-modified Kaolinite clay.

Kaolinite clay obtained from Ubulu-Ukwu, Delta State in Nigeria was modified with polyvinyl-alcohol (PVA) reagent to obtained PVA-modified Kaolinite clay. Kinetic and equilibrium data were obtained for the batch adsorption of Pb(2+) onto PVA-modified Kaolinite clay. Time-dependent Langmuir and pseudo-second order kinetic models (TDLM and PSOM) were developed to predict the optimized minimum operating time for the adsorption of Pb(2+) onto PVA-modified Kaolinite clay in a two-stage batch adsorber system. Results obtained suggest that the two-stage batch adsorber process leads to improved contact time and increased percentage Pb(2+) removal. Data from both models (TDLM and PSOM) were compared using t-test and F-test and were found to be precise enough for use in the optimization of kinetic data for a two-stage adsorption of Pb(2+) ions from aqueous solution.

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...