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Generally, environmental pollution is a global problem and the treatments of wastewater have been an outstanding challenge these days. Increased inhabitants, metropolitanism and industrialization have in one way or the other contributed to the environmental hazards. The delimitation of the conventional treatment of wastewater has made researchers to explore novel and viable techniques that can mineralize pollutants without leftover in wastewater to have an environment free of pollutants. Nanotechnology is a promising technology that uses nano-sized materials with unique properties such as small size and large surface area to remove pollutants in aqueous environment. Nano-sized zinc oxide is of great importance as it has high photocatalytic ability, no secondary pollutant, non-toxic, biologically safe, cost-effective, synthesized effortlessly and stable under harsh environment. The utilization of zinc as starting materials for the synthesis of n-sized ZnO was studied extensively, and its availability makes it to be synthesized in various ways such as green synthesis, wet chemical method, precipitation, sol–gel method, co-precipitation, microwave and electrochemical synthesis. It is worthy of note that the mechanism of degradation of pollutants by nano-sized zinc oxide via photocatalysis, sonolysis, adsorption, coagulation and ozonation is vital in achieving complete mineralizing of pollutants in wastewater.

In this study, the adsorption of Ni(II) and Cu(II) ions from aqueous solutions by powdered Delonix regia pods and leaves was investigated using batch adsorption techniques. The effects of operating conditions such as pH, contact time, adsorbent dosage, metal ion concentration and the presence of sodium ions interfering with the sorption process were investigated. The results obtained showed that equilibrium sorption was attained within 30 min of interaction, and an increase in the initial concentration of the adsorbate, pH and adsorbent dosage led to an increase in the amount of Ni(II) and Cu(II) ions adsorbed. The adsorption process followed the pseudo-second-order kinetic model for all metal ions' sorption. The equilibrium data fitted well with both the Langmuir and Freundlich isotherms; the monolayer adsorption capacity (Q0 mg g−1) of the Delonix regia pods and leaves was 5.88 and 5.77 mg g−1 for Ni(II) ions respectively and 9.12 and 9.01 mg g−1 for Cu(II) ions respectively. The efficiency of the powdered pods and leaves of Delonix regia with respect to the removal of Ni(II) and Cu(II) ions was greater than 80 %, except for the sorption of Ni(II) ions onto the leaves. The desorption study revealed that the percentage of metal ions recovered from the pods was higher than that recovered from the leaves at various nitric acid concentrations. This study proves that Delonix regia biomass, an agricultural waste product (“agro-waste”), could be used to remove Ni(II) and Cu(II) ions from aqueous solution.

Pharmaceuticals (PhACs) are a class of emerging contaminants of global concern due to their ubiquitous nature, persistence and capability of affecting humans and aquatic lives negatively even at very low concentrations. Conventional wastewater treatment procedures are generally inadequate for removing these contaminants. Photocatalysis, an advance oxidation process (AOP), has been widely used in eliminating PhACs from wastewater. This is due to its low operational cost compared to other AOPs. However, the problem of complete mineralization of PhACs by photocatalysis remains a challenge. In this review, we discussed photocatalysis, biodegradation and mechanisms of action for the degradation of PhACs in wastewaters. The application of a combined photocatalytic biodegradation systems for the degradation of PhACs in wastewater was also presented. It is worthy of note that several operating parameters such as the biotic and abiotic factors are pivotal to an efficient photocatalytic and biodegradation treatment systems. Therefore, an integrated photocatalysis/biodegradation system is essential to achieving a complete mineralization of PhACs; other advantages of this treatment technique include low energy cost, effective degradation process, generation of non-toxic by-product and self-sustenance energy generation.

Iron nanoparticles (nano Fe) were extracted from coal fly ash (CFA) or ferric chloride (FeCl3) and used for acid mine drainage (AMD) remediation. Characterisation was achieved by X-ray diffraction (XRD), X-ray fluorescence, scanning electron microscopy-energy dispersive spectroscopy (SEM–EDX), high resolution transmission electron microscopy (HRTEM), and the Braunaer–Emmet–Teller (BET) surface area determination. The HRTEM indicated good dispersion of the characteristic bead-like structure of nano Fe. It was also observed that the nano Fe were mainly in the zero-valent oxidation state, as denoted by the characteristic peak at ≈ 44.7° in the XRD analysis; it was accompanied by the generally accepted oxide layer around the particles, which was confirmed by the appearance of a core–shell structure in the HRTEM micrographs. The BET surface areas of the nano Fe extracted from the CFA or FeCl3 were recorded to be 34.7 or 88.8 m2/g, respectively. The nano Fe lowered the concentration of most of the monitored contaminants, with the percentage removal ranging from 17 to 99%. The pH of the AMD after treatment with nano Fe obtained from CFA or FeCl3 increased to 5.74 or 6.01, respectively, from 3.49, the electrical conductivity decreased to 0.18 or 0.13 Ω/m, respectively from 0.57 Ω/m, while the total dissolved solids was decreased to 447 or 384 mg/L, respectively, from 1683 mg/L. The water quality of the treated AMD is suitable for Category 4 industrial use, per the Dept. of Water Affairs and Forestry’s limits.

The removal of Pb(II) ions from synthetic wastewater using Delonix regia pods and leaves as low-cost biosorbents was investigated. The elemental, morphological and phase characterization of Delonix regia pods and leaves were examined before and after biosorption. The adsorption process at various pH values, contact times, initial concentration of Pb(II) ions and adsorbent doses was studied with the aim of investigating the consequences of these parameters on the process of biosorption. The Langmuir adsorption isotherm provided the best fit for the experimental data of the pods while the Freundlich isotherm gave a better fit for the leaves of Delonix regia. The optimum adsorption capacity of 30.27 mg/g for the pods and 27.60 mg/g for the leaves was achieved when 0.5 g of the adsorbent was mixed with 20 mL of 1,000 mg/L Pb(II) ions solution for 30 min at 21 ± 2 °C and a stirring speed of 18 rpm. The data obtained from the time-dependent experiment of the biosorbents followed the pseudo-second-order kinetic model. This study showed that Delonix regia pods and leaves could be developed further as a low-cost sorbent that could be harnessed for removing Pb from industrial wastewater and thus limit water pollution from point sources.

The adsorption of alizarin red (AR) dye onto termite hill sample (THs) was investigated. Prior to the adsorption studies, the elemental, morphological, surface and structural properties of THs were examined by modern analytical methods. Instrumental analysis showed that the homogenous micro-structured THs are comprised of iron oxide, silica oxide, and alumina as major components. Experiments showed that the adsorption capacity of AR decreases with increasing pH and initial AR concentrations, and increases with increasing contact time, stirring speed and temperature. The equilibrium study obeyed the Langmuir adsorption model and the kinetics followed the pseudo-second-order model. About 95.0% AR reduction (1.425 mg/g) was achieved when 0.8 g of THs was mixed with 30 mL of 40 mg/L AR solution for 120 min at 400 rpm and a pH of 2. Thermodynamic study suggested that AR adsorption onto THs is spontaneous at higher temperatures of 323 K and above (ΔGo values are negative). However, ΔGo are positive at lower temperatures of 293–313 K, which implies that the adsorption process is not spontaneous at these temperatures. This study showed that THs could be used as alternative, low-cost, natural adsorbents for the removal of dyes from wastewater.

In this study, the use of ultra-violet (UV) light with or without iron oxide nanoparticles (IONPs) for the degradation of synthetic petroleum wastewater was investigated. The IONPs was synthesised by sodium borohydride reduction of ferric chloride solution and was characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FTIR), x-ray fluorescence spectrophotometry (XRF), and energy dispersive spectroscopy (EDS). The amount of degradation was evaluated by chemical oxygen demand (COD) determination. Experimental results show that the COD removal from synthetic petroleum wastewater by IONPs/UV system was more effective than they were independently. The combination of UV light at a wavelength of 254 nm, pH of 8, and 1.0 g of IONPs resulted in COD removal from 10.5% up to 95.5%. The photocatalytic degradation of synthetic petroleum wastewater is about 1.3–2.0 times faster in comparison to UV light only. The removal of COD from synthetic petroleum wastewater by UV light and IONPs follows the pseudo-first-order kinetic model with rate constant k ranging from 0.0133 min−1 to 0.0269 min−1. Consequently, this study has shown that the use of UV light in the presence of IONPs is favourable and effective for the removal of organic pollutants from petroleum refinery wastewater.

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.

In this study, the adsorption of amido black (AB) dye onto kaolin was investigated. The characterization of kaolin was carried out by powder x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). Adsorption studies showed that the adsorption of AB onto kaolin increased with increasing adsorbent dosage, contact time, pH and temperature but decreased with increasing dye concentration. Equilibrium data fitted perfectly into the Langmuir and Freundlich equilibrium models, moreover, the kinetic data followed the pseudo-second order model. The adsorption process is endothermic and approximately 60.75% AB reduction was achieved when 0.75 g of kaolin was mixed with 20 mL of 40 mg/L AB for 60 min at 200 rpm. Therefore, this study shows that kaolin can be harnessed for the treatment of textile wastewater.

In this study, zinc oxide nanoparticles (nano-ZnO) was effectively synthesised by precipitation method to catalyse the ultrasound degradation of amoxicillin aquaculture effluent. The nanoparticles at different calcination temperatures were characterised by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, x-ray diffraction, and Brunauer, Emmett and Teller (BET) surface area determination. Characterisation results indicated that Zn existed as different compounds at different temperature, besides, pure zincite (ZnO) was obtained at 500 °C having a BET surface area of 8.39 m2/g. The degradation experiments indicated that the ultrasound/H2O2 system with nano-ZnO was more effective for amoxicillin degradation than they were independently. The ultrasound/H2O2 system with nano-ZnO could be described by the Langmuir-Hinshelwood kinetic model. The addition of H2O2 and nano-ZnO to the ultrasound reactor enhanced the degradation of amoxicillin from 46.87% up to 98.9%. The recyclability and stability of nano-ZnO also showed that the catalytic activity of nano-ZnO during ultrasound degradation of amoxicillin was not lost up to five cycles. Thus, the application of ultrasound in the presence of H2O2 and nano-ZnO is favorable and effective for the remediation of aquaculture effluent.

Over the years, significant effort has been devoted to the applications of graphitic carbon nitride (g-C3N4) nanomaterials due to their outstanding properties. Which include thermal, mechanical, and electrical properties, non-toxicity, low-cost, metal-free nature, large surface area, optical, ease of preparation, environmental friendliness, biocompatibility and chemical inertness. In this article, the various applications and prospects of g-C3N4 materials in biomedicine, sensors, energy conversion and storage, hydrogen production, mixed matrix membranes for water treatment, and photocatalytic degradation of aqueous organic pollutants has been critically reviewed. Moreover, key aspects of photocatalytic CO2 reduction and the suitability of g-C3N4 as photocatalyst have been covered. The review also discusses theoretical aspects, attributes, current trends/challenges and future considerations associated with the energy and environmental application of g-C3N4 nanostructures. It is believed that this review will provide a current comprehensive knowledge of the applications of g-C3N4 to readers and researchers to identify research gaps and could inspire researchers to synthesize novel g-C3N4-based materials for use in potential diverse fields.

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.

The biosorption characteristics of Pb (II) ions from aqueous solution using black walnut (Juglans nigra) seed husk (WSH) biomass were investigated using batch adsorption techniques. The effects of pH, contact time, initial Pb (II) ion concentration, and temperature were studied. The Langmuir, Freundlich and Temkin isotherms were used to analyze the equilibrium data. It was found that the adsorption of Pb (II) ions onto WSH was best described by the Freundlich adsorption model. Biosorption kinetics data were tested using the pseudo-first order and pseudo-second order models, and it was observed that the kinetics data fitted the pseudo-second order model. Thermodynamic parameters such as standard Gibbs free energy change (ΔG0), standard enthalpy change (ΔH0) and standard entropy change (ΔS0) were evaluated. The result showed that biosorption of Pb (II) ions onto WSH was spontaneous and endothermic in nature. The FTIR study showed that the following functional groups: O-H, C = O, C-O, C-H and N-H were involved in binding Pb (II) ions to the biomass.

Organic pollutants in water and wastewater have been causing serious environmental problems. The arbitrary discharge of wastewater by industries, and handling, use, and disposal constitute a means by which phenols, flame retardants (FRs), phthalates (PAEs) and other toxic organic pollutants enter the ecosystem. Moreover, these organic pollutants are not completely removed during treatment processes and might be degraded into highly toxic derivatives, which has led to their occurrence in the environment. Phenols, FRs and PAEs are thus highly toxic, carcinogenic and mutagenic, and are capable of disrupting the endocrine system. Therefore, investigation to understand the sources, pathways, behavior, toxicity and exposure to phenols, FRs and PAEs in the environment is necessary. Formation of different by-products makes it difficult to compare the efficacy of the treatment processes, most especially when other organic matters are present. Hence, high levels of phenols, FRs and PAEs removal could be attained with in-line combined treatment processes.

Bed sediment samples of the two headwaters of a tropical reservoir in Southwestern Nigeria were analysed for some metal concentrations using ICP-OES for a period of one year. Sediment samples were collected bi-monthly from both the lower and upper reaches of the streams from May 2013 to March 2014. Sediment samples were microwave-digested and analysed using ICP-OES. Concentrations of metals were higher in the lower reach than in the upper reach, and wet season concentrations were higher than in the dry season with the exception of Fe and Mn. The annual mean metal concentrations were as follows: Fe (121.72 ± 6.82 µg/g); Mn (9.34 ± 2.57 µg/g); Na (6.20 ± 2.29 µg/g); K (0.65 ± 0.57 µg/g); Mg (8.07 ± 1.36 µg/g); Ca (13.92 ± 2.85 µg/g); Ba (0.17 ± 0.17 µg/g); Al (106.54 ± 5.55 µg/g); and Se (0.6 ± 0.19 µg/g). These values were lower in comparison with the baseline concentrations of elements on the earth’s crust. Contamination assessment of all the metals investigated in this study showed that metals in...

Native cellulose (NC) was extracted from agricultural waste (flamboyant fruit pods) using acidified sodium sulphite treatment followed by mercerization with sodium hydroxide. Carboxyl methyl cellulose (CMC) and cellulose acetate (CA) derivatives were obtained via etherification and acetylation of NC respectively under acidic conditions. Chemical composition, structural crystallinity, morphology, thermal studies, degree of substitution and acetylation of modified cellulose were reported. Wide angle X-ray diffractometry showed remarkable reduction in structural crystallinity and increased amorphous character upon modificationof NC.Scanning Electron Microscopy (SEM) displayed irregular spherical morphology and rough spongy-like mass for native and modified cellulose respectively confirming the surface disruption upon acetylation and carboxylmethylation. Proximate analysis revealed a reduction in the ash and fat contents of modified cellulose. Thermal analysis showed improved stability upon chemical modification of the NC. CMC significantly enhanced the stability of vegetable oil-water emulsion and ensured successful encapsulation of vitamin A in oil phase.

A laboratory study was performed to study the effects of various operating factors, viz. adsorbent dose, contact time, solution pH, stirring speed, initial concentration and temperature on the adsorption of triphenyltin chloride (TPT) onto coal fly ash supported nZnO (CFAZ). The adsorption capacity increases with increase in the adsorbent amount, contact time, pH, stirring speed and initial TPT concentration, and decrease with increase in the solution temperature. The adsorption data have been analyzed by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) adsorption models to determine the mechanistic parameters associated with the adsorption process while the kinetic data were analyzed by pseudo first-order, pseudo second-order, Elovich, fractional power and intraparticle diffusivity kinetic models. The thermodynamic parameters of the process were also determined. The results of this study show that 0.5 g of CFAZ was able to remove up to 99.60% of TPT from contaminated natural seawater at 60 min contact time, stirring speed of 200 rpm and at a pH of 8. It was also found that the equilibrium and kinetic data fitted better to Freundlich and pseudo second-order models, respectively. It can therefore be concluded that CFAZ can be effectively used for shipyard process wastewater treatment

In this study, we attempted to verify the hypothesis that total metals bound to dust of different particle sizes may reflect pollution levels, but cannot predict its bioavailability and risks in human health assessments. Dust samples were collected using active sampling method; during the dry season months of November, 2014 to March, 2015 at different locations in Akure (7˚10ʹN and 5˚15ʹE). The samples were sorted into different particle sizes (< 10µm, 10 – 50 µm, >50µm), analyzed for some physicochemical properties and assessed for metals bioavailability using two-step physiological extraction method. The amount of metals (Cd, Cu, Cr, Ni, Pb, Zn and Mn) released in each particle sizes were determined using Perkin-Elmer 6000 Inductively Coupled Plasma - Atomic Emission Spectrometry (ICP-AES) analysis. The results showed that bioavailability of some metals (Cd, Ni, Pb, and Zn) decreases with increasing particle sizes, however, the reverse trend was observed for Mn, Cu and Fe concentrations. This may be attributed to some combination of physicochemical characteristics of the dust and metal speciation. Hence, it was concluded that metal bioaccessibility in dust can best be described by the knowledge of physicochemical characteristics. The exposure dose of the metals showed that cancer risks due to inhalation were very high when compared to other exposure routes (ingestion and dermal contact). The calculated non-cancer (HQ) and cancer risk (HI) for humans in the area showed values higher than unity, indicating possibility of the metals’ body burden.

In this study, the use of acid mine drainage as alternative source of ferric ion for the synthesis of iron nanoparticles was investigated. The physical and chemical characteristics of acid mine drainage from Navigation coal mine and the West Rand mine, South Africa were conducted. The synthesised iron nanoparticles were compared with iron nanoparticles prepared from commercial reagents by X-ray diffraction, X-ray fluorescence, scanning electron microscopy, high resolution transmission electron microscopy and Brunauer–Emmett–Teller surface area determination. The iron nanoparticles were utilised for the treatment of acid mine drainage. Experimental results showed that the characteristics of acid mine drainage samples differ from site to site due to the differences in their geological composition, chemical deposition, rate of oxidation, and availability of pyrite ores. The Toeseep acid mine drainage feedstock from Navigation coal mine was found to contain the highest concentration of iron (4219.14 mg L−1) thus; it was regarded to be a suitable source of iron, sulphate (21,317.79 mg L−1) was the predominant anion. The synthesised iron nanoparticles were crystalline and spherical in shape, with average particle size of 31.8 nm or 28.05 nm and Brunauer–Emmett–Teller surface area of 88 ± 3.16 m2 g−1 or 91 ± 3.08 m2 g−1 for the iron nanoparticles synthesised from acid mine drainage or ferric chloride, respectively. The optimisation of the iron nanoparticles dosage and contact time for the treatment of Navigation Toeseep acid mine drainage was determined to be 0.1 g and 60 min, respectively. The toxic elements in the raw acid mine drainage were removed with over 75% efficiency.

Pollution caused by agrochemicals and personal care products (PCPs) remains a severe problem worldwide. Runoff of agrochemicals from farms leads to contamination of the surface water and groundwater while PCPs are discharged through laundering, washing and bathing. PCPs enter the municipal wastewater treatment plants and are incompletely removed during wastewater treatment. To reduce or eliminate the negative impact of these pollutants to human beings, animals, organisms and the environment, water should be well treated and wastewater should be treated to zero release before discharge into the environment. In this study, the occurrence, toxic effects, analytical determination and treatment processes of agrochemicals and PCPs in water and wastewater will be presented. This review will serve as valuable literature for researchers, policy makers, and environmental pollution consultants. Moreover, it will open the door to significant discussion on agrochemicals and PCPs.

Hydrometallurgy is the most suitable extractive technique for the extraction and purification of manganese as compared to all other techniques including biometallurgy and pyrometallurgical processes. In the hydrometallurgical processing of manganese from its ore, the leach liquors often contain divalent ions such as iron, manganese, copper, nickel, cobalt and zinc along with other impurities which make manganese very difficult to separate. The processes employed for solution concentration and purification in the hydrometallurgical processing of manganese include precipitation, cementation, solvent extraction and ion exchange. Solvent extraction also proves more efficient and it plays vital roles in the purification and separation of the manganese as compared to all other techniques. A detailed review of the various steps involved in the hydrometal-lurgical manganese processing, concentration and purification processes and newer processes of extraction of manganese from ores and waste materials were discussed.

Activated carbon, silica, and composite material of silica and activated carbon were used as adsorbents to remove tributyltin (TBT) from artificial seawater, and the adsorption efficiencies for the precursors and the composite were compared. The composite presented higher TBT adsorption efficiency than the precursors. The adsorption of TBT onto these materials as a function of adsorbent amount, contact time, pH, stirring speed, initial adsorbate concentration, and temperature was investigated. Maximum TBT adsorption was recorded within the pH range of normal saline water (pH 8). The adsorption kinetics of TBT onto the adsorbents followed a pseudo-second-order kinetic model and the equilibrium adsorption data of TBT onto the precursors and composite were well represented by the Freundlich models. The calculated thermodynamic parameters indicated that TBT adsorption onto the precursor and the composite was spontaneous and endothermic. Optimal conditions for the adsorption of TBT from artificial seaw...

The removal of triphenyltin chloride (TPT) from contaminated artificial seawater by adsorption was investigated. The adsorbents used were nFe3O4/fly ash composite, nFe3O4, and fly ash. This study revealed that the sorption of TPT onto the adsorbents increase with the adsorbent dose, pH, stirring speed, and contact time, and decreased gradually with increase in the solution temperature. The equilibrium and kinetic data were analyzed by the Freundlich isotherm and pseudo second-order kinetic model, respectively. Experimental results therefore showed that 95.37, 96.44, and 98.40% of TPT were removed by the nFe3O4, fly ash, and nFe3O4/fly ash composite, respectively when the maximum conditions for the adsorption of TPT from artificial seawater were applied to TPT – contaminated shipyard wastewater.

Background The removal of tributyltin (TBT) from shipyard process wastewater using fly ash, activated carbon and fly ash/activated carbon composite was investigated. Results Adsorption experiments performed on TBT-contaminated artificial process wastewater revealed that the adsorption capacity of TBT increases with increase in the adsorbent amount, contact time, pH, stirring speed and initial TBT concentration. The adsorption isotherms and the kinetic data were well described by the Freundlich and pseudo-second-order kinetic model, respectively. The negative values of the Gibbs energy change (ΔGo) indicated the spontaneous nature of the adsorption and the positive values of the enthalpy change (ΔHo) showed that the adsorption process is endothermic. Optimal conditions for the adsorption of TBT from contaminated artificial process wastewater were applied to TBT removal from natural shipyard process wastewater and the results showed that 94.2%, 99.2% and 99.8% TBT were removed by the fly ash, activated carbon and fly ash/activated carbon composite, respectively. Conclusion This study showed that the precursors as well as the composite could be employed as efficient adsorbents for the removal of TBT from contaminated shipyard process wastewater with the composite material exhibiting the highest adsorption efficiency. © 2013 Society of Chemical Industry

Chalcopyrite ores are usually processed by means of hydrometallurgical or pyrometallurgical processes, but due to environmental aspects and the possibility of increased exploitation of mixed and lower grade ores and relatively small isolated deposits, there has been a worldwide upsurge of interest in the hydrometallurgical processes of this ore as compared to pyrometallurgy. The different concentrates obtained through differential flotation in pyrometallurgy are usually of poor quality with low metal recovery. This further makes pyrometallurgical processing of chalcopyrite very difficult and costly and rendered them difficult to commercialize. As a result, the metal value is preferably extracted directly from low grade ores through hydrometallurgical process. A detailed review of chalcopyrite deposits, production and consumption, mining, ore processing, steps involved in the pyrometallurgical and hydrometallurgical processing of copper as well as the dissolution kinetics and microbial studies of chalcopyrite ore were discussed.

This paper presents the kinetics of dissolution of a Nigerian colu mb ite mineral ore sample in hydrochloric acid med ia. The effects of acid concentration, process temperature, stirring rate and particle size on the dissolution rate were examined. Experimental results showed that the columbite dissolution increases with increasing acid concentration, temperature, stirring speed and decreases with particle size. W ith 4.0 M HCl solution, about 15.37% of colu mbite was dissolved within 120 minutes using < 0.15 mm particle size at a temperature of 80℃ and a stirring speed of 360 rp m. The result of the study indicated that the leaching data fitted a diffusion model. Values of 0.5, 22.40 kJmo l -1 and 1.51 X 10 -5 min -1 were calculated as reaction order, activation energy and Arrhenius constant, respectively for the dissolution process.

Organotin compounds are chemical compounds based on tin with hydrocarbon substituent used in manufacturing industries, especially the antifouling paint industries. These paints are used to prevent the growth of fouling organisms on marine structures and vessels. They are directed at organisms that settle on solid surfaces after a period of mobility in the sea. Organotin antifouling paints are thus exceptional toxic and they interfere with biological processes in a diverse range of species and as a result been banned in many countries around the world. However, these paints are still applied to large shipping vessels while some third world countries are still utilizing them on smaller vessels. There is therefore a need to prevent a significant part of the introduction of antifouling compounds into the marine ecosystem by treatment of shipyard and antifouling paint industrial wastewaters to about 99% reduction on its concentration before discharge into the marine ecosystem.

The preparation and physicochemical characterization of activated carbon, nano metal oxides, and activated carbon – nFe3O4, activated carbon – nSiO2 and activated carbon – nZnO hybrid materials has been undertaken. The materials have been characterized by scanning and transmission electron microscopy, x-ray diffraction, CNH analysis and Fourier transform infrared spectroscopy. Surface area and porosity, ash content, pH, and point of zero charge were also measured. The results showed that the surfaces of activated carbon, nSiO2, activated carbon – nFe3O4, activated carbon – nSiO2 and activated carbon – nZnO are suitable for the sorption of cationic complexes while the surfaces of nFe3O4 and nZnO are favourable to the sorption of anionic complexes of heavy metals. Results also showed that the composition of the activated carbon and nano metal oxides increased the surface and micropore areas of nano metal oxides due to the large number of micropores and crevices on the surface of the hybrid materials.

Niobium and tantalum are chemically similar and are associated with each other in nature which makes it very difficult to separate. For many years, the separation of tantalum from niobium involved the fractional crystallization of potassium heptafluorotantalate away from potassium oxypentafluoroniobate monohydrate, this method has been supplanted by solvent extraction from fluoride-containing solutions by the use of solvent extractants such as Octanol, bis(2-ethylhexyl)phosphoric acid (DEHPA), Alamine 336, methyl isobutyl ketone (MIBK), tri-nbutyl phosphate (TBP) or cyclohexanone. A detailed review of the various processes involved in the breakdown treatment of niobium and tantalum primary sources, extraction and separation and newer processes of extraction as well as the various technique involved were discussed. Keyword: Niobium, Tantalum, Columbite, Tantalite, Solvent extractant and Solvent extraction.

Studies on the kinetics of dissolution of a Nigerian lateritic soil in acids media including hydrochloric, nitric and sulphuric acids have been undertaken. The elemental and mineralogical characterization, loss of mass on ignition, moisture content and pH of the material suspension in water were determined. The effects of acid concentration, process temperature, stirring rate and particle size on the dissolution rate were investigated. Experimental results indicated that laterite dissolution was greatly influenced by hydrogen ion concentration and the leaching data fitted a diffusion model. The linear dependence of the rate constant k on 1/r o 2 supported the proposed kinetic model. Values of 60.23 kJmol -1 , 64.31 kJmol -1 and 67.53 kJmol -1 were obtained for the activation energies of laterite dissolution in hydrochloric, nitric and sulphuric acids respectively; and the order of reaction was approximately one with respect to each of the three acids.

The decolorization of congo red (CR) in aqueous solution was investigated in a batch mode using termite mound as adsorbent. Elemental analysis and identification of the mineral composition/phases in the termite mound sample was carried out by means of X-ray fluorescence and X-ray diffraction. The optimal percentage removal and equilibrium adsorption capacity of CR by the termite mound achieved was found to be 95.68% and 2.30 mg/g, respectively, when 0.5 g of termite mound was added to 30 mL of 40 mg/L CR for 60 min at 400 rpm. The decolorization of CR increased with increase in the termite mound dosage, contact time, stirring speed, pH and temperature; however, the adsorption capacity decreased with increase in the initial CR concentration. The adsorption process showed that CR obeyed the Freundlich adsorption model with 0.9355 coefficient of regression, denoting multilayer formation onto the termite mound. The adsorption kinetics followed the pseudo-second order model with a coefficient of regression value of 0.9966, showing that chemisorption is the main rate limiting step. ΔG is negative, an indication that the adsorption of CR onto termite mound is spontaneous. Approximately 86.6% chemical oxygen demand reduction was achieved with real textile wastewater. This research has shown harness of termite mound for the treatment of textile wastewater before discharged into the environment.

In this study, bamboo impregnated with nanoscale zero-valent iron (nZVI) and nanoscale manganese (nMn) were prepared by the aqueous phase borohydride reduction method and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and PIXE analysis. The synthesized nMn-bamboo and nZVI-bamboo composites were subsequently applied to the sorption of methylene blue (MB) dye from aqueous solution. The adsorption of MB dye was investigated under various experimental conditions such as pH, contact time, initial concentration of MB dye and adsorbent dosage. The results showed that the synthesized nZVI-bamboo composite was more effective than nMn-bamboo composite in terms of higher MB dye adsorption capacity of 322.5 mg/g compared to 263.5 mg/g of nMn-bamboo composite. At a concentration of 140 mg/L MB dye, 0.02 g of nZVI-bamboo and nMn-bamboo composites resulted in 79.6% and 78.3% removal, respectively, at 165 rpm, contact time of 120 min and at a solution pH of 7.6. The equilibrium data was best represented by Freundlich isotherm model and the pseudo-second order kinetic model better explained the kinetic data for both nZVI-bamboo and nMn-bamboo composites.

The remediation of tributyltin (TBT) by adsorption onto nFe3O4, activated carbon and nFe3O4/activated carbon composite material as a function of adsorbent dose, contact time, pH, stirring speed, initial TBT concentration and temperature was studied. The effect of temperature on kinetics and equilibrium of TBT sorption on the precursors and the composite was thoroughly examined. The adsorption kinetics is well fitted using a pseudo-second-order kinetic model, and the adsorption isotherm data of nFe3O4, activated carbon could be described by the Freundlich isotherm model whereas nFe3O4/activated carbon composite could be described by the Freundlich and Dubinin–Radushkevich isotherm models. Thermodynamic parameters (i.e. change in the free energy (∆G°), the enthalpy (∆H°) and the entropy (∆S°)) were also evaluated. The overall adsorption process was endothermic and spontaneous in nature. The results obtained also showed that 99.9, 99.7 and 80.1 % TBT were removed from contaminated natural seawater by nFe3O4/activated carbon composite, activated carbon and nFe3O4, respectively.

The removal of triphenyltin chloride from contaminated simulated seawater with adsorption method was discussed. The adsorbents used are fly ash, nSiO2, and nSiO2/fly ash composite. The results showed that the adsorption of the adsorbents increases with increase in the adsorbent dose, contact time, pH, stirring speed, initial TPT concentration, and decreased with increase in temperature. The adsorption fitted well with the Freundlich isotherm, showing that the adsorbent and TPT combined with function groups and the adsorption kinetics followed the pseudo-second-order kinetic model. The thermodynamic parameters were also evaluated. Optimal conditions for the adsorption of TPT from simulated seawater were applied to TPT removal from natural seawater. A higher removal efficiency of TPT (>99 %) was obtained for the nSiO2/fly ash composite but not for fly ash and nSiO2.

The physicochemical properties, nature, and morphology of composite materials involving activated carbon, fly ash, nFe3O4, nSiO2, and nZnO were investigated and compared. Nature and morphology characterizations were carried out by means of scanning electron and transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Other physicochemical characterizations undertaken were CNH analysis, ash content, pH, point of zero charge, and surface area and porosity determination by BET. Experimental results obtained revealed that activated carbon, nSiO2, activated carbon-fly ash, activated carbon-fly ash-nFe3O4, activated carbon-fly ash-nSiO2, and activated carbon-fly ash-nZnO composite materials exhibited net negative charge on their surfaces while fly ash, nFe3O4, and nZnO possessed net positive charge on their surfaces. Relatively higher removal efficiency (>99%) of TBT was obtained for all the composite materials compared to their respective precursors except for activated carbon. These composite materials therefore offer great potential for the remediation of TBT in wastewaters.

The removal of tributyltin (TBT) from artificial seawater using n ZnO, activated carbon and n ZnO/activated carbon composite was systematically studied. The equilibrium and kinetics of adsorption were investigated in a batch adsorption system. Equilibrium adsorption data were analyzed using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherm models. Pseudo first- and second-order, Elovich, fractional power and intraparticle diffusion models were applied to test the kinetic data. Thermodynamic parameters such as Δ G °, Δ S ° and Δ H ° were also calculated to understand the mechanisms of adsorption. Optimal conditions for the adsorption of TBT from artificial seawater were then applied to TBT removal from natural seawater. A higher removal efficiency of TBT (>99%) was obtained for the n ZnO/activated carbon composite material and for activated carbon but not for n ZnO.

Mobile phones work by transmitting and receiving radio frequency microwave radiation. The radio frequency (RF) emitted by mobile phones is stronger than FM radio signal which are known to cause cancer. Though research and evidence available on the risk of cancer by mobile phones does not provide a clear and direct support that mobile phones cause cancers. Evidence does not also support an association between exposure to radio frequency and microwave radiation from mobile phones and direct effects on health. It is however clear that lack of available evidence of cancer as regards the use of mobile phone should not be interpreted as proof of absence of cancer risk, so that excessive use of mobile phones should be taken very seriously and with caution to prevent cancer.

A detailed physicochemical characterization of columbite and tantalite samples from different locations in Nigeria has been undertaken. Parameters such as moisture content, loss of mass on ignition, pH, and the specific gravity of columbite and tantalite samples from different locations were determined and compared. The results showed that the moisture content of columbite samples obtained from Kwara and Plateau States are 1.0 and 0.53 %, respectively, while the percentage of moisture content of tantalite samples obtained from Kwara, Kogi, Kaduna, and Nasarawa States are 0.37, 0.30, 0.67 and 1.00 %, respectively. The percentage loss of mass on ignition of columbite samples obtained from Kwara and Plateau States and tantalite samples from Kwara, Kogi, Kaduna, and Nasarawa States are 6.1, 3.6, 7.7, 2.4, 4.4 and 4.3 %, respectively. Values of 2.40, 3.76, 3.65, 3.37, 2.07 and 1.96 were obtained as the specific gravities of columbite samples obtained from Kwara and Plateau States and tantalite samples from Kwara, Kogi, Kaduna, and Nasarawa States, respectively, and finally, the mean pH for each of columbite and tantalite samples was approximately 7.6.

In this study, fly ash was obtained from Matla power station and the physicochemical properties investigated. The fly ash was characterized by x-ray fluorescence, x-ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectrometry. Surface area, particle size, ash and carbon contents, pH, and point of zero charge were also measured. The results showed that the fly ash is alkaline and consists mainly of mullite (Al6Si2O13) and quartz (SiO2). Highly toxic metals As, Sb, Cd, Cr, and Pb as well as metals that are essential to health in trace amounts were also present. The storage and disposal of coal fly ash can thus lead to the release of leached metals into soils, surface and ground waters, find way into the ecological systems and then cause harmful effect to man and its environments.

Nitrification is an important biological process in nitrogen cycling and has a significant effect on effluent quality in wastewater treatment. Nitrification occurs in two steps by two types of chemoautotrophic bacteria, the ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). The ammonia oxidizing bacteria is responsible for the oxidation of ammonia with oxygen into nitrite and is often the rate-limiting step in nitrification in wastewater treatment plants. Hence, a better understanding of the ecology, microbiology and chemistry of ammonia oxidizing bacteria in biological wastewater treatment systems is necessary in order to enhance treatment performance and control. A detailed review of various biological wastewater treatment processes, ammonia oxidizing bacteria and archaea; economic importance, problems, various molecular techniques for the investigation of the diversity and community structure, as well as the isolation of ammonia oxidizing bacteria were discussed.

The use of triphenyltin chloride (TPT), a persistent organic pollutant, as a biocide has led to serious contamination of the marine environment. The potential of nano zinc oxide (nZnO) for the removal of TPT from contaminated dockyard wastewater was investigated. The adsorption of TPT onto nZnO has been found to depend on the adsorbent dose, contact time, pH, stirring speed, and temperature. Equilibrium data fitted well with the Freundlich model and the experiments showed that 97.0% TPT removal was achieved by treating 0.643 mg·l-1 TPT contaminated dockyard wastewater with 0.5 g nZnO at optimal conditions. The kinetic data for the adsorption process obeyed a pseudo second-order kinetic model, suggesting that the adsorption process is chemisorption. The nZnO investigated in this study showed good potential for the removal of TPT from contaminated dockyard wastewater systems. Keywords : persistent organic pollutants, triphenyltin chloride, nano zinc oxide, adsorption, dockyard wastewater