BTEX compounds in water – future trends and directions for water treatment

Abstract: BTEX (benzene, toluene, ethylbenzene, and xylene) compounds are common water resource and potable water pollutants that are often left undetected and untreated by municipal treatment systems in spite of the negative repercussions associated with their ingestion. The US EPA has classified these pollutants as priority pollutant, yet they are persistently present in a variety of water resources. In this review paper, we highlight the sources and reported concentrations of BTEX compounds in water and explore historical remediation techniques that have been applied such as bioremediation and natural attenuation. We also highlight emerging possibilities and future directions for remediation techniques, such as nanotechnology-based materials and novel green materials (tannins) that can be applied to ensure removal of these compounds in water

Review: BTEX compounds in water – future trends and directions for water treatment

BTEX (benzene, toluene, ethylbenzene, and xylene) compounds are common water  resource and potable water pollutants that are often left undetected and untreated by  municipal treatment systems in spite of the negative repercussions associated with their ingestion. The US EPA has classified these pollutants as priority pollutant, yet  they are persistently present in a variety of water resources. In this review paper, we highlight the sources and reported concentrations of BTEX compounds in water and explore historical remediation techniques that have been applied such as  bioremediation and natural attenuation. We also highlight emerging possibilities and future directions for remediation techniques, such as nanotechnology-based materials and novel green materials (tannins) that can be applied to ensure removal of these  compounds in water. Keywords: adsorbents, biosorbents, BTEX, remediation, nanotechnology, water qualit

Assessment Of The Effects Of Guinea Corn Husk Ash On Lime-Stabilized Lateritic Soil

This study assesses the effects of Guinea Corn Husk Ash (GCHA) on lime stabilized lateritic soil. Preliminary tests were carried out on natural soil sample, for the purposes of identification and classification. The soil sample was classified as A-7-5. Hydrated lime was added to the soil sample at varying proportions of 2, 4, 6, 8 and 10% by weight of soil, thereafter, each of the mixes was subjected to atterberg limits tests to get the optimal amount of lime required, which was 10% lime because it was at this amount of lime that the least value of plasticity index was obtained. The guinea corn husk ash was later added to the lime-treated lateritic soil at proportions of 2, 4, 6, 8 and 10%. Each of the mixes was subjected to compaction, California bearing ratio (CBR), atterberg limits and unconfined compressive strength (UCS) tests. Results from these tests showed improvement in soil properties, also, the values of the CBR and UCS increased considerably. It can be concluded that the GCHA performs satisfactorily as a cheap complement for lime in stabilizing lateritic soil.

Biohydrogen production as a potential energy fuel in South Africa

Biohydrogen production has captured increasing global attention due to it social, economic and environmental benefits. Over the past few years, energy demands have been growing significantly in South Africa due to rapid economic and population growth. The South African parastatal power supplier i.e. Electricity Supply Commission (ESKOM) has been unable to meet the country’s escalating energy needs. As a result, there have been widespread and persistent power cuts throughout the country. This prompts an urgent need for exploration and implementation of clean and sustainable energy fuels like biohydrogen production in order to address this crisis. Therefore, this paper discusses the current global energy challenges in relation to South Africa’s problems. It then examines the feasibility of using biohydrogen production as a potential energy fuel in South Africa. Finally, it reviews the hydrogen-infrastructure development plans in the country

Development of Silica Sodalite With Enhanced Porosity via Topotactic Synthesis for Pre Combustion Co2 Capture

Topotactic conversion of layered silicates is reported to yield sodalite with enhanced frameworks, chemical compositions and predictable outcomes. Traditional hydrothermal synthesis results in sodalite with occluded matter preventing the effective use of sodalite cages for adsorption and separation applications. However, the reproducibility of high quality silica sodalite depends on obtaining optimized synthesis conditions and investigating the effect these conditions is essential. A 23 factorial design was employed to investigate the effect of process variables (acid strength, acid treatment time and calcination temperature) on the quality of silica sodalite produced via topotactic conversion in this study. XRD, SEM and Nitrogen physisorption at 77K were used for physio-chemical characterization of the sodalite samples. The produced sodalite crystals were used in membrane synthesis, and the membrane was tested for CO2/H2/N2 separation. Sodalite of desirable crystallinity and plate-like morphology was produced with surface area and porosity of 79.44m2/g and 0.081cm3/g, respectively. An incomplete transformation of sodalite at low acid concentration and treatment time was experienced. A significant improvement on surface area and pore volume was reported on all samples as compared to that of the hydroxy sodalite. Analysis of the regression model obtained from the experimental data indicates acid treatment time as an insignificant variable. The preliminary investigation of the application for membrane synthesis indicates enhanced porosity of the HSOD improved the membrane H2 permeance by 178%.publishedVersio

Development of Silica Sodalite With Enhanced Porosity via Topotactic Synthesis for Pre Combustion Co2 Capture

Topotactic conversion of layered silicates is reported to yield sodalite with enhanced frameworks, chemical compositions and predictable outcomes. Traditional hydrothermal synthesis results in sodalite with occluded matter preventing the effective use of sodalite cages for adsorption and separation applications. However, the reproducibility of high quality silica sodalite depends on obtaining optimized synthesis conditions and investigating the effect these conditions is essential. A 23 factorial design was employed to investigate the effect of process variables (acid strength, acid treatment time and calcination temperature) on the quality of silica sodalite produced via topotactic conversion in this study. XRD, SEM and Nitrogen physisorption at 77K were used for physio-chemical characterization of the sodalite samples. The produced sodalite crystals were used in membrane synthesis, and the membrane was tested for CO2/H2/N2 separation. Sodalite of desirable crystallinity and plate-like morphology was produced with surface area and porosity of 79.44m2/g and 0.081cm3/g, respectively. An incomplete transformation of sodalite at low acid concentration and treatment time was experienced. A significant improvement on surface area and pore volume was reported on all samples as compared to that of the hydroxy sodalite. Analysis of the regression model obtained from the experimental data indicates acid treatment time as an insignificant variable. The preliminary investigation of the application for membrane synthesis indicates enhanced porosity of the HSOD improved the membrane H2 permeance by 178%

Synthesis and Characterization of Nanocomposite Hydroxy-Sodalite/Ceramic Membrane via Pore-Plugging Hydrothermal Synthesis Technique

In this article, synthesis and characterization of nanocomposite hydroxy sodalite (H-SOD)/α-alumina membrane via the so-called “pore-plugging†hydrothermal synthesis (PPH) protocol is reported for the first time. In nanocomposite architecture membranes, zeolite crystals are embedded within the pores of the supports instead of forming thin-film layers of the zeolite crystals on the surface of the supports. The as-prepared membranes were characterized with SEM and FTIR for morphology and purity of the H-SOD crystals. Compared to the conventional in-situ direct hydrothermal synthesis, membranes obtained from PPH possess higher mechanical and thermal stability. In addition, defect control with nanocomposite architecture membrane is possible because the zeolite crystals are embedded within the support pores of the membrane, thereby limiting the maximum defect size to the pore sizes of support. The nanocomposite architecture nature of the membranes safeguards the membrane from shocks or abrasion that could promote defects/inter-crystalline pores formation. These advantages could be helpful in the scale-up process of the preparation procedure of membranes at the commercial level with less-demanding conditions

Adsorption of BTEX compounds from water using green-synthesized iron nanoparticles

Abstract: Please refer to full text to view abstract

A review of columnar cell lesions of the breast in a Lagos Tertiary Health Institution: A ten-year retrospective study

This study was to estimate the frequency of occurrence of columnar cell lesions (CCLs) in Nigerian women using Fibrocystic changes (FCC) of the breast as a surrogate lesion as well as to determine the variants of CCLs found using the standard histologic criteria.The materials for this study consisted of all consecutive breast biopsy blocks and corresponding archival slides with a previous diagnosis of FCC within a 10-year period at the department. All cases were reviewed and reclassified. The data obtained was analysed manually using simple statistical methods such as chart and tables. In this study, thirty cases of CCLs were identified among the 559 cases of FCC found. The ages of the patients ranged from 16 years to 63 years, the peak age of occurrence was in the 5th decade. The most common pattern found was Columnar Cell Change (CCC) which accounted for 66.7% of the cases. Columnar Cell Hyperplasia (CCH) accounted for 16.7%, and CCC and CCH occurred together in 16.7% of cases. No case of flat epithelial atypia (FEA) was found. The study showed that CCLs occur in Nigerian women. The FEA variant, the putative precursor of breast cancer, was not found among our cohort, most likely due to the benign surrogate lesion used for this study. FEA often co-exists with lobular neoplasia, and this entity would likely have been found if this study had included cases previously diagnosed with in situ and invasive lobular or ductal carcinoma. The age distribution of our patients was similar to that described among Caucasian women.Key words: Columnar Cell Lesions, Fibrocystic changes, Columnar Cell Change, Columnar Cell Hyperplasia, Flat Epithelial Atypia

Modelling and sensitivity analysis of a nanocomposite MFI-alumina based extractor-type zeolite catalytic membrane reactor for m-Xylene isomerization over Pt-HZSM-5 catalyst

In this paper, a report on modelling and sensitivity studies of a laboratory-scale extractor type catalytic membrane reactor having a nanocomposite MFI-alumina membrane tube as separation unit is presented. Meta-xylene isomerization over Pt-HZSM-5 catalyst was conducted in the reactor and the results compared with model output. Sensitivity of the model to changes in certain design parameters (membrane thickness, membrane porosity, membrane tortuosity and reactor size) was evaluated for in-depth understanding of the fundamental behaviour of the system during m-Xylene isomerization. The model output deviated from the experimental results with percentage errors of 17%, 29%, 0.05% and 19.5% for p-Xylene yield in combined mode, p-Xylene selectivity in combined mode, p-Xylene selectivity in permeate-only mode and m-Xylene conversion, respectively. Despite the discrepancy between the experimental results and the model output due to the to quality of data employed in the simulation and assumptions adopted for model simplification, the model could explain the behaviour of e-ZCMR during m-Xylene isomerization over Pt-HZSM-5 catalyst and also adaptable to e-ZCMRs of different configurations such as hollow fibre MFI-alumina membrane-based e-ZCMRs. However, acquisition of accurate kinetics and diffusion data through experimentation is essential to improve on the model. As expected, the sensitivity analysis revealed that membrane porosity, membrane tortuosity, membrane effective thickness and reactor size play a significant role on the performance of the e-ZCMR during the isomerization. Although, this model is of a preliminary nature, still it provides useful assistance in understanding the fundamental behaviour of e-ZCMR during m-Xylene isomerization and offers a platform upon which further modelling studies on m-Xylene isomerization in e-ZCMR can be built. © 2011 Elsevier B.V.Articl