Removal Of Chemical Pollutants Research Articles

Sequential Approach for Water Purification Using Seashell-Derived Calcium Oxide through Disinfection and Flocculation with Polyphosphate for Chemical Pollutant Removal.

Safe water supply is usually inadequate in areas without water treatment plants and even in a city under emergency conditions due to a disaster, even though safe water is essential for drinking and other various purposes. The purification of surface water from a river, lake, or pond requires disinfection and removal of chemical pollutants. In this study, we report a water purification strategy using seashell-derived calcium oxide (CaO) via disinfection and subsequent flocculation with polyphosphate for chemical pollutant removal. Seashell-derived CaO at a concentration (2 g L-1) higher than its saturation concentration caused the >99.999% inactivation of bacteria, mainly due to the alkalinity of calcium hydroxide (Ca(OH)2) produced by hydration. After the disinfection, the addition of sodium polyphosphate at 2 g L-1 allowed for the flocculation of CaO/Ca(OH)2 particles with adsorbing chemical pollutants, such as Congo red, dichlorodiphenyltrichloroethane, di(2-ethylhexyl)phthalate, and polychlorinated biphenyls, for removing these pollutants; purified water was obtained through filtration. Although this purified water was initially highly alkaline (pH ∼ 12.5), its pH decreased into a weak alkaline region (pH ∼ 9) during exposure to ambient air by absorbing carbon dioxide from the air with the precipitating calcium carbonate. The advantages of this water purification strategy include the fact that the saturation of CaO/Ca(OH)2 potentially serves as a visual indicator of disinfection, that the flocculation by polyphosphate removes excessive CaO/Ca(OH)2 as well as chemical pollutants, and that the high pH and Ca2+ concentrations in the resulting purified water are readily decreased. Our findings suggest the usability of seashell-derived material-polymer assemblies for water purification, especially under emergency conditions due to disasters.

Phenol removal from aqueous solution using advanced oxidation process enabled by a hybrid system: UV/H2O2/O3/TiO2

The need for healthy and pollution-free water is vital given the world’s industrialization and population explosion. The removal of chemical pollutants, especially phenol and phenolic compounds, from urban and industrial wastewaters is of particular importance due to their high water solubility and toxicity. Previous physicochemical techniques for phenol removal are no longer cost-effective. Advanced oxidation processes (AOPs) using various oxidizing agents have been recently recognized as an effective method for removing organic compounds through mineralization. The present work evaluated the phenol (100 ppm) removal from aqueous solutions through photooxidation systems of UV exposure, UV/TiO2, O3, O3/TiO2, H2O2, H2O2/UV, H2O2/TiO2, H2O2/TiO2/O3 and H2O2/TiO2/O3/UV. The results showed a decrease in the phenol concentration by almost half using UV, UV/TiO2, O3, O3/TiO2, H2O2, H2O2/UV and H2O2/TiO2 within 50 min. The phenol concentration reached 50 and 71 ppm using H2O2/TiO2/O3 system within 50 and 70 min, respectively. The UV/H2O2/O3/TiO2 system reduced the phenol concentration to zero after 40 min. The findings revealed that the AOP enabled by the UV/H2O2/O3/TiO2 combined system caused the complete removal of phenol, highlighting the capacity of the proposed system to remove toxic aromatic compounds such as phenol released during the wastewater treatment process.

Low-cost polyaniline/weathered basalt composites for methylene blue uptake from aqueous solutions

The removal of chemical pollutants from water using low-cost natural materials has been a recent trend in water treatment technologies. Therefore, the low-cost natural weathered basalt (WB) and its calcinated derivative at 900 °C/3h (calcinated weathered basalt, CWB) were used for the first time to synthesise innovative composites (C-RWB and C-CWB, respectively) via an oxidation polymerization process with polyaniline (PANI) using ammonium per sulphate (APS) as initiator. Characterizations of these adsorbents were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), FT-IR analysis, and Brunauer-Emmett-Teller (BET) surface area. As well, the potential use of these natural (WB), modified (CWB), and as-synthesised materials (C-RWB and C-CWB) in the purification of methylene blue (MB) from standard solutions at different experimental parameters was evaluated, and their efficiencies were compared. The pseudo-second-order equation with its very high determination coefficients (R2 > 0.996 for all adsorbents) fitted the MB uptake data better than the first-order one. In the meantime, intra-particle diffusion (IPD) was not the only driving rate in MB adsorption by the addressed adsorbents. Similarly, the MB adsorption data was well described using the Langmuir equation with maximum removal capacity (qmax) of 18.86, 10.18, 38.17, and 43.7 mg/g for RWB, CWB, C-CWB and C-RWB, respectively, at ambient temperature, better than the other applied models. The MB removal by the examined adsorbents was driven by electrostatic interaction and hydrogen bonding in mutable degree according to the dominating pH condition.

Flax shive as a source of activated carbon for adsorption of methylene blue

The application of carbon as an adsorbent is a well-known method of removal of chemical pollutants, including dyes, from waste waters. However, a lot of attention is now being paid to improving the adsorbent efficiency and searching for cheap precursors for activated carbon (AC) production. In this work, AC is obtained from flax shive by its physical and chemical activation with KOH. The pyrolysis process and mechanism of KOH activation are studied using thermogravimetric analysis. The methods of X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and low-temperature nitrogen adsorption are used to determine the AC characteristics. The AC ability to adsorb the methylene blue (MB) dye is studied. The effect of the properties of the synthesized AC on the MB equilibrium adsorption capacity is analyzed. The maximum BET surface area of the AC is equal to 1832.2 m2/g, which means its values lie in the range typical of industrial activated carbons. The maximum equilibrium adsorption capacity of MB is 464.2 mg/g. The AC adsorption capacity depends on the cellulose content in the flax shive and pore size distribution over the carbon matrix. The use of lignocellulosic biomass, namely flax shive, in the AC production is associated with solving environmental problems, such as agricultural waste recycling and disposal.

Composite Membrane and Evaluation on Separation Oil/Water

Background: The generation of wastewater contaminated with organic compounds, release or spill into these water bodies can lead to serious environmental problems. The removal of chemical pollutants in water presents itself as one of the central issues regarding the issue of environmental remediation. In this sense, membranes, haves gained increasing importance in the environmental area. Objective: This present study aims to develop a composite membrane using UHMWPE/LDPE/CTAC-HGC to be used for oil/water separation of wastewater effluents. Methods: The polymeric membrane and composite membrane were prepared by uniaxial dry compaction and sintering. Both hard green clay (HGC) and hard green clay organophilized with cetyl trimethyl ammonium chloride (CTAC-HGC) were characterized by X-ray Diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). UHMWPE, polymeric membrane and composite membrane were characterized by XRD and SEM. Result: The water flux through the composite membrane was evaluated using pure water as a permeate. The potential of the composite membrane to separate oil-water emulsions was tested. Conclusions: The composite membrane showed excellent removal of the oil, exhibiting removal of more than 99.60 %, evidencing the process of composite membrane separation as an alternative technology for the treatment of oil.

Tertiary Treatment of Livestock Wastewater in the Context of Alternative Water Resources for Sustainable Agriculture

The limited availability and quality of water resources are key issues of water management, and the protection and preservation of water resources are a requirement in the context of accelerated economic growth and principles of sustainable development. The experimental research presented in this paper is based on the need to identify alternative water sources and support unconventional wastewater treatment methods which would enable their reuse in areas affected by water scarcity and drought. Livestock wastewater contain significant levels of nutrients (nitrogen and phosphorus) and may represent an attractive water source for crop irrigation. This paper evaluates the efficacy of a proposed technological process for tertiary wastewater treatment consisting of two steps: electrochemical treatment for the removal of suspended and colloidal impurities and ozone disinfection. The experimental results showed higher efficiencies for the removal of chemical pollutants (92.5% COD, 79.3% BOD, 98.6% TSS, 41% residue saline) and significant inactivation of microorganisms (over 99.9% for total coliform bacteria and in some cases 100% for faecal coliform bacteria and faecal streptococci). The quality of the effluent complies with the regulations for wastewater use in agriculture and allows its reuse for different categories of use considering the required conditions for soil/crops. The successful application of treated wastewater to agricultural crops depends in a high extent on the good practices aimed on the improvement of crop yield and quality, optimisation of soil productivity and protection of the environment undertaken by the economic entities.

The use of immobilized microalgal bead concentrations in the removal of ammonium nitrogen from synthetic wastewater

Removal of chemical pollutants has been important in the treatment of wastewater. The effect of Chlorella vulgaris (microalgae) on the removal of ammonium nitrogen (NH4+) in synthetic wastewater (wastewater prepared in the laboratory) was investigated. C. vulgaris cells were immobilized in calcium alginate beads to allow diffusion of nutrients but retention of the cells. Concentration of C. vulgaris cells used to treat wastewater were equivalent to 20 g/l, 40 g/l and 80 g/l of wastewater and treatment was under laboratory conditions at 25±2°C. C. vulgaris was effective in the removal of NH4+ from wastewater; at the end of 24 hours of treatment, there was reduction in the initial concentration of NH4+ by 78% for 20 g/l. For 40 g/l treatment, there was 97% reduction in NH4+ and 91% reduction for 80 g/l treatment. After 43 hr of treatment, there was further reduction in NH4+ for 20 g/l (86%), and 80 g/l (93%) but 40 g/l (97%) remained constant. The concentration of C. vulgaris that showed the best activity in removing NH4+ -from wastewater was 40 g/l.Keywords: Microalgae, immobilize, microalgae, bead concentrations, ammonium nitrogen

Phosphorylated micro- vs. nano-cellulose: a comparative study on their surface functionalisation, growth of titanium-oxo-phosphate clusters and removal of chemical pollutants

Phosphorylation imparts cellulose (amorphous or crystalline) with original surface reactivity to bridge metal oxide clusters and to scavenge for chemicals.

Determination and calculation of solubility of bisphenol A in supercritical carbon dioxide

Supercritical fluid technology (SFT) as a new technique is very important for clean environment and removal of chemical pollutants. The lack of solubility data of solid solute in certain supercritical fluid is a great obstacle to the successful implementation of SFT. In this work, the solubility of bisphenol A in supercritical carbon dioxide was determined by the dynamic method at the temperatures ranging from 308 to 328K and pressure range of 11.0–21.0MPa. The effects of temperature and pressure on solubility were analyzed according to molecular motion theory. The solubility data were correlated using eight different semi-empirical models (Chrastil, Adachi–Lu, Kumar–Johnston, Tang, Sung–Shim, Bartle, Méndez Santiago–Teja and Yu). The comparison between different models was discussed. The thermodynamic properties (total enthalpy ΔH, enthalpy of sublimation ΔsubH and enthalpy of solvation ΔsolvH) of the solid solute were obtained.

Treatment of polluted landscape lake water and community analysis of ammonia-oxidizing bacteria in constructed wetland

Three lab-scale horizontal subsurface flow constructed wetlands (HSSF CWs) were installed to demonstrate the use of constructed wetlands as a viable low-cost treatment option to purify the polluted scenery water. The goals of this study were to determine the effectiveness of the wetland treatment technology in reducing contaminants in polluted natural water body and to characterize bacterial composition present in 3 constructed wetlands. Water samples were collected periodically for 12 months from three wetlands to determine the efficiency of the treatment system in removal of chemical pollutants. The reduction by the treatment was greatest for chemical oxygen demand (COD), total nitrogen and total phosphorus, but the removal of nutrients obviously varied with seasons. Plant uptake was highly responsible for nitrogen and phosphorus removal. Denaturing gradient gel electrophoresis (DGGE) was used to study the diversity of microbial community in the constructed wetland. Changes in the total bacterial community and ammonia-oxidizing bacterial composition were examined by DGGE and sequencing of polymerase chain reaction (PCR)-amplified fragments of the gene carrying the ammonia monooxygenase subunit A gene (amoA) recovered from matrix samples and DGGE bands. DGGE analysis of wetlands samples revealed that seasonal change had an effect on the diversity and composition of microbial communities in constructed wetlands. The sequence analysis showed ammonia-oxidizing bacteria (AOB) in constructed wetlands were uncultivable and the population of AOB had a higher percentage of Nitrosomonas-like sequences from wetlands, while no Nitrosospira-like sequences were found.

Arsenic-contaminated soils phytotoxicity studies with sunflower and sorghum

Background, Aim and Scope Environmental pollution caused by arsenic (As) is a major ecological problem. There has been intense worldwide effort to find As-hyperaccumulating plants that can be used in phytoremediation—the green-plant-assisted removal of chemical pollutants from soils. For phytoremediation, it is natural to prefer cultivated rather than wild plants, because their agriculture is well known. This study was conducted to evaluate the tolerance of common sunflower(Helianthus annuus L.) and sugar sorghum(Sorghum saccharatum Pers.) for soil-As contents of 10–100 mg As kg-1 soil, with sodium arsenite as a model contaminant.

Conservation of the African Great Lakes: A Limnological Perspective

The limnology of Lakes Malawi Tanganyika, and Victoria is discussed with the objective of examining how the physical, chemical, and biological properties of the lakes will determine the response of these ancient great lake ecosystems to human activities. Of the physical properties discussed, large dilution capacities and long flushing times can make the detection and removal of chemical pollutants in these lakes difficult. The outflows of all three lakes are small because of high evaporation losses, and as a result lake levels are responsive to climate changes that would alter evaporation:precipitation ratios. Increased nutrient input to these lakes will likely result in a decrease in the volume of oxygenated water and available fish habitat. Plankton community composition will also change, probably toward dominance by cyanobacteria. While the effects of eutrophication on fish production are difficult to predict, changes in plankton composition would almost certainly be accompanied by changes in fish community structure. Recent studies of water chemistry and plankton productivity in Lake Victoria provide evidence of possible eutrophication. Because land use has a diffuse but potentially large impact on these lakes, conservation strategies must take into account human activities within entire drainage basins. This requires cooperation between riparian countries and technological and financial input from the international community. An immediate need is the establishment of monitoring programs to determine the impact, real or potential, of human activities around the lakes.