Fluoride removal by a continuous flow electrocoagulation reactor

Long-term consumption of water containing excessive fluoride can lead to fluorosis of the teeth and bones. Electrocoagulation (EC) is an electrochemical technique, in which a variety of unwanted dissolved particles and suspended matter can be effectively removed from an aqueous solution by electrolysis. Continuous flow experiments with monopolar aluminium electrodes for fluoride removal were undertaken to investigate the effects of the different parameters such as: current density (12.5-50A/m(2)), flow rate (150-400 mL/min), initial pH (4-8), and initial fluoride concentration (5-25mg/L). The highest treatment efficiency was obtained for the largest current and the removal efficiency was found to be dependent on the current density, the flow rate and the initial fluoride concentration when the final pH ranged between 6 and 8. The composition of the sludge produced was analysed using the X-ray diffraction (XRD) spectrum. The strong presence of the aluminium hydroxide [Al(OH)(3)] in the above pH range, which maximizes the formation of aluminium fluoride hydroxide complex [Al(n)F(m)(OH)(3n-m)], is the main reason for defluoridation by electrocoagulation. The results obtained showed that the continuous flow electrocoagulation technology is an effective process for defluoridation of potable water supplies and could also be utilized for the defluoridation of industrial wastewater.     

On-line production of ferrate with an electrochemical method and its potential application for wastewater treatment – A review

A number of studies on the oxidation of various organic/inorganic contaminants by ferrate(VI) were reported in the 1980s and 1990s. The exploration of the use of ferrate(VI) for water and wastewater treatment has been well addressed recently. However, challenges have existed for the implementation of ferrate(VI) technology in practice due to the instability of a ferrate solution or high production cost of solid ferrate products. The research has been carried out aiming at the generation and application of ferrate(VI) in situ. This paper thus reviews ferrate chemistry and its overall performance as a water treatment chemical, discusses the factors affecting the ferrate yield efficiency using the electrochemical method, and finally, summarises the work on the production and use of ferrate in situ which is currently under study.     

The Effect of Water Harvesting Techniques on Runoff,Sedimentation, and Soil Properties

This study addressed the hydrological processes of runoff and sedimentation, soil moisture content, and properties under the effect of different water harvesting techniques (treatments). The study was conducted at three sites, representing environmental condition gradients, located in the southern part of the West Bank. For each treatment, the study evaluated soil chemical and physical properties, soil moisture at 30 cm depth, surface runoff and sedimentation at each site. Results showed that runoff is reduced by 65–85% and sedimentation by 58–69% in stone terraces and semi-circle bunds compared to the control at the semi-humid site. In addition, stone terraces and contour ridges significantly reduced the amount of total runoff by 80% and 73%, respectively, at the arid site. Soil moisture content was significantly increased by water harvesting techniques compared to the control in all treatments at the three study sites. In addition, the difference between the control and the water harvesting structures were higher in the arid and semi-arid areas than in the semi-humid area. Soil and water conservation, via utilization of water harvesting structures, is an effective principle for reducing the negative impact of high runoff intensity and subsequently increasing soil moisture storage from rainfall. Jessour systems in the valley and stone terraces were effective in increasing soil moisture storage, prolonging the growing season for natural vegetation, and decreasing the amount of supplemental irrigation required for growing fruit trees.     

Optimization of membrane-based CO2-removal from natural gas using simple models considering both pressure and temperature effects

Simple models for permeability and selectivity variations of the CO₂/CH₄ system in 6FDA-2,6-DAT membrane have been derived that include both temperature and pressure effects simultaneously in a single equation. The proposed models were used in MATLAB, for a membrane-based CO₂-removal process design for natural gas sweetening. The effects of the following factors on design parameters were examined: feed temperature, feed pressure and permeate pressure. The effect of permeate pressure was found to be very significant in the optimization process. In order to reduce hydrocarbon losses to below 2%, a two-stage membrane process was modeled and simulated in MATLAB, and the extent of desired hydrocarbon recovery was shown to be crucial in the optimization process. It has also been shown that there exist minima for the total required area of the two-stage membrane-based process, and as the CO₂ load increases in the feed, the position of these minima shift to higher values of methane loss.     

Assessing stress response of Stylophora pistillata towards oil and phosphate pollution in the Gulf of Aqaba,using molecular and biochemical markers

Crude oil (from oil terminal) and raw phosphate (from phosphate port) pollution are responsible for the lowered health conditions of coral reefs at their vicinity in the Jordanian coast of the Gulf of Aqaba. Both in situ incubations and ex situ laboratory exposure experiments were used to study the effects of those pollutants on corals, by using molecular and biochemical biomarkers in the coral Stylophora pistillata. For ex situ part of the experiment, crude oil and raw phosphate were added to a final concentration of 500?ppm for both pollutants. The DNA damage was assessed by Comet assay, while biochemical stress markers were reassessed by lipid peroxidation (LPO) test. Although the corals looked healthy from outside, the use of stress biomarkers indicated that they are under high pressure at the cellular level. The corals incubated with oil and phosphate had more DNA damage and LPO in comparison with the control samples. The results obtained suggest that the use of stress biomarkers can be used as important prognostic tools for examining the sub-lethal stress on corals before their death.     

Performance evaluation of a bipolar electrolysis/electrocoagulation (EL/EC) reactor to enhance the sludge dewaterability

The present study aimed to evaluate the performance of a bipolar electrolysis/electrocoagulation reactor designed to enhance the sludge dewaterability. The reactor was 15 L in volume, with two series of plates used in it; Ti/RuO₂ plates for the electrolysis of the sludge, and also aluminum and iron plates for electrocoagulation process. The dewaterability of the sludge was determined in terms of its capillary suction time (CST) and specific resistance to filtration (SRF), while the degree of sludge disintegration was determined based on the value of degree of sludge disintegration (DD_SCOD). The maximum reduction in CST and SRF was observed at a detention time of 20 min and a voltage of 30 V. However, increasing of both detention time and voltage significantly increased the values of CST and SRF even to an extent that they both exceeded those of the untreated sludge. The optimal degree of sludge disintegration achieved by the present study was 2.5%, which was also achieved at a detention time of 20 min and a voltage of 30 V. As reported previously, increased DD_SCOD values led to increasing CST and SRF values, due primarily to the disruption of the sludge flocs. According to the results from the present study, it can be concluded that simultaneous application of electrocoagulation and electrolysis is effective in enhancing the sludge dewaterability, because electrocoagulation helps to achieve a higher degree of sludge disintegration while maintaining the desired sludge dewaterability.     

Are deep eutectic solvents benign or toxic?

In continuation of investigation for environmentally benign protocol for new solvents termed deep eutectic solvents (DESs), it is herein reported results concerning the toxicity and cytotoxicity of choline chloride (ChCl) based DESs with four hydrogen bond donors including glycerine, ethylene glycol, triethylene glycol and urea. The toxicity was investigated using two Gram positive bacteria Bacillus subtilis and Staphylococcus aureus, and two Gram negative bacteria Escherichia coli and Pseudomonas aeruginosa. The cytotoxicity effect was tested using the Artemia salina leach. It was found that there was no toxic effect for the tested DESs on all of the studied bacteria confirming their benign effects on these bacteria. Nevertheless, it was found that the cytotoxicity of DESs was much higher than their individual components (e.g. glycerine, ChCl) indicating that their toxicological behavior is different. For our best knowledge this is the first time that toxicity and cytotoxicity of DESs were studied. The toxicity and cytotoxicity of DESs varied depending on the structure of components. Careful usage of the terms non-toxicity and biodegradability must be considered. More investigation on this matter is required.     

The use of date palm as a potential adsorbent for wastewater treatment: a review

Background

In tropical countries, the palm tree is one of the most abundant and important trees. Date palm is a principal fruit grown in many regions of the world. It is abundant, locally available and effective material that could be used as an adsorbent for the removal of different pollutants from aqueous solution.

Review

This article presents a review on the role of date palm as adsorbents in the removal of unwanted materials such as acid and basic dyes, heavy metals, and phenolic compounds. Many studies on adsorption properties of various low cost adsorbent, such as agricultural waste and activated carbons based on agricultural waste have been reported in recent years.

Conclusion

Studies have shown that date palm-based adsorbents are the most promising adsorbents for removing unwanted materials. No previous review is available where researchers can get an overview of the adsorption capacities of date palm-based adsorbent used for the adsorption of different pollutants. This review provides the recent literature demonstrating the usefulness of date palm biomass-based adsorbents in the adsorption of various pollutants.     

Review of environmental aspects and waste management of stone cutting and fabrication industries

Iran is the second largest stockholder of construction stones with 10 % of world production ;and there are more than 4000 stone cutting and fabrication industries (SCFIs). In the processing of raw stones, a considerable part of stone is turned into waste. Generated wastes include excess parts of different stones and sludge. The present paper reviews the state of SCFIs waste management using multiple data sources including site, analysis of effluent and sludge samples, and conducting interviews with people who are involved in 286 SCFIs in Qom and Tabriz. The results revealed that currently almost 35 to 52.5 % of raw stones were converted to solid wastes depending on stone cutting and processing methods, type of stones and their quality, which seemed a high percentage. Also, the effluents between 0.8 and 2.8 m³ were generated per ton of processed stone. Based on the analysis of heavy metals with atomic absorption spectroscopy, sludge samples contained a considerable amount of Pb, Cu, Cr, and Cd. It was also found that the lack of specific recycling, reuse and disposal programs and suitable supervision has led to uncontrolled disposal of stone wastes and sludge in different areas. However, there are good opportunities for reuse and recycling of the SCFIs wastes.     

Uptake of 14C-atropine and/or its transformation products from soil by wheat (Triticum aestivum var Kronjet) and their translocation to shoots

Plant uptake of toxins and their translocation to edible plant parts are important processes in the transfer of contaminants into the food chain. Atropine, a highly toxic muscarine receptor antagonist produced by Solanacea species, is found in all plant tissues and can enter the soil and hence be available for uptake by crops. The absorption of atropine and/or its transformation products from soil by wheat (Triticum aestivum var Kronjet) and its distribution to shoots was investigated by growing wheat in soil spiked with unlabeled or ¹⁴C-labeled atropine. Radioactivity attributable to ¹⁴C-atropine and its transformation products was measurable in plants sampled at 15 d after sowing (DAS) and thereafter until the end of experiment. The highest accumulation of ¹⁴C-atropine and/or its transformation products by plants was detected in leaves (between 73 and 90% of the total accumulated) with lower amounts in stems, roots, and seeds (approximately 14%, 9%, and 3%, respectively). ¹⁴C-Atropine and/or its transformation products were detected in soil leachate at 30, 60, and 90 DAS and were strongly adsorbed to soil, with 60% of the applied dose adsorbed at 30 DAS, plateauing at 70% from 60 DAS. Unlabeled atropine was detected in shoots 30 DAS at a concentration of 3.9 ± 0.1 μg kg^?1 (mean ± SD). The observed bioconcentration factor was 2.3 ± 0.04. The results suggest a potential risk of atropine toxicity to consumers.