Monitoring of Heavy Metal Pollution of Groundwater in a Phreatic Aquifer in Mersin-Turkey

In this study, heavy metal contents of groundwater from the Mersin aquifer were determined with photometric methods and used to determine the main factors controlling the pollution of groundwater in the area. Using MapInfo GIS software, spatial analysis and integration were carried out for mapping drinking water quality in the basin. From the photometric heavy metal analysis, it is inferred that the excess concentration of Fe, Ni, Mn, Mo and Cu at some locations is the cause of undesirable quality for drinking purposes. Similarly, the EC thematic map shows that considerable areas in the basin are having high salinity hazards. The reason for excess concentration of various heavy metals is the industrial activities and petroleum pipelines and salinity levels show the sea water intrusion.     

Small‐Capacity Gold Production Tests From Waste Desktop Computers

This article describes a procedure for the hydrometallurgical recovery of gold from waste computer printed circuit boards (PCBs) and central processing units (CPUs). The wastes processed within the recovery installation described in this article were derived from desktop computers, the parts of which were manually sorted to select those components found to be rich in gold content. X‐ray fluorescence measurements showed that considerable amounts of gold are contained in the “finger” terminals of the PCBs as well as in the CPUs. This article describes the chemical processes for recovering gold from these parts. In addition, the article covers the emissions control apparatus that is capable of eliminating the nitrogen oxides (NOx) and sulfur dioxide (SO2) emissions produced by the recovery process. The main costs arising from the overall procedure are for personnel utilization. Approximately 60 work hours from one worker are required to process 1.75–1.85 tons of unprocessed desktop computer waste to produce gold in the form of sediments. The quantity of gold recovered from this amount of waste computers can reach up to 35 grams with a standardized purity of 21 karats. The overall recovery procedure takes eight consecutive calendar days to accomplish.     

Microwave-assisted synthesis of hydroxyapatite for the removal of lead(II) from aqueous solutions

Purpose

This study has the objective to evaluate the lead(II) removal capacity of hydroxyapatite powder synthesized by microwave as an alternative method to decrease production time and cost.

Methods

Hydroxyapatite (HA) was synthesized by a microwave-assisted precipitation method using calcium nitrate and ammonium hydrogen phosphate as calcium and phosphorus sources, respectively. X-ray diffraction and Fourier transform infrared results clearly revealed that the resulting powder was HA with high purity and crystallinity. The obtained powder was used for the removal of lead(II) from aqueous solutions. The effects of pH, amount of adsorbent, initial lead(II) concentration, and contact time were studied in batch experiments.

Results

In the adsorption experiments, maximum lead(II) retention was obtained at pH 6. Adsorption equilibrium was established after 40 min. It was found that the adsorption of lead(II) on HA was correlated well (R ²?=?0.958) with the Freundlich equation for the concentration range studied. Both ion exchange and adsorption process were thought to exist in the removal process.

Conclusions

This study indicates that easily and rapidly synthesized HA by microwave-assisted precipitation method could be used as an efficient adsorbent for removal of lead(II) from aqueous solutions.     

Determination of some mineral contents of prickly pear (Opuntia ficus-indica L.) seed flours

The aim of this study was to determine some mineral contents of prickly pear (Opuntia f?cus-indica L.) seeds collected from different locations. The mineral contents of seeds were established by inductively coupled plasma atomic emission spectrometry. All the seeds contained Ca, K, Mg and P at high levels. Calcium content ranged between 268.5 (sample no. 11) and 674.8 ppm (sample no. 4). The level of K changed between 346.7 (sample no. 1) and 676.1 ppm (sample no. 13). Phosphorus content of seeds varied between 1,173.6 (sample no. 14) and 1,871.3 ppm (sample no. 1). It is apparent that seeds are good sources of the macro and micro minerals and can be consumed as a food ingredient to provide nutrition.     

Potential utilization of burned wood in manufacture of medium density fiberboard

The potential utilization of burned wood in the manufacture of medium density fiberboard (MDF) was investigated. For this aim, the MDF panels were made of various mixtures of burned pine wood (Pinus sylvestris L.), unburned beech (Fagus orientalis L.) and oak (Ouercus robur L.) woods under commercial conditions in an MDF company. The mixture ratio of the unburned beech and oak woods to the burned pine wood were 50/50 wt%. The mixing ratios of burned wood chips with unburned wood chips were 0:100, 25:75, 50:50, 75:25 and 100:0, %, respectively. A commercial urea–formaldehyde resin was used as a binder. The physical properties measured in the investigation included density and thickness swelling, while the mechanical properties examined were bending strength, modulus elasticity, internal bond, screw holding ability perpendicular to the plane of panel, and janka hardness perpendicular to the plane of the panel. Surface roughness and color of the panels were also measured. The results indicated that all the panels met the mechanical properties of general-purpose MDF requirements of EN 622-5. The surface roughness of the MDF panels containing burned wood decreased with increasing burned wood content but remained higher than the control panels. The dimensional stability of the MDF panels decreased with the incorporation of burned wood fibers as compared with the control MDF panels.     

Estimating soil temperature using neighboring station data via multi-nonlinear regression and artificial neural network models

The aim of this study is to estimate the soil temperatures of a target station using only the soil temperatures of neighboring stations without any consideration of the other variables or parameters related to soil properties. For this aim, the soil temperatures were measured at depths of 5, 10, 20, 50, and 100 cm below the earth surface at eight measuring stations in Turkey. Firstly, the multiple nonlinear regression analysis was performed with the “Enter” method to determine the relationship between the values of target station and neighboring stations. Then, the stepwise regression analysis was applied to determine the best independent variables. Finally, an artificial neural network (ANN) model was developed to estimate the soil temperature of a target station. According to the derived results for the training data set, the mean absolute percentage error and correlation coefficient ranged from 1.45% to 3.11% and from 0.9979 to 0.9986, respectively, while corresponding ranges of 1.685–3.65% and 0.9988–0.9991, respectively, were obtained based on the testing data set. The obtained results show that the developed ANN model provides a simple and accurate prediction to determine the soil temperature. In addition, the missing data at the target station could be determined within a high degree of accuracy.     

Study of the toxicity of diuron and its metabolites formed in aqueous medium during application of the electrochemical advanced oxidation process "electro-Fenton"

Diuron (N'-[3,4-dichlorophenyl]-N,N-dimethylurea) is a herbicide belonging to the phenylurea family, widely used to destroy weeds on uncultivated surfaces. Because of its toxicity for aquatic organisms and suspicion of being carcinogenic for humans, diuron is the object of growing environmental concern. Therefore, we have developed the electro-Fenton method, an electrochemical advanced oxidation process (EAOP), to degrade diuron in aqueous medium, and we have studied the evolution of the toxicity of treated solution during the process. Indeed, the EAOPs catalytically generate hydroxyl radicals that oxidize the persistent organic pollutants, and can ultimately destroy and mineralize them. But, sometimes, relatively toxic organic metabolites are formed during the oxidation reaction. In this work, the evolution of toxicity of diuron aqueous solutions was studied at different initial concentrations, during treatment by the electro-Fenton method. Samples were collected at various electrolysis times and mineralization degrees during the treatment. The toxicity of the samples was measured using the bacteria Vibrio fischeri (Microtox) and the green alga Scenedesmus obliquus. Our results demonstrated that the toxicity of diuron aqueous solutions (concentrations=3.0-27.6 mg L(-1)) varied considerably with time. The formation and disappearance of several metabolites, having toxicity often stronger than that of the initial herbicide, were observed. To improve the efficiency of water decontamination, the electro-Fenton method should be applied during a time long enough (several hours) and at relatively high electrolysis current (I=250 mA) to reach a nearly complete mineralization of the herbicide in the aqueous medium.     

Soil amendments, plant age, and intercropping impact p,p'-DDE bioavailability to Cucurbita pepo

Field experiments were conducted to optimize the phytoextraction of weathered p,p'-DDE (p,p'-dichlorodiphenyldichloroethylene) by Cucurbita subspecies. The effects of two soil amendments, mycorrhizae or a biosurfactant, on p,p'-DDE accumulation was determined. Also, p,p'-DDE uptake was assessed during plant growth (12, 26, 38, and 62 d), and cultivars that accumulate weathered p,p'-DDE were intercropped with cultivars known not to have that ability. Cucurbita pepo L. ssp. pepo accumulated large amounts of the contaminant, having stem bioconcentration factors, amounts of p,p'-DDE translocated, and contaminant phytoextraction that were 14, 9.9, and 5.0 times greater than C. pepo L. ssp. ovifera (L.) D.S. Decker, respectively. During 62 d, the stem BCF (bioconcentration factor) for p,p'-DDE in subspecies pepo remained constant and the total amount of contaminant accumulated was correlated with plant biomass (r(2) = 0.86). For subspecies ovifera, the stem BCF was highest at 12 d (1.5) but decreased to 0.39 by 62 d, and p,p'-DDE removal was not correlated with plant biomass. Mycorrhizal inoculation increased p,p'-DDE accumulation by both subspecies by an average 4.4 times. For subspecies pepo, mycorrhizae increased the percentage of contaminant extracted from 0.72 to 2.1%. Biosurfactant amendment also enhanced contaminant accumulation by both subspecies, although treatment reduced subspecies ovifera biomass by 60%. The biosurfactant had no effect on the biomass of subspecies pepo, increased the average contaminant concentration by 3.6-fold, and doubled the overall amount of p,p'-DDE removed from the soil. Soil amendments that enhance the mobility of weathered persistent organic pollutants will significantly increase the amount of contaminant phytoextraction by Cucurbita pepo.     

Degradation of PVC Containing Mixtures in the Presence of HCl Fixators

Degradation of a model polymer mixture (PVC/PS/PE) and a waste polymer mixture in the presence of HCl fixators (Red Mud, precipitated CaCO₃ and dolamite) was studied using thermal gravimetric analysis (TGA) and a cycled-spheres-reactor. The experiments in cycled-spheres reactor model were performed by stepwise pyrolysis. Liquid products and HCl from each step were collected separately. For the model polymer mixture, the precipitated CaCO₃ showed the best effect on the fixation of evolved HCl and the reduction of chlorine content in the liquid products whereas RM yielded the best result for the waste polymer mixture. In addition, using HCl fixator also affected the degradation of both types of polymer mixture, leading to the formation of more gaseous and less residue.     

Characterization of different types of electronic waste: heavy metal,precious metal and rare earth element content by comparing different digestıon methods

Journal of Material Cycles and Waste Management - Electronic waste is one of the fastest-growing waste streams. The content of this waste has critical importance for the development or adoption of...