The role of limestone and dolomite tailings’ particle size in retention of heavy metals from liquid waste

Purpose. The study aims at investigating the role of particle size of mineral tailings derived from limestone, limestone marble, dolomite and dolomitic marble in heavy metal adsorption, in both batch and fixed bed conditions, so as to estimate whether grinding and/or sieving is necessary for their utilization. Methods. Fractions of different particle size have been studied. Adsorption has been examined in batch conditions from solutions of 5 mg/l Cd, 5 mg/l Pb, 100 mg/l Cu, 100 mg/l Zn, and their mixed solution simulating electroplating wastewater, and also in fixed bed conditions. Findings. Total Cd and Cu adsorption is achieved on all the mineral fractions, whereas Pb and Zn show a difference up to 20% depending on particle size. Referring to the mixed solution, Cd and Zn adsorption is lower, whereas no significant differences in Cu and Pb adsorption are observed. Adsorption capacity rises up to 0.03 mg/g Cd, 0.60 mg/g Cu, 0.03 mg/g Pb, 0.60 mg/g Zn. In fixed bed conditions, metal adsorption greater than 93% is achieved. Furthermore, leaching not exceeding 4% indicates a good metal retention. Finally, Taguchi method has proven that the particle size effect is not so strong compared to other parameters, including solution concentration and time. Originality. The particle size of mineral tailings has not yet been investigated as a parameter affecting heavy metal adsorption. Furthermore, heavy metal adsorption has been examined from separate metal solutions and not from a mixed one. The present study aims at contributing to these two research fields. Practical implications. Τhe differences in adsorption between mineral tailings’ fractions with different particle size are not as high as to make grinding of minerals necessary.Мета. Дослідження впливу розмірів частинок у хвостах збагачення вапняку, вапняного мармуру, доломіту та доломітового мармуру на процес адсорбції важких металів у нерухомому шарі для оцінки доцільності технології подрібнення й/або просіювання в подальшому використанні металів. Методика. Для виконання досліджень зразки вапняку та доломіту доставлені компанією, що займається виробництвом і продажем готових бетонів, а також кар’єрами у Греції. Хімічний і мінералогічний склад зразків був визначений рентгенівської флуоресценцією (XRF, ARL ADVANT XP), рентгенівської дифракцією (XRD, Siemens D-500) та атомно-абсорбційною спектрометрією (AAS, VARIAN AA240FS). Для дослідження механізму адсорбції були виміряні наступні параметри: рН відповідно до ISO 6588, пористість і питома площа поверхні за допомогою N2-адсорбції (NOVA-2200, версія 6.11) та катіонообмінна ємність (CEC) відповідно до EPA 9081 на основі змішування зразка з надлишком розчину ацетату натрію, в результаті якого потім визначались додані катіони натрію для матричних катіонів. Для сорбційних експериментів були використані окремі розчини, які містять 5 мг/л Cd, 5 мг/л Pb, 100 мг/л Cu, 100 мг/л Zn, отримані з аналітичних стандартних розчинів Fluka. Після сорбційних досліджень зібрані сорбенти були піддані дослідженням вилуговування. Результати. У процесі досліджень була досягнута повна адсорбція Cd і Cu з усіх мінеральних фракцій, проте до 20% адсорбції Pb і Zn визначалася розмірами частинок. Встановлено, що величина адсорбції Cd і Zn нижче у змішаному розчині, але при цьому даний показник для Cu і Pb залишається без змін. Поглинаюча здатність зростає до 0.03 мг/г Cd, 0.60 мг/г Cu, 0.03 мг/г Pb, 0.60 мг/г Zn. В умовах нерухомого шару досягається до 93% адсорбції металів. Більше того, витік, що не перевищує 4%, свідчить про ефективність вилучення металів. Доведено за методом Тагучі, що вплив розмірів частинок не є настільки значним, щоб не враховувати роль інших параметрів, таких як концентрація розчину і час. Вилуговування іонів металів (Cd, Cu, Pb, Zn), що зберігаються на всіх мінералах після адсорбції в періодичних умовах, не перевищує 4% та вказує на те, що вони досить зберігаються на поверхні мінералів. Це є важливим результатом для подальшого використання мінералів у якості субстратів на полігонах. Наукова новизна. Вперше розміри частинок у хвостах збагачення мінералів розглянуті як параметр, який впливає на процес адсорбції важких металів, при цьому даний процес вивчений також щодо окремих розчинів металів, а не тільки їх суміші. Практична значимість. Виявленні відмінності у показниках адсорбції для фракцій частинок різного розміру не такі значущі, щоб обумовлювати необхідність їх подрібнення в технологічному процесі.Цель. Исследование влияния размеров частиц в хвостах обогащения известняка, известкового мрамора, доломита и доломитового мрамора на процесс адсорбции тяжелых металлов в неподвижном слое для оценки целесообразности технологии измельчения и/или просеивания в дальнейшем использования металлов. Методика. Для выполнения исследований образцы известняка и доломита доставлены компанией, занимающейся производством и продажей готовых бетонов, а также карьерами в Греции. Химический и минералогический состав образцов был определен рентгеновской флуоресценцией (XRF, ARL ADVANT XP), рентгеновской дифракцией (XRD, Siemens D-500) и атомно-абсорбционной спектрометрией (AAS, VARIAN AA240FS). Для исследования механизма адсорбции были измерены следующие параметры: рН в соответствии с ISO 6588, пористость и удельная площадь поверхности с помощью N2-адсорбции (NOVA-2200, версия 6.11) и катионообменная емкость (CEC) в соответствии с EPA 9081 на основе смешивания образца с избытком раствора ацетата натрия, в результате которого затем определялись добавленные катионы натрия для матричных катионов. Для сорбционных экспериментов были использованы отдельные растворы, содержащие 5 мг/л Cd, 5 мг/л Pb, 100 мг/л Cu, 100 мг/л Zn, полученные из аналитических стандартных растворов Fluka. После сорбционных исследований собранные сорбенты были подвергнуты исследованиям выщелачивания. Результаты. В процессе исследований была достигнута полная адсорбция Cd и Cu из всех минеральных фракций, однако до 20% адсорбции Pb и Zn определялась размерами частиц. Установлено, что величина адсорбции Cd и Zn ниже в смешанном растворе, но при этом данный показатель для Cu и Pb остается без изменений. Поглощающая способность возрастает до 0.03 мг/г Cd, 0.60 мг/г Cu, 0.03 мг/г Pb, 0.60 мг/г Zn. В усло-виях неподвижного слоя достигается до 93% адсорбции металлов. Более того, утечка, не превышающая 4%, свидетельствует об эффективности извлечения металлов. Доказано по методу Тагучи, что влияние размеров частиц не является настолько значительным, чтобы не учитывать роль других параметров, таких как концентрация раствора и время. Выщелачивание ионов металлов (Cd, Cu, Pb, Zn), сохраняющихся на всех минералах после адсорбции в периодических условиях, не превышает 4% и указывает на то, что они достаточно сохраняются на поверхности минералов. Это является важным результатом для дальнейшего использования минералов в качестве субстратов на полигонах. Научная новизна. Впервые размеры частиц в хвостах обогащения минералов рассмотрены как параметр, оказывающий влияние на процесс адсорбции тяжелых металлов, при этом данный процесс изучен также в отношении отдельных растворов металлов, а не только их смеси. Практическая значимость. Выявленные различия в показателях адсорбции для фракций частиц различного размера не столь значимы, чтобы обусловливать необходимость их измельчения в технологическом процессе.The present study did not originate under any of project and no funding was raised for research. However, we would like to thank especially Professor Angeliki Moutsatsou and the personal of the Laboratory of Inorganic and Analytical Chemistry of the Chemical Engineering School in the National Technical University of Athens for their various support during the experimental work required for the successful realization of the present study

Kinetics of Chromium(III) Transport Through a Liquid Membrane Containing DNNSA as a Carrier

Kinetics of Cr(III) ions transport through a bulk liquid membrane containing dinonylnaphthalenesulfonic acid (DNNSA) as a carrier, flowing over aqueous phases, has been examined. Special attention has been paid to the effect of the membrane’s velocity flow on the chromium concentration decrease in a feed phase. For the description of relationships of chromium(III) concentration in particular phases with the time, a model based on the assumption of consecutive first-order reactions was proposed. Satisfactory compatibility of experiments and model results have been obtained both for the membrane flow velocities below 0.0034 m·s−1 when the interfaces begin to fluctuate slightly and for low initial Cr(III) concentration in the feed phase

Assessment of Arthrobacter viscosus as reactive medium for forming permeable reactive biobarrier applied to PAHs remediation

Polycyclic aromatic hydrocarbons (PAHs) are significant environmental contaminants as they are present naturally as well as anthropogenically in soil, air and water. In spite of their low solubility, PAHs are spread to the environment, and they are present in surface water, industrial effluent or groundwater. Amongst all remediation technologies for treating groundwater contaminated with PAHs, the use of a permeable reactive biobarrier (PRBB) appears to be the most cost-effective, energy efficient, and environmentally sound approach. In this technology, the microorganisms are used as reactive medium to degrade or stabilize the contaminants. The main limits of this approach are that the microorganisms or consortium used for forming the PRBB should show adequate characteristics. They must be retained in the barrier-forming biofilm, and they should also have degradative ability for the target pollutants. The aim of the present work is to evaluate the viability of Arthrobacter viscosus as bioreactive medium for forming PRBB. Initially, the ability of A. viscosus to remove PAHs, benzo[a]anthracene 100 μM and phenanthrene 100 μM was evaluated operating in a batch bench-scale bioreactor. In both cases, total benzo[a]anthracene and phenanthrene removals were obtained after 7 and 3 days, respectively. Furthermore, the viability of the microorganisms was evaluated in the presence of chromium in a continuous mode. As a final point, the adhesion of A. viscosus to sepiolite forming a bioreactive material to build PRBB was demonstrated. In view of the attained results, it can be concluded that A. viscosus could be a suitable microorganism to form a bioreactive medium for PAHs remediation.This work has been supported by the Spanish Ministry of Economy and Competitiveness and FEDER Funds (Project CTM 2011-25389). Marta Pazos received financial support under the Ramon y Cajal programme and Marta Cobas under the final project master grant "Campus do Mar Knowledge in depth"

Neutron imaging of cadmium sorption and transport in porous rocks

Understanding fluid flow in rocks is crucial to quantify many natural processes such as ground water flow and naturally triggered seismicity, as well as engineering questions such as displacement of contaminants, the eligibility of subsurface waste storage, geothermal energy usage, oil and gas recovery and artificially induced seismicity. Two key parameters that control the variability of fluid flow and the movement of dissolved chemical species are (i) the local hydraulic conductivity, and (ii) the local sorption properties of the dissolved chemical species by the solid matrix. These parameters can be constrained through tomography imaging of rock samples subjected to fluid injection under constrained flow rate and pressure. The neutron imaging technique is ideal to explore fluid localization in porous materials due to the high but variable sensitivity of neutrons to the different hydrogen isotopes. However, until recently, this technique was underused in geology because of its large acquisition time. With the improved acquisition times of newly set-up neutron beamlines, it has become easier to study fluid flow. In the current set of experiments, we demonstrate the feasibility of in-situ 2D and 3D time-lapse neutron imaging of fluid and pollutant percolation in rocks, in particular that of cadmium salt. Cadmium is a hazardous compound that is found in many electronic devices, including batteries and is a common contaminant in soil and groundwater. It also exhibits higher contrast in neutron attenuation with respect to heavy water, and is therefore an ideal tracer. Time-lapse 2D radiographies and 3D neutron tomographies of the samples were acquired on two neutron beamlines (ILL, France and SINQ, Switzerland). We performed two sets of experiments, imbibition and injection experiments, where we imaged in-situ flow properties, such as local permeability and interactions between cadmium and the solid rock matrix. Our results indicate that even within these cm-scale porous rocks, cadmium transport follows preferential pathways, and locally interacts within the limestone samples. Our results demonstrate that the use of neutron imaging provides additional insights on subsurface transport of pollutants.Applied Geophysics and Petrophysic

Polyurethane composite adsorbent using solid phase extraction method for preconcentration of metal ion from aqueous solution

Polyurethane composite adsorbent polymeric material was prepared and investigated for selected solid-phase extraction for metal ions, prior to its determination by inductively coupled plasma optical emission spectrometry. The surface characterisation was done using Fourier transform infrared spectroscopy. The separation and preconcentration conditions of the analytes investigated includes influence of pH, sample loading flow rate, elution flow rate, type and concentration of eluents. The optimum pH for the highest efficient recoveries for all metal ions, which ranged from 70 to 85 %, is pH 7. The metal ions were quantitatively eluted with 5 mL of 2 mol/L HNO3. Common coexisting ions did not interfere with the separation. The percentage recovery of the metal ions ranged between 70 and 89 %, while the results for the limit of detection and limit of quantification ranged from 0.249 to 0.256 and 0.831 to 0.855, respectively. The experimental tests showed good preconcentration results of trace levels of metal ions using synthesised polyurethane polymer adsorbent composite

Behaviour of Cadmium(II) Ions on Cation-Exchange Resins

Cadmium is one of the most toxic heavy metals known and is considered inessential for living organisms. This element is found at low concentrations in natural environments, but human activities have led to increased levels in all continents. In the present study, the removal of cadmium(II) ions from aqueous solutions was investigated. Experimental investigations were undertaken using the ion-exchange resins Amberlite IR 120 (strongly acidic), Amberlite IRC 718 (weakly acidic and chelating), Lewatit TP 207 (weakly acidic and chelating) and Lewatit CNP 80 (weakly acidic). For investigations of the exchange equilibria, different amounts of resin material were contacted with a fixed volume of a cadmium ion-containing solution. Because the uptake of cadmium ions was mainly dominated by the pH of the liquid phase, the pH value was varied between 0 and 3 with sample sizes of 0.5–5.0 g in each series studied. The initial and final cadmium ion concentrations were measured by ICP–AES methods. Exchange equilibria were evaluated for strongly and weakly acidic resins via the surface complex formation theory that considers the sorption of ions as a local equilibrium reaction caused by the amphoteric behaviour of the surface. Application of this theory to exchange equilibria with ordinary and chelating weak acid exchange resins capable of releasing protons led to a comprehensive description of the systems. Binary equilibria were described by a logarithmic equilibrium parameter that was a linear function of the resin phase. For the evaluation of the equilibrium parameters, the generalized separation factors were calculated from the experimental data and plotted against the respective dimensionless resin loadings. Linear relationships were obtained in most cases although systematic deviations were found for small loadings

Chromium(III) Removal from Wastewaters by a Weakly Acidic Resin Containing Carboxylic Groups

As a conservative technology, ion exchange allows the removal and recycling of metals from liquid effluents. A process was applied for the removal of chromium(III) from wastewaters by ion exchange. This process was based on a weakly acidic cation-exchange resin (Amberlite IRC 86) capable of removing chromium(III) from the effluent, followed by selective separation and recovery during a regeneration procedure. Because of the difficult regeneration behaviour of the metal form of the carboxylate resin, special emphasis was given to the regeneration step of the resin where most of the practical problems were found. Five different regeneration procedures were adopted: elution with 1 M NaOH; elution with 1 M H 2 SO 4 ; elution with 1 M NaOH followed by 1 M H 2 SO 4 or vice versa; elution with NaOH followed by 1 M H 2 SO 4 /Na 2 SO 4 solution; and elution with alkaline H 2 O 2 /NaOH solutions followed by 1 M H 2 SO 4 . A non-conventional regenerant solution such as hydrogen peroxide in an alkaline medium seemed very promising. The anionic species formed (chromate) was eluted quantitatively from the cation-exchange resin and separated. The regeneration efficiency of chromium(III) was 89.5%. Influent chromium concentrations employed during the tanning process used in the leather industry were also considered. For this purpose, influent concentrations in the range 60–100 mg/l, service flow rates of 10 and 20 l/h and appropriate retention times were selected and experiments undertaken in a column system. The exhaustion step was carried out at 250 l/h with the recovery of chromium being 95.6%. The ion-exchange capacity of Amberlite IRC 86 was found to be 1.28 equiv/l. This study undertaken under laboratory conditions demonstrated that Amberlite IRC 86 resin was suitable for the removal of chromium(III) from wastewater

Determination of metal contents in some green leafy vegetables in Marmara region of Turkey

Abstract This study focused on the analysis of mineral and heavy metal contents of spinach, lettuce and parsley samples in different regions to investigate the risks of chronic exposure to heavy metal contamination. After the microwave digestion process, the metal contents of the samples (Na, Mg, Al, P, K, Ca, Fe, Cu, Zn, As, Se, Cd, Sn, Hg, Pb) were determined with the ICP-MS. Two parallel analysis samples were prepared from each sample, analyzed three times, and the mean values of the analyzes performed were reported. From the analysis, the order of finding heavy metals in the samples is Cu > Pb > Cd > As > Sn > Hg. The results were evaluated statistically and Cu, Pb, Cd, As and Sn values were found high in spinach samples (p < 0.05). According to the results of the analysis; the samples with the highest content of Cu, Pb and Cd in spinach samples are samples taken from Tekirdağ (5.1 ± 0.3 mg/kg), Edirne (0.106 ± 0.007 mg/kg) and Tekirdağ (0.080 ± 0.004 mg/kg), respectively. One of the important reasons for this is the increase in industrial areas in those regions. The results were compared with the certified reference materials, the quantities of analytes were determined to be compatible with the certificate values and the results of the analysis were proved to be correct

Removal and Recovery of Chromium from Solutions Simulating Tannery Wastewater by Strong Acid Cation Exchanger

The process in this study was conducted on removal of chromium(III) in a solution simulating a typical spent chrome tanning bath by the resin having matrix of styrene-divinylbenzene-based macroporous sulphonate, Amberjet 1200Na. The column experiments were carried out with the bed volumes of the resin as 751 mL and 1016 mL for different installation systems of the laboratory-scale pilot plant. The feeding solutions in the bed volumes of 200 and 190 were used for each installation system. The regeneration behaviour of the resin was determined by using reverse regeneration procedure with the solution of hydrogen peroxide in alkaline. The regeneration kinetics of the exhausted resin was examined with a range of the solutions having different concentration series of the alkaline hydrogen peroxide. The solutions of the basic chromium sulphate were recycled for each installation system following the regeneration cycles. The chromium ions in effluent were quantitatively eluted, and satisfactory removal of chromium(III) and recovery of chromium(VI) were achieved