THE EFFECT OF DEMULSIFIER AND DEWATERING AGENT ON SEPARATION OF PHASES FROM OILY WATER

Environmental pollution with crude oil and its derivates has become a growing problem due to their toxic and carcinogenic effects on live organisms. Proper collection and treatment of oily wastewaters is very important for prevention and disabling of harmful effects on the environment. The most important step in the oily wastewater treatment process is separation of oil and aqueous phase. Consequently, it is important to examine the conditions which enable the maximum separation effect and provide satisfactory quality of the aqueous phase before discharge into natural recipients. This paper examines the effects of temperature and addition of demulsifier and dewatering agent on phase separation in oily wastewaters. The best separation rate and the highest quantity of the aqueous phase are achieved with the addition of demulsifier in concentration of 500 mg/l and the dewatering agent in concentration of 500 mg/l at 60 °C. The quality of the aqueous phase after separation shows low values of mineral oils and high COD (Chemical Oxygen Demand) values due to the remaining demulsifier and dewatering agent in aqueous phase. For that reason it is necessary to use additional treatments, such as adsorption on active carbon or biological treatment before discharge into natural waters

INFLUENCE OF ZEOLITE PARTICLE SIZE AND INITIAL LEAD CONCENTRATION ON SORPTION KINETIC STUDY BY BATCH EXPERIMENTS

The effect of particle size and initial lead concentration on the kinetics of lead ions uptake onto natural zeolite has been examined by batch experiments. The uptake rate of lead ions increases with decreasing particle size and has no effect on the zeolite removal capacities. Also the removal capacities are not affected by initial lead concentrations. To identify the rate rate-determining step, experimental data have been tested by the Lagergren pseudo-first order, Ho pseudo-second order and Elovich reaction kinetic models, Vermeulen’s, Parabolic and Homogeneous diffusion models. For different lead concentrations and particle sizes the kinetic constants obtained have been changed and have consequently been excluded as relevant for the description of kinetics. Vermeulen´s and Homogeneous diffusion models have shown the best fitting with the experimental data, what confirms that intraparticle diffusion is rate-determining step of uptake process of lead ions onto natural zeolite

Evaluation of low-cost sorbents as potential materials for in situ remediation of water contaminated with heavy metals

The aim of this paper was to examine the possibilities of using various low-cost sorbents as material for permeable reactive barrier for efficient removing of lead, cadmium, copper and zinc from contaminated water. Natural zeolite (NZ), iron-modified zeolite (IMZ), apatite, concentrated apatite, kaolin and raw bentonite were examined. The batch test evaluation was used to investigate capturing of heavy metals from contaminated water onto sorbents, as well as retention strength of saturated sorbent. The change of pH values during saturation and leaching of heavy metals was performed in a slightly acidic to neutral area, confirming buffering abilities and environmental acceptability of all investigated sorbents as a material in PRB for protection of groundwater as the most valuable natural resources. The highest saturation ability towards all examined heavy metals was detected with raw bentonite and IMZ. Leaching of heavy metals at pH=2.94-2.98 was confirmed in all saturated sorbents, while at pH=6.07-6.46 it was not detected, except of Pb and Cd in raw bentonite. From the obtaned results, the recommendation for selection of sorbent for treatment of water contaminated with lead, cadmium, cooper and zinc is given

Kinetics and thermodynamics study of copper ions removal by natural clinoptilolite

137-144The process of removal of copper ions by means of clinoptilolite type natural zeolite has been studied as a function of the particle size and temperature. Results indicate that increase in temperature and decrease of particle size improves the removal of copper from aqueous solutions. The parabolic diffusion model is well described process in all examined range of time and it shows that the calculated diffusion coefficient increases with temperature. This increase is more visible at higher particle sizes what assume diffusion through zeolite particle as main mass transfer mechanism. The film diffusion model provides calculation of initial sorption rate (k´) and dimensionless parameter proportional to the diffusion film thickness (xi), in relation of particle size and temperature. Diffusion from the surface of zeolite particles through the micro and macro pores is well described with homogenous diffusion model, where change of the calculated overall rate constant is observed at »60 min of the process. This indicates the change of mass transfer rate through porous zeolite particle. The activation energy (Ea), activation enthalpy (H), activation entropy (S) and free energy of activation (G) have been calculated based on kinetic data. These thermodynamic parameters characterize process as diffusion dependent, weakly endothermic and nonspontaneous, where structural changes in structure of natural zeolite particle are not observed

Ružička days : International conference 16th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

Proceedings contains articles presented at Conference divided into sections: open lecture (1), chemical analysis and synthesis (3), chemical and biochemical engineering (8), food technology and biotechnology (8), medical chemistry and pharmacy (3), environmental protection (11) and meeting of young chemists (2)

Assessment of natural zeolite clinoptilolite for remediation of mercury-contaminated environment

The soil at ancient roasting sites in the surroundings of the Idrija mine (Slovenia) is highly contaminated with mercury. To assess the impact of mercury on groundwater by infiltration and find an eco-friendly remediation method, the leaching of mercury from the soil containing 1347 mg Hg/kg, followed by sorption of the total leached mercury on cost-effective natural zeolite (NZ) clinoptilolite, was performed. The leaching of soil in ultrapure water of pHo = 3.00–11.46 after 24 h resulted in the total leached mercury concentration in the range 0.33–17.43 µg/L. Much higher concentrations (136.9–488.0 µg/L) were determined after the first few hours of leaching and were high above the maximum permissible level in water for human consumption. The NZ showed very good sorption of the total leached mercury, with a maximum removal efficiency of 94.2%. The leaching of mercury in presence of the NZ resulted in a significant decrease of the total leached mercury (1.9–20.3 µg/L compared to 12.8–42.2 µg/L), with removal efficiencies up to 90.5%, indicating immobilization of mercury species. The NZ has a great potential for economically viable remediation of mercury-contaminated environment. However, efforts should be made in the further study of mercury leachability to reduce the mercury concentration in water to acceptable levels

Effect of the solid/liquid ratio on zinc and cadmium uptake on natural and iron-modified zeolite - Batch scale design

235-245Zinc and cadmium uptake on natural (NZ) and iron-modified zeolite (IMZ) has been investigated through the two sets of experiments, first one with varying S/L ratios at a constant initial metal concentration and second one with different initial metal concentrations at a single S/L ratio. Results confirm the importance of choosing an optimum S/L ratio in achievement of the maximum removal efficiency with the lowest zeolite mass. Two different methods for the design of batch reactor have been applied to overcome the effect of the S/L ratio. The first approach applied the operating line method with the Dubinin-Radushkevich isotherm, and the second one applied the Rayleigh's method of dimensional analysis. The excellent agreement between predicted and experimentally obtained results for the amount of metal removed per gram of zeolite as well as error functions confirm the applicability of both methods in the batch scale design independently of the S/L ratio

Application of mathematical empirical models to dynamic removal of lead on natural zeolite clinoptilolite in a fixed bed column

123-131This study examined the applicability of the mathematical empirical models by Bohart-Adams, Wolborska, Thomas and Yoon-Nelson on lead removal from aqueous solutions on a fixed bed of natural zeolite. Applicability of these models has been evaluated by fitting the experimental breakthrough curves with the curves obtained from the applied model. Experimental results have shown that the values of removal capacities calculated from model are close to the value of the experimentally obtained capacity at the exhaustion point. The Thomas and Yoon-Nelson models have shown excellent fit for all examined range of the breakthrough curves; therefore these models have been used for simulation of breakthrough curves for different bed depths and flow rates. The results show that the successful prediction is achieved when the empty bed contact time (EBCT) was in the experimentally confirmable range. Among all examined models, the Thomas model was found to be the most suitable one for simulation of the breakthrough curve of lead uptake on fixed bed of natural zeolite in a wide range of EBCT values

Modeling, Simulation, Optimization, and Experimental Verification of Mercury Removal onto Natural and Sulfur-Impregnated Zeolite Clinoptilolite—Assessment of Feasibility for Remediation of Mercury-Contaminated Soil

In this paper, a series of equilibrium and kinetic experiments of Hg(II) removal in a single-stage batch reactor on natural (NZ) and sulfur-impregnated zeolite (SZ) were performed. Batch sorption of Hg(II) on zeolites was studied using different isothermal and kinetic models. It was found to be best described by the Brouers-Sotolongo isotherm and the Vermeulen’s approximation, which were applied in optimizing the mass and contact time in two-stage cross-current and counter-current flow batch reactors based on the desired criterion of 99.9% removal efficiency. Mathematical models for minimizing zeolite mass and contact time were developed and experimentally verified. The optimum minimum masses of NZ and SZ were calculated for all systems, and a significant saving in SZ consumption was found when the counter-current design was applied. The toxicity characteristic leaching procedure (TCLP) was applied to mercury contaminated soil from the Idrija mine region in Slovenia to evaluate potential soil toxicity. The results showed that the soil is extremely contaminated and represents hazardous waste. The addition of zeolites significantly reduced the concentration of leached Hg, with the most satisfactory results obtained with SZ. It was found that at the lowest dose of 0.25 g of SZ, the leached Hg concentration was reduced below the maximum concentration criterion of 0.2 mg/L according to the TCLP test. This study revealed that SZ could be a potential sorbent for in situ remediation of mercury contaminated soil

A Mass Transfer Analysis of Competitive Binding of Pb, Cd, and Zn from Binary Systems onto a Fixed Zeolite Bed

The low-cost natural zeolite clinoptilolite was successfully applied for the competitive removal of Pb, Cd, and Zn from binary (Pb + Zn) and (Cd + Zn) aqueous solutions at different Pb/Zn and Cd/Zn concentration ratios. The obtained efficiency was in the range of 79.0⁻85.0%, and was similar for both systems, indicating that no loss in capacity was observed for six successive sorption-desorption cycles. In both systems, after the breakthrough, competition between the ions occurs, leading to overshooting in the Zn’s initial concentration, indicating displacement of already-bound Zn with Pb and Cd from the feeding solutions. The Zn exceeded its initial concentration up to 2.3 times in the presence of Pb, and up to 1.2 times in the presence of Cd. The film diffusion was pronounced as the slowest step responsible for the overall process rate. The overall mass transfer coefficient (Ka) shows higher values for the (Cd + Zn) system compared to the (Pb + Zn) one due to reduced competition and ions migration. An SEM-EDS analysis confirmed a higher amount of bound Pb and Cd compared to Zn, and a mapping analysis revealed the equal distribution of all ions onto the zeolite surface