Study of the mechanisms of heavy metal sorption by mineral apatite: the feasibility of soil and ground water remediation

U ovom radu izučavani su mehanizmi sorpcije teških metala korišćenjem dve forme minerala apatita: sintetičkog hidroksiapatita (HAP) i prirodnog apatita iz ležišta Lisina kod Bosilegrada (LA). Karakterizacija materijala je izvršena korišćenjem metode difrakcije x-zraka. Utvrđeno je da je sintetički apatit (HAP) čist hidroksiapatit molekulske formule Ca10(PO4)6(OH)2, dok je prirodni apatit (LA) smeša minerala kvarca, muskovita i fluorapatita. Mehanizmi sorpcije izučavani su korišćenjem teorijskog modela stabilnosti čvrste faze, kao i eksperimentalnim proučavanjem sorpcije olova iz vodenog rastvora. Teorijski matematički model stabilnosti čvrste faze baziran je na izračunavanju jon-jon interakcionih potencijala. Ovaj model upotrebljen je za procenu stabilnosti čvrste faze nastale reakcijom zagađujućih materija sa prirodnim i sintetičkim apatitom. Primenjeni model omogućava preliminarni izbor najpogodnijeg aditiva za imobilizaciju teških metala u zagađenom zemljištu ili podzemnim vodama sa stanovišta stabilnosti novonastale čvrste faze. Detaljno su razmotreni sledeći sistemi: Cd/HAP, Pb/HAP, Pb/prirodni apatiti i As/HAP. Na osnovu prikazanih rezultata predloženi su dominantni mehanizmi u procesima sorpcije zagađujućih materija u ispitivanim sistemima. U radu su izvršena eksperimentalna ispitivanja i modelovanje kinetike sorpcije olova iz vodenih rastvora korišćenjem prirodnog i sintetičkog apatita na tri temperature. Za modelovanje eksperimentalnih podataka korišćeni su kinetički modeli pseudo-prvog i pseudo-drugog reda. Utvrđeno je da model pseudo-drugog reda dobro opisuje kinetiku sorpcije olova u oba ispitivana sistema. Takođe su izvršena eksperimentalna ispitivanja adsorpcionih izotermi olova na hidroksiapatitu i prirodnom apatitu. Za analizu sorpcionih podataka korišćeno je pet modela adsorpcionih izotermi. Na osnovu primene ANOVA statističke analize utvrđeno je da Freundlich-ova adsorpciona izoterma najbolje opisuje eksperimentalne podatke u oba sistema. Analiza svih dobijenih rezultata ukazuje na mogućnost primene prirodnog apatita iz ležišta Lisina, kao jeftine polazne sirovine, za remedijaciju zemljišta i podzemnih voda zagađenih teškim metalima.In this work, the mechanisms of heavy metal sorption by two forms of mineral apatite were studied. The materials used include synthetic hydroxyapatite (HAP) and natural apatite from Lisina ore deposit (LA). The materials were characterized by x-ray diffraction. It was shown that synthetic apatite is pure hydroxyapatite, with molecular formula Ca10(PO4)6(OH)2, while natural apatite is a mixture of three minerals: quartz, muscovite and fluorapatite. The mechanisms were investigated using theoretical model of the solid matrix/impurity system stability as well as by experimental investigations of dissolved Pb sorption by HAP and LA. The theoretical model of the solid matrix/impurity system stability is based on ion-ion interaction potential calculation. This model was used to estimate the stability of the solid phase obtained by the reaction of heavy metals with synthetic and natural apatite. The applied model can be used for pre-selection of the most suitable amendment for heavy metal immobilization in polluted soils and ground water, based on the stability of the newly formed solid phase. The following systems were investigated in detail: Cd/HAP, Pb/HAP, Pb/natural apatites and As/HAP. Based on the results obtained, the dominant mechanisms involved in reactions in the investigated systems were suggested. In this work, experimental investigations and modeling of the kinetics of Pb sorption by natural and synthetic apatites were carried out at three temperatures. Two kinetic models were used: pseudo-first and pseudo-second order model. It was concluded that pseudo-second order model describes the kinetics of the processes in both systems best. Experimental investigations of the sorption isotherms were also carried out. Five sorption isotherms were used to model the experimental results. Using ANOVA statistical analysis it was concluded that Freundlich isotherm model described both systems with the greatest accuracy. Based on the analysis of all the results obtained, it can be concluded that natural apatite from Lisina ore deposit is a promising material for heavy metal remediation in polluted soils and ground water

High efficiency disperse dryer - an innovative process for drying of solutions, suspensions and pastes in a fluidized bed of inert particles

In this paper, an innovative fluidized bed dryer with inert particles is presented. The system can be used for drying of solutions, suspensions and pastes in order to obtain a powdered product. The experiments were performed in a pilot-scale dryer with a cylindrical column 0.215 m in diameter and 1.2 mm height, with glass spheres as inert particles. The material used for drying was CuSO4 solution. The effects of operating conditions on the dryer throughput and product quality were investigated. Main performance criteria, i.e. specific water evaporation rate, specific heat consumption and specific air consumption, were quantified. Nearly isothermal conditions were found due to thorough mixing of the particles. The energy efficiency of the dryer was also assessed. Simple heat and mass balances predicted the dryer performance quite well

Sušenje mulja iz procesa prečišćavanja otpadnih voda u fluidizovanom sloju inertnih čestica

Waste water treatment sludge is generated in increasing quantities, as the amount of treated municipal and industrial waste water increases. Also, the requirements concerning the conditions of sludge storage/landfill or reuse are growing. Due to these reasons, new solutions regarding sludge treatment, management and utilization are needed [1]. The benefits of drying waste water treatment sludge can be seen in several aspects: the dried sludge can be stored for longer periods of time and further used as an organic fertilizer, it can be a source of useful (active) microorganisms that can be reused in waste water treatment. Drying also enables incineration or co-incineration of sludge. Sludge drying process reduces mass and volume of the product, making its storage, transport, packaging and retail easier [2-4].ušenjem mulja iz procesa prečišćavanja otpadnih voda mogu se dobiti dva glavna upotrebljiva proizvoda: osušeni mulj može se skladištiti i koristiti kao organsko đubrivo, a može sadržati i aktivne (žive) mikroorganizme koji se ponovo mogu koristiti u tretmanu otpadnih voda. Sušenje suspenzija i pasta u fluidizovanom sloju inertnih čestica predstavlja atraktivnu alternativu ostalim postupcima sušenja u pogledu osnovnih kriterijuma za ocenu efikasnosti kao što su specifični kapacitet isparavanja, specifični utrošak toplote i specifični utrošak vazduha. Visoka efikasnost sušenja je rezultat velikih kontaktnih površina i velikih temperaturnih razlika između ulaznog i izlaznog toka vazduha za sušenje. Intenzivno mešanje inertnih čestica tokom agregativne fluidizacije obezbeđuje približno jednaku temperaturu u celoj zapremini sloja te ne postoji rizik od lokalnog pregrevanja. U radu su prikazani rezultati ispitivanja sušenja mulja na pilot postrojenju za sušenje suspenzija i pasta nominalnog kapaciteta isparavanja do20 kgH2O/h, čiji je centralni deo cilindrična kolona prečnika 215 mm sa fluidizovanim slojem staklenih sfera. Ispitivan je uticaj operativnih uslova na performanse sistema za sušenje i na kvalitet praškastog osušenog aktivnog mulja. Glavni cilj je da se odrede optimalne temperature sušenja mulja pri kojima bi korisni mikroorganizmu u mulju ostali aktivni (živi), a pri kojim aktivni mulj može da se koristi kao oragansko đubrivo. Izvršena je analiza efikasnosti sušenja sa stanovišta kapaciteta isparavanja i potrošnje vazduha u cilju boljeg sagledavanja performansi sistema za sušenje. Jednostavni bilansi mase i toplote adekvatno predviđaju radni režim sistema za sušenje u fluidizovanom sloju inertnog materijala

Ispitivanje dinamike granulacije praškastih materijala u fluidizovanom sloju

In this paper, experimental investigation of the dynamics of the process of fluidized bed granulation was performed, in order to find optimal process conditions and binder concentration to achieve the desired granules development. The experiments were performed in batch system using corn flour as starting material. Ten experiments were performed in which sucrose solution of different concentrations (20, 30, 35 and 40 %) was used as binder. The temperature of the system was kept constant during the granulation process and amounted to 40-50°C. Samples were taken from the fluidized bed at time intervals of 3 min. The dynamics of granulation was examined by determining three different factors (bulk density, moisure content and particle size distribution) for each of the samples. It has been found that bulk density continuously decreases during the granulation process, while in the drying phase it remains constant. Particle size distribution has shown that the average diameter of the projected surface increases uniformly during the process. By comparing all of the three investigated factors, it was shown that the best quality of granules is achieved using 35 % sucrose solution .U ovom radu izvršeno je eksperimentalno ispitivanje procesa mokre granulacije u fluidizovanom sloju u cilju pronalaženja optimalnih uslova izvođenja procesa i sastava veziva kojim će se ostvariti željena dinamika razvoja granula. Ispitivanje je izvršeno u šaržnom sistemu, a korišćeno je kukuruzno brašno kao polazni materijal. Izvršeno je 10 eksperimenata u kojima je kao vezivno sredstvo korišćen rastvor saharoze različitih koncentracija: 20, 30, 35 i 40 %. Temperatura je održavana konstantnom tokom procesa granulacije i iznosila je 40-50C. Uzorci su iz sloja uzimani u jednakim vremenskim intervalima od 3 min. Dinamika granulacije ispitivana je određivanjem tri različita faktora (nasipne gustina, vlažnosti i raspodele veličine čestica) za svaki od uzoraka. Utvrđeno je da nasipna gustina kontinualno opada tokom izvođenja procesa granulacije, dok u fazi sušenja ostaje konstantna. Raspodela veličina čestica je pokazala da srednji prečnik projektovane površine ravnomerno raste tokom procesa. Poređenjem sva tri ispitivana faktora pokazano je da se najbolji kvalitet granula postiže korišćenjem 35 % rastvora saharoze kao vezivnog sredstva.Related to: [http://cer.ihtm.bg.ac.rs/handle/123456789/3293

Ispitivanje dinamike granulacije praškastih materijala u fluidizovanom sloju

In this paper, experimental investigation of the dynamics of the process of fluidized bed granulation was performed, in order to find optimal process conditions and binder concentration to achieve the desired granules development. The experiments were performed in batch system using corn flour as starting material. Ten experiments were performed in which sucrose solution of different concentrations (20, 30, 35 and 40 %) was used as binder. The temperature of the system was kept constant during the granulation process and amounted to 40-50°C. Samples were taken from the fluidized bed at time intervals of 3 min. The dynamics of granulation was examined by determining three different factors (bulk density, moisure content and particle size distribution) for each of the samples. It has been found that bulk density continuously decreases during the granulation process, while in the drying phase it remains constant. Particle size distribution has shown that the average diameter of the projected surface increases uniformly during the process. By comparing all of the three investigated factors, it was shown that the best quality of granules is achieved using 35 % sucrose solution .U ovom radu izvršeno je eksperimentalno ispitivanje procesa mokre granulacije u fluidizovanom sloju u cilju pronalaženja optimalnih uslova izvođenja procesa i sastava veziva kojim će se ostvariti željena dinamika razvoja granula. Ispitivanje je izvršeno u šaržnom sistemu, a korišćeno je kukuruzno brašno kao polazni materijal. Izvršeno je 10 eksperimenata u kojima je kao vezivno sredstvo korišćen rastvor saharoze različitih koncentracija: 20, 30, 35 i 40 %. Temperatura je održavana konstantnom tokom procesa granulacije i iznosila je 40-50C. Uzorci su iz sloja uzimani u jednakim vremenskim intervalima od 3 min. Dinamika granulacije ispitivana je određivanjem tri različita faktora (nasipne gustina, vlažnosti i raspodele veličine čestica) za svaki od uzoraka. Utvrđeno je da nasipna gustina kontinualno opada tokom izvođenja procesa granulacije, dok u fazi sušenja ostaje konstantna. Raspodela veličina čestica je pokazala da srednji prečnik projektovane površine ravnomerno raste tokom procesa. Poređenjem sva tri ispitivana faktora pokazano je da se najbolji kvalitet granula postiže korišćenjem 35 % rastvora saharoze kao vezivnog sredstva.Related to: [http://cer.ihtm.bg.ac.rs/handle/123456789/3293

Momentum-heat-mass transfer analogy in gas-solid packed bed at elevated temperatures

The experimental values of the friction factor (fp) at ambient and elevated temperatures as well as of the heat transfer coefficient (hp) were used to establish the analogy among momentum and heat transfer in gas-solid packed beds of mono-sized spherical glass particles, as jH=fp/22 or jHε=fp/50. Also, Chilton-Colburn type of momentum-mass transfer analogy was confirmed. These findings are valid for the range of the modified Reynolds number Re’p≈20-130. The experiments related to fp were performed by measuring the pressure drop across the packed bed of particles (0.58, 0.92, 1.04, 1.20, 1.94, 2.98, 3.91 and 4.91 mm diameters) heated to the desired temperature by hot air (temperatures from 20ºC to 350ºC). The range of gas superficial velocity was from 0.05 to 0.99 m/s and the bed porosities were from 0.357 to 0.430. The experiments related to hp were performed by recording the temperatures of the cold aluminium test spheres (6, 12 and 20 mm dimeters) with embedded K-type (Ni/Al) thermocouples, immersed into the hot packed bed of particles (1.20, 1.94 and 2.98 mm diameters at temperatures from 100 to 300ºC) until the thermal equilibrium was reached. The superficial gas velocity and bed porosity varied from 0.30 to 0.79 m/s and from 0.392 to 0.406, respectively.  New correlation for prediction of the heat transfer factor has been proposed in the form jHε=0.30(Re’p)-0.30.The analogies defined in this way leave the possibility of determining the value of the heat and mass transfer coefficients on the basis of the value of the friction factor, which is more common in the literature

Effects of different mechanical treatments on structural changes of lignocellulosic waste biomass and subsequent Cu(II) removal kinetics

In this paper, the character of structural changes induced by different mechanical treatments to Prunus persica stones (PSs), and its subsequent effect on biosorption kinetics of Cu(II) were investigated. PSs were processed in vibratory disk mill (PS-V) and ultra-centrifugal mill (PS-C) and characterized by XRD, BET, SEM and FTIR spectroscopy. It was shown that PS-V was smaller and more reactive with less crystallinity index and hydrogen bond intensity compared to PS-C. In opposite, surface area of the PS-C was bigger than that of the PS-V. The total pore volume was about threefold, while the volume of micro pores was 9.29 times higher in PS-Cs than in PS-Vs. The kinetics of Cu(II) biosorption by both PSs was tested through various kinetic models: pseudo-first and pseudo-second order rate equations, Elovich equation, Boyd model, Weber–Morris and Urano–Tachikawa intraparticle diffusion model. For both sample types, Cu(II) biosorption occurred through combination of intraparticle and film diffusion mechanism, while kinetic results were best described by the pseudo-second order kinetic model. At the same time, the results indicated that together with kinetic rate the biosorption capacity of PS-C (21.20 mg g−1) was higher than that of PS-V (16.30 mg g−1). Mechanical activation like crushing and grinding will change material particle size, specific surface area and porosity, as well as its crystallinity. However, this paper elucidates that such physical structural changes will impact on heavy metal ions removal efficiency. This investigation suggests that the type of size reduction in lignocellulosic biosorbent preparation plays a very important role in overall biosorption performance, so it should be carefully considered every time when the mechanical treatment of material is necessary to be applied

Izučavanje mehanizama sorpcije teških metala apatitom : mogućnost primene u remedijaciji zagađenog zemljišta i podzemnih voda

In this work, the mechanisms of heavy metal sorption by two forms of mineral apatite were studied. The materials used include synthetic hydroxyapatite (HAP) and natural apatite from Lisina ore deposit (LA). The materials were characterized by x-ray diffraction. It was shown that synthetic apatite is pure hydroxyapatite, with molecular formula Ca10(PO4)6(OH)2, while natural apatite is a mixture of three minerals: quartz, muscovite and fluorapatite. The mechanisms were investigated using theoretical model of the solid matrix/impurity system stability as well as by experimental investigations of dissolved Pb sorption by HAP and LA. The theoretical model of the solid matrix/impurity system stability is based on ion-ion interaction potential calculation. This model was used to estimate the stability of the solid phase obtained by the reaction of heavy metals with synthetic and natural apatite. The applied model can be used for pre-selection of the most suitable amendment for heavy metal immobilization in polluted soils and ground water, based on the stability of the newly formed solid phase. The following systems were investigated in detail: Cd/HAP, Pb/HAP, Pb/natural apatites and As/HAP. Based on the results obtained, the dominant mechanisms involved in reactions in the investigated systems were suggested. In this work, experimental investigations and modeling of the kinetics of Pb sorption by natural and synthetic apatites were carried out at three temperatures. Two kinetic models were used: pseudo-first and pseudo-second order model. It was concluded that pseudo-second order model describes the kinetics of the processes in both systems best. Experimental investigations of the sorption isotherms were also carried out. Five sorption isotherms were used to model the experimental results. Using ANOVA statistical analysis it was concluded that Freundlich isotherm model described both systems with the greatest accuracy. Based on the analysis of all the results obtained, it can be concluded that natural apatite from Lisina ore deposit is a promising material for heavy metal remediation in polluted soils and ground water.U ovom radu izučavani su mehanizmi sorpcije teških metala korišćenjem dve forme minerala apatita: sintetičkog hidroksiapatita (HAP) i prirodnog apatita iz ležišta Lisina kod Bosilegrada (LA). Karakterizacija materijala je izvršena korišćenjem metode difrakcije x-zraka. Utvrđeno je da je sintetički apatit (HAP) čist hidroksiapatit molekulske formule Ca10(PO4)6(OH)2, dok je prirodni apatit (LA) smeša minerala kvarca, muskovita i fluorapatita. Mehanizmi sorpcije izučavani su korišćenjem teorijskog modela stabilnosti čvrste faze, kao i eksperimentalnim proučavanjem sorpcije olova iz vodenog rastvora. Teorijski matematički model stabilnosti čvrste faze baziran je na izračunavanju jon-jon interakcionih potencijala. Ovaj model upotrebljen je za procenu stabilnosti čvrste faze nastale reakcijom zagađujućih materija sa prirodnim i sintetičkim apatitom. Primenjeni model omogućava preliminarni izbor najpogodnijeg aditiva za imobilizaciju teških metala u zagađenom zemljištu ili podzemnim vodama sa stanovišta stabilnosti novonastale čvrste faze. Detaljno su razmotreni sledeći sistemi: Cd/HAP, Pb/HAP, Pb/prirodni apatiti i As/HAP. Na osnovu prikazanih rezultata predloženi su dominantni mehanizmi u procesima sorpcije zagađujućih materija u ispitivanim sistemima. U radu su izvršena eksperimentalna ispitivanja i modelovanje kinetike sorpcije olova iz vodenih rastvora korišćenjem prirodnog i sintetičkog apatita na tri temperature. Za modelovanje eksperimentalnih podataka korišćeni su kinetički modeli pseudo-prvog i pseudo-drugog reda. Utvrđeno je da model pseudo-drugog reda dobro opisuje kinetiku sorpcije olova u oba ispitivana sistema. Takođe su izvršena eksperimentalna ispitivanja adsorpcionih izotermi olova na hidroksiapatitu i prirodnom apatitu. Za analizu sorpcionih podataka korišćeno je pet modela adsorpcionih izotermi. Na osnovu primene ANOVA statističke analize utvrđeno je da Freundlich-ova adsorpciona izoterma najbolje opisuje eksperimentalne podatke u oba sistema. Analiza svih dobijenih rezultata ukazuje na mogućnost primene prirodnog apatita iz ležišta Lisina, kao jeftine polazne sirovine, za remedijaciju zemljišta i podzemnih voda zagađenih teškim metalima

In situ lead stabilization using natural and synthetic apatite

In this work, mineral apatite was investigated for the remediation of lead contamination. Two different apatite minerals were used: synthetic apatite, Ca10(PO4)6(OH)2 (hereafter denoted as HAP) and natural apatite from Lisina, near Bosilegrad, Serbia (hereafter denoted as LA). Phosphate ore from Lisina deposit consists of 43.3 % apatite in the form of fluorapatite, Ca10(PO4)6(F)2. Sorption properties of HAP and LA were investigated. The results show that both of these minerals are effective in lead removal from the water solution. Sorption capacity of HAP obtained in this experiment is 0.216 mmol Pb/g HAP, while the value for LA is 0.162 mmol Pb/g LA. Modeling of these systems was conducted using Visual Minteq computer program. The values obtained from the computer simulation were compared to experimental values

Aqueous Pb sorption by synthetic and natural apatite: Kinetics, equilibrium and thermodynamic studies

Natural apatites represent a cost effective soil amendment, which can be used for in situ reduction of lead bioavailability and mobility. In our previous work, we selected Lisina apatite (LA) as a promising natural mineral for lead immobilization based on theoretical predictions. This study investigated the adsorption equilibrium and kinetics of aqueous Pb sorption onto Lisina apatite and synthetic hydroxyapatite (HAP) at different temperatures. XRD analysis indicated that LA consists of three minerals: fluorapatite, quartz and muscovite. After reaction with a Pb solution, only FA peaks were changed, confirming that fluorapatite present in LA is responsible for Pb sorption. Sorption experiments confirmed that both LA and HAP are effective in Pb removal. Langmuir, Freundlich, Temkin, Koble-Corrigan and Redlich-Peterson isotherm models were applied to experimental data. The kinetics of the sorption process on both minerals was well characterized by the pseudo-second order reaction rate. Results indicate that Pb immobilization by HAP is a two-step process: the first rapid phase, possibly surface complexation and secondary dissolution of HAP and precipitation of pyromorphite. The sorption of Pb by Lisina apatite is also a two-step process, but the reaction mechanisms are more complicated and need further research as the results indicate that different mechanisms dominate at different temperatures. The values of thermodynamic equilibrium constants and Gibbs free energy were also calculated. The values of AG obtained confirm the feasibility of both HAP and LA as effective sorbents of the Pb ion