Synthesis, characterisation and application iron and manganeous based sorbents for arsenic removal from water

Prisusutvo  arsena  u  podzemnim  vodama,  koje  se  primenjuju  za vodosnabdevanje stanovništva je globalan problem. Različiti  konvencionalni procesi  se primenjuju  za  uklanjanje  arsena iz vode, uključujući koagulaciju i flokulaciju,  sorpciju,  membransku  filtraciju  i  jonsku  izmenu.  Uzimajući  u obzir relativnu nisku cenu, jednostavnu kontrolu procesa i održavanje, visok stepen uklanjanja arsena, sorpcija se smatra jednom od najpodobnijih tehnika za uklanjanje arsena u tretmanu vode za piće. Premda su na tržištu dostupni različiti  sorbenti  za  uklanjanje  arsena,  postoji  potreba  za  iznalaženjem  i razvojem  novih  low-cost  sorbenata,  a  kojima  bi  se  pak  mogao  obezbediti visok stepen uklanjanja oba oksidaciona oblika  arsena,  i  As(III) i As(V). Cilj ovog rada bio je usmeren na sintezu i karakterizaciju novih sorbenata na bazi gvožđa  i  mangana  odnosno  Fe-Mn  binarnog  oksida,  ispitivanje  njihovog potencijala  za  uklanjanje  arsena  iz  vode  i  utvrđivanje  da  li  novosintetisani sorbenti po pitanju efikasnosti, mogu konkurisati postojećim komercijalnim i široko korišćenim sorbentima u tretmanima voda. Metodom  precipitacije,  sintetisani  su  Fe-Mn  binarni  oksidi  sa  različitim Fe:Mn  molskim  odnosima  1:1,  3:1,  6:1  i  9:1,  dok  su  kombinacijom heterogene  nukleacione  tehnike  i  precipitacije,  sintetisana  i  četiri  sorbenta magnetnih  svojstava  (Mag,  Mag-Fe,  Mag-Mn,  Mag-FeMn).  Modifikacijom biopolimera  Chitosana  i  GAC,  sa  Fe-Mn  binarnim  oksidom,  razvijena  su preostala  dva  materijala  Chit-FeMn,  odnosno  GAC-FeMn.  Sintetisani sorbenti su karakterisani različitim tehnikama i metodama (SEM/EDS, XRD,FTIR, BET).Fizičko-hemijskom karakterizacijom sintetisanih sorbenata ustanovljeno je da se Fe-Mn binarni oksidi i magnetni materijali, karakterišu relativno velikim specifičnim  površinama  (109-300  m 2 /g)  i  zapreminama  mezopora (0,144-0,403  cm 3 /g).  Velika  specifična  površina  i  razvijena  mikroporozna struktura uočena je kod GAC-FeMn (996 m 2 /g; 0,394 cm 3 /g). U poređenju sa ostalim  sintetisanim  sorbentima,  Chit-FeMn  je  karakterisala  najmanja specifična  površina  i  zapremina  mezopora  (1,99  m 2 /g;  0,014  cm 3 /g).  XRD analiza  Fe-Mn  binarnih  oksida  ukazala  je  da  je  fazna  struktura  sintetisanih Fe-Mn  binarnih  oksida  slična  ferihidratu  dok  je  fazna  struktura  magnetnih materijala ukazala na prisustvo magemita. Ispitivanja kinetike sorpcionog procesa ukazala su da je mehanizam sorpcije As(III)  i  As(V)  na  sintetisanim  sorbentima  sloţena  kombinacija  površinske hemisorpcije,  koja  se  odvija  kroz  granični  sloj  čestica  sorbenata  i unutarčestične difuzije. Tome u prilog išli su i rezultati FTIR analize kojima je potvrđeno da se sorpcija arsena na sintetisanim sorbentima ostvaruje kroz interakcije hidroksilnih grupa gvožđa prisutnih na površini sorbenata i arsena. Dodatno, pokazano je da se za razliku od sorpcije As(V), sorpcija As(III) na sorbentima  koji  pored  oksida  gvožđa  sadrže  i  okside  mangana  (Fe-Mn binarni oksidi, Mag-FeMn, Mag-Mn,Chit-FeMn i GAC-FeMn) odvija u dva koraka. U prvom koraku As(III) se oksiduje do As(V), dok u drugom koraku, oksidovani  As(V)  mehanizmom  ligandne  izmene  formira  komplekse  na površini ovih sorbenata. Afiniteti sorpcije Fe-Mn binarnih oksida (na osnovu Kd vrednosti)  za As(III) opadali su u nizu Fe-Mn 3:1 > Fe-Mn 1:1 > Fe-Mn 6:1 > Fe-Mn 9:1 odnosno kod  As(V):  Fe-Mn  6:1  >  Fe-Mn  3:1  >  Fe-Mn  9:1  >  Fe-Mn  1:1.  Kod magnetnih kompozita,  najveća Kd vrednost za As(III) i As(V) ustanovljena je kod  Mag-FeMn.  Uopšteno,  Kd vrednosti  za  As(III),  kod  magnetnih kompozita,  opadale  su  u  nizu:  Mag-FeMn  >  Mag-Mn  >  Mag  >  Mag-Fe, Slično, afinitet sorbenata za As(V), opadao je na sledeći način: Mag-FeMn > Mag  >  Mag-Fe  >  Mag-Mn.  U  poređenju  sa  neimpregniranim,  Kd vrednosti bile su daleko veće kod obloţenih materijala, Chit-FeMn i GAC-FeMn, što je ukazalo  na  značajan  doprinos  Fe-Mn  binarnog  oksida  adsorpcionom kapacitetu neimpregniranih medija za As(III) i As(V). U  odnosu  na  ostale  ispitivane  anjone,  najveći  uticaj  na  sorpciju  oba  oblika arsena  na  svim  sintetisanim  sorbentima  uočen  je  kod  fosfata,  dok  je  uticaj nitrata i hlorida, u svim slučajevima bio bez značaja. Uticaj ispitivanih anjona na  sorpciju  As(III)  i  As(V)  na  Fe-Mn  binarnim  oksidima,  magnetnim materijalima, Chit-FeMn kao i na sorpciju As(V) na GAC-FeMn, opadao je u nizu: fosfati > silikati > karbonati > sulfati > nitrati > hloridi. Slično, uticaj ispitivanih  anjona  na  sorpciju  As(III)  na  GAC-FeMn  je  opadao  na  sledeći način: fosfati > silikati > sulfati > karbonati > nitrati > hloridi.Primenom  smeše  NaCl-NaOH-NaOCl  odnosno  primenom  0,1  M  i  0,5  M  rastvora NaOH, ustanovljeno je da se sintetisani sorbenti mogu jednostavno i  efikasno  regenerisati  i  višestruko  primeniti,  što  je  od  izuzetnog  značaja  sa ekološkog i ekonomskog aspekta.  Najmanje smanjenje sorpcionog kapaciteta  i za As(III) i za As(V), nakon pet ciklusa sorpcije -desorpcije, ustanovljeno je kod binarnog oksida sa Fe:Mn molskim odnosom 3:1 i Mag-FeMn.  Na osnovu rezultata prikazanih u ovom radu, može se zaključiti da sintetisani sorbenti,  Fe-Mn  binarni  oksidi  i  magnetni  kompoziti,  posebno  Mag-FeMn, mogu  biti  efikasna  i  ekonomična  alternativa  skupim  komercijalnim sorbentima  i  drugim  sofisticiranim  tehnologijama.  Visok  oksidacioni  i sorpcioni kapacitet ovih  materijala, koji obezbeđuje istovremeno uklanjanje  oba oksidaciona oblika arsena daje veliku prednost ovim sorbentima i čini ih veoma  atraktivnim  i  obećavajućim  u  tretmanu  voda.  Dodatni  benefit magnetnih  sorbenata,  pre  svega  Mag-FeMn,  ogleda  se  u  njegovoj jednostavnoj separaciji iz vodenog medijuma i recirkulaciji u sistemu. Glavne prednosti  sintetisanih  Chit-FeMn  i  GAC-FeMn,  ogledaju  se  u  mogućnosti  njihove primene kao efikasne filtracione ispune.The  presence  of  inorganic  arsenic  in  groundwater  used  for  drinking  water supply  is  a  global  problem.  Different  techniques  such  as  oxidation, coagulation,  adsorption,  ion  exchange,  and  membrane  filtration  have  been developed  and  applied  for  arsenic  removal  from  aqueous  media.  Among these  technologies,   adsorption  is  regarded  as  one  of  the  most  promising approaches to remove arsenic from water because of its high efficiency, low cost, simplicity of operation. Although many sorbents for arsenic removal are available on the market, there is still a need to identify and develop new  lowcost  sorbents which are highly effective in removing both oxidation states of arsenic, As(III) and As(V). This dissertation therefore presents the synthesis and  characterization  of  ten  new  iron  and  manganese  based  sorbents specifically developed for effective As removal. The Fe- Mn binary oxides were prepared with Fe:Mn molar ratios of 1:1, 3:1,6:1 and 9:1, while four heterogeneous magnetic composites (Mag, Mag-Fe,Mag-Mn,  Mag-FeMn)  were  synthesized  by  combining  the  heterogeneous nucleation  technique  with  precipitation.  The  remaining  two  materials, Chit-FeMn  and  GAC-FeMn,  were  created  by  modifying  the  Chitosan  and GAC  biopolymers  with  Fe-Mn  binary   oxide  (Chit-FeMn  and  GAC-FeMn).Multiple  techniques  were  applied  to  determine  the  physical  and  chemical characteristics  of  the  resulting  sorbents  (including  SEM/EDS,  XRD,  FTIR and BET analyses). In order to establish which sorbents show  the greatest promise for application during  drinking  water  treatment,  the  sorption  capacity  of  the  sorbents,  theAs(III)  and  As(V)  sorption  mechanisms,  and  the  impact  of  various  factors relevant to arsenic sorption, including the regeneration potential and the reuse potential of the sorbents, were all investigated in  batch experiments. During the physical characterisation, the Fe-Mn binary oxides and magnetic materials  were  found  to  have  relatively  large  specific  surface  areas (109-300 m 2 /g) and mesopore volumes (0.144-0.403 cm 3 /g).  A large specific surface  area  and  microporous  structure  was  observed  for  GAC-FeMn  (996 m 2 /g;  0.394  cm 3 /g).  In  comparison  with  the  other  synthesized  sorbents,  Chit-FeMn has the smallest specific surface area and pore volume (1.99 m 2 /g; 0.014  cm 3 /g).  XRD  analyses  of  the  Fe-Mn  binary  oxides  indicated  that  the phase  structure  of  the  synthesized  Fe-Mn  binary  oxides  was  similar  to ferrihydrate,  while  the  phase  structure  of  the  magnetic  materials  showed  a good agreement with the XRD diffractogram of maghemite. Investigations into As sorption process kinetics have shown that the sorption mechanism  for  both  As(III)  and  As(V)  on  the  synthesized  sorbents  is  a combination  of  surface  hemisorption,  which  takes  place  through  the boundary  layer  of  sorbent  particles,  and  intracellular  diffusion.  The  FTIR analyses  confirmed  that  arsenic  sorption  was  accomplished  through  the interactions  of  the  hydroxyl  groups  of  iron  present  on  the  surface  of  the sorbents and arsenic. In contrast to the sorption of As(V), it was also shown that  As(III)  sorption  onto  sorbents  containing  manganese  oxides  (Fe-Mn binary  oxides,  Mag-FeMn,  Mag-Mn,  Chit-FeMn  and  GAC  -FeMn)  takes place in two steps. In the first step As(III) is oxidized to As(V), while in the second  step,  the  oxidized  As(V)  forms  complexes  on  the  surface  of  the sorbents via ligand exchange. The  Fe-Mn  binary  oxide  sorption  capacities  (expressed  as  Kd values)  for As(III)   followed the trend Fe-Mn 3:1 > Fe-Mn 1:1 > Fe-Mn 6:1 > Fe-Mn 9:1, whereas the  As(V) trend was Fe-Mn 6:1 > Fe-Mn 3:1 > Fe-Mn 9:1 > Fe-Mn 1:1. In the magnetic  composites, the largest  Kd value for As(III) and As(V) was  obtained  for  Mag-FeMn.  Generally,  the  Kd values  for  As(III)  in  the magnetic composites decreased in the series: Mag-FeMn > Mag-Mn > Mag > Mag-Fe.  Similarly,  the  affinity  of  the  sorbents  for  As(V)  was  as  follows: Mag-FeMn  >  Mag  >  Mag-Fe  >  Mag- Mn.  In  comparison  to  the  nonimpregnated  materials,  the  Kd values  were  much  higher  for  the   boated materials,  Chit-FeMn  and  GAC-FeMn,  demonstrating  the  significant advantage  Fe-Mn  binary  oxides  provide  in  increasing  As(III)  and  As(V)  adsorption capacities. One  of  the  most  problematic  limiting  factors  in  applying  adsorption technologies during drinking water treatment is the presence of other water constituents which interfere with the adsorption process.  Investigations into the inhibitory effect of competive anions on the adsorption of both forms of arsenic  revealed  that  phosphates  were  the  worst  offenders  in  terms  ofreducing  the  arsenic  removal  efficacy  of  sorbents  investigated.  From  the largest  to  the  smallest  negative  influence  of  the  anions  investigated,  for As(III)  and  As(V)  adsorption  on  Fe-Mn  binary  oxides,  magnetic  materials and Chit-FeMn, as well as As(V) adsorption on GAC-FeMn, the order was: phosphates > silicates > carbonates > sulfates > nitrates > chlorides, with the presence  of  the  latter  two  anions  proving  almost  irrelevant  to  the  As adsorption  process.  Similarly,  the  negative  influence  of  anions  on  As(III) sorption on GAC-FeMn was: phosphates > silicates > sulphates > carbonates > nitrates > chlorides. Another  issue  with  applying  adsorption  in  real  treatment  conditions  is  the need to regularly  regenerate and/or replace the spent sorbent. In this work, a simple  and  efficient  process  for  sorbent   rfegeneration  is  demonstrated.  This regeneration  process  can  be  applied  to  the  sorbents  investigated  multiple times, and uses an NaCl-NaOH-NaOCl mixture, or 0.1 M and 0.5 M NaOH solutions.  This  finding  is  of  great  importance  from  an  ecological  and economic point of view. The minimum reduction in the sorption capacity for both As(III) and As(V), after five sorption-regeneration cycles, was found in  the  binary  oxide  with  a  3:1  Fe:Mn  molar  ratio  and  Mag-FeMn.  Arsenic sorption  behaviour  was  also  investigated  using  real  groundwater  samples, with the results demonstrating the great potential of 3:1 Fe-Mn binary oxide and Mag- FeMn. However, Chit-FeMn and GAC-FeMn were less effective at adsorbing As from the groundwater samples.Based on the results presented in this dissertation, it can  be concluded that the synthesized  sorbents,  especially  the  Fe-Mn  binary  oxides  and  magnetic composites,  and  Mag-FeMn  in  particular,  can  be  efficient  and  economical alternatives  to  expensive  commercial  sorbents  and  other  sophisticated  As removal  technologies.  The  high  oxidation  and  sorption  capacity   of  these materials,  which  ensure  the  simultaneous  removal  of  arsenic  with  both oxidation states, is a large advantage for these sorbents and makes them very attractive  and  promising  for  application  in  drinking  water  treatment.  An additional  benefit of the magnetic sorbents, primarily Mag-FeMn, is the ease with  which  they  may  be  separated  from  the  aqueous  medium,  allowing  for simple  recirculation within a system. Similarly,  the main advantages of  the synthesized Chit- FeMn and GAC-FeMn are reflected in their application as effective filtration media

Teratom jajnika u rutinskom bioptičkom materijalu u petogodišnjem razdoblju

Teratomas are tumors derived from germ cells, most frequently arising in the gonads. The aim of this study was to determine the number of ovarian teratomas diagnosed in the routine biopsy material at Ljudevit Jurak Clinical Department of Pathology, Sestre milosrdnice University Hospital Center during a 5-year period, as well as their clinical, gross and microscopic characteristics. Teratomas accounted for 48.6% (n=166) of primary ovarian tumors. The patient mean age was 34.74±12.37 years. Difference in the incidence of teratoma between the left and right ovary was not significant; bilateral teratoma was found in 13 patients. Teratomas were detected by ultrasonography in 115 (69.27%) cases and the rest were found during surgery performed for other indications. Most teratomas (n=161; 96.9%) were mature and cystic (dermoid cysts). Mature and solid teratomas were diagnosed in 5 (3.01%), ovarian struma in 2 (1.8%) cases and strumal carcinoid in 1 (1.2%) case. Mature cystic teratomas contained sebaceous material in 123 (76.8%) cases, and a total of 16 teeth were found; 157 (94.5%) teratomas measured <10 cm in largest diameter. Microscopically, mature cystic teratomas most frequently contained ectodermal (skin with appendages, mature glia and nerve ganglia) and mesodermal (fibrous, fat tissue, cartilage and bone) tissues. Frequently found tissues of endodermal origin were respiratory and intestinal epithelia. Small foci of thyroid tissue were found in 20 (12%) teratomas. Chronic granulomatous foreign body reaction in the wall of mature cystic teratomas was found in 11 (6.8%) tumors.Teratomi su tumori podrijetla zametnih stanica koji se najčešće razvijaju u gonadama. Cilj rada bio je utvrditi koliko je dijagnoza teratoma jajnika postavljeno na rutinskom bioptičkom materijalu Kliničkoga zavoda za patologiju „Ljudevit Jurak“ Kliničkoga bolničkog centra „Sestre milosrdnice“ u Zagrebu u petogodišnjem razdoblju, kao i koje su bile njihove kliničke, makroskopske i mikroskopske osobine. U analiziranom razdoblju teratomi su sačinjavali 166 (44,86%) primarnih tumora jajnika. Srednja dob bolesnica s teratomom jajnika bila je 35±12,37 godina. Nije pronađena statistički značajna razlika u učestalosti teratoma lijevog i desnog jajnika, a u 13 (7,8%) bolesnica teratom je bio obostran. Teratom je u 115 (69.3%) slučajeva otkriven ultrazvukom, u 21 (12,6%) je ultrazvukom postavljena dijagnoza nespecifi ciranog cističnog tumora, a u 16 (9,6%) slučajeva teratom je otkriven prilikom operacijskog zahvata učinjenog iz nekog drugog razloga. U 160 (96,4%) slučajeva radilo se o zrelim cističnim teratomima (dermoidnim cistama), od kojih je 123 (76,8%) bilo ispunjeno lojem i u kojima je pronađeno sveukupno 16 zuba. U 157 (94,6%) slučajeva najveći promjer teratoma iznosio je do 10 cm. Mikroskopski, zreli cistični teratomi najčešće su sadržavali tkiva ektodermalnog i mezodermalnog podrijetla i to u 154 (96,3%) slučaja kožu s kožnim adneksima, odnosno u 148 (92,54%) slučaja vezivo. Od drugih ektodermalnih tkiva po učestalosti su slijedili zrela glija i živčani gangliji, a od mezodermalnih tkiva zrelo masno tkivo, hrskavica i kost. Od tkiva endodermalnog podrijetla najčešće je pronađen respiracijski i crijevni epitel. Manja žarišta tkiva štitnjače pronađena su u 19 (12%) cističnih teratoma. U 11 (7%) cističnih teratoma u stijenci su pronađena žarišta kronične upale tipa stranog tijela. Solidne građe bilo je 5 (3%) teratoma, od čega u 3 (2%) slučaja struma jajnika, a u 2 (1%) slučaja strumalni karcinoid

Arsenic Removal from Water by Green Synthesized Magnetic Nanoparticles

Magnetite nanoparticles were synthesized by a simple and ecofriendly method using onion peel (MNp-OP) and corn silk extract (MNp-CS), in order to develop new low-cost adsorbents for arsenic removal from groundwater. As a point of comparison, magnetite nanoparticles were also synthesized with a conventional chemical process (MNp-CO). The antioxidant potential of onion peel and corn silk extracts was determined using ferric reducing antioxidant power (FRAP) and free radical (DPPH) scavenging assays, including the total phenolics, flavonoids and tannins contents. The synthesized magnetite nanoparticles were characterised using different techniques (Scanning electron microscope/Energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) surface area analyzer). The adsorption capacity of MNp-OP and MNp-CS and the arsenic removal mechanism of these novel adsorbents was investigated through kinetic and equilibrium experiments and their corresponding mathematical models. Characterisation of MNp-OP and MNp-CS shows high BET specific surface areas of 243 m2/g and 261 m2/g, respectively. XRD and FTIR analysis confirmed the formation and presence of magnetite nanoparticles. The arsenic adsorption mechanism on MNp-OP, MNp-CS and MNp-CO involves chemisorption, intraparticle and external diffusion. Maximal adsorption capacities of MNp-OP, MNp-CS and MNp-CO were 1.86, 2.79, and 1.30 mg/g respectively. The green synthesis applied using onion peel and corn silk extracts was cost effective and environmentally friendly, and results in adsorbents with a high capacity for arsenic and magnetic properties, making them a very promising alternative approach in the treatment of arsenic contaminated groundwater

Sorption Behavior of Organic Pollutants on Biodegradable and Nondegradable Microplastics: pH Effects

Microplastics (MPs), chlorinated phenols (CPs), polycyclic aromatic hydrocarbons (PAHs) and halogenated benzenes (HBs) are pollutants that are widely present in freshwater systems. As alternatives to conventional plastics, bioplastics are receiving a lot of attention, but there are limited data on their impact on pollutant behavior. This work therefore investigated the impact of pH on the sorption of CPs, PAHs and HBs, as some of the toxic and highly persistent pollutants, on seven different plastics using kinetic and isotherm studies. The pH of the water matrix impacted the adsorption behavior of CPs on all selected MPs, with the highest degree of adsorption occurring at pH 7 for the majority of the selected CPs. The highest adsorption affinity of CPs on the MPs, at pH 7, was obtained for 4-chlorophenol and 2,4-dichlorophenol on powdered polyethylene standard (qt = 221 μg/g), while the lowest was obtained for the adsorption of pentachlorophenol on polyethylene terephthalate (qt = 25 μg/g). On the other hand, the pH value of the water matrix did not affect the adsorption of halogenated benzenes and PAHs on MPs. The pseudo-second-order rate model fit the adsorption kinetics data of all experiments. The results obtained for the adsorption of CPs on MPs indicated a lower sorption affinity of CPs with MPs at pH 4 and pH 10 compared to pH 7. The Langmuir isotherm, at pH 7, implied that 4-chlorophenol’s adsorption affinity was not significantly influenced by the type of MPs. On the other hand, at pH 7, the adsorption of 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol varied greatly, with powdered MP types showing the highest affinity for CP adsorption. Furthermore, the obtained adsorption isotherm results imply that electrostatic attraction, hydrogen bonds, π-π interactions and van der Waals interactions, are an integral part of adsorption mechanisms of the CPs on the MPs

Impact of Microplastics on the Fate and Behaviour of Arsenic in the Environment and Their Significance for Drinking Water Supply

The ubiquitous presence of microplastics (MPs) is a topic of great concern. Not only do MPs themselves represent potential toxicants for human health, they are never found alone in the environment and interact with and adsorb a variety of toxicologically significant pollutants. This review summarises recent work on interactions between MPs and heavy metals in the environment, with a special focus on arsenic, one of the most widespread and problematic water contaminants. Evidence for the adsorption of arsenic onto MP surfaces is given and the recent research into the consequences of this phenomenon for freshwater, marine, and soil environments presented. Finally, the lack of research into the significance of interactions between arsenic and MPs during drinking water treatment is highlighted. The performance of arsenic removal technologies is governed by a multitude of different factors, and with MPs detected in water sources all over the world, data on how these MPs impact the removal of arsenic and, indeed, other major water contaminants are urgently needed

Photocatalytic Degradation of Magenta Effluent Using Magnetite Doped TiO2 in Solar Parabolic Trough Concentrator

Due to population growth and industrial development consumption of non-renewable energy sources, and consequently pollution, has increased. In order to reduce energy utilisation and preserve the environment, developed and developing countries are increasingly trying to find solutions based on renewable energy sources. Cost-effective wastewater treatment methods using solar energy would significantly ensure effective water source utilisation, thereby contributing towards sustainable development goals. In this paper, special emphasis is given to the use of solar energy as the driving force of the process, as well as the use of highly active magnetic TiO2-based catalysts. Therefore, in this study, we investigated the possibility of photocatalytic degradation of aqueous magenta graphic dye using titanium dioxide as a catalyst and DSD model in order to achieve the best process optimisation. TiO2 was successfully coated with magnetic nanoparticles by one step process and characterized using different techniques (BET, SEM/EDS, FTIR, XRD). Based on DSD statistical method optimal reaction conditions were pH = 6.5; dye concentration 100 mg/L; TiO2&ndash;Fe3O4 0.6 g/L, at which the highest degree of magenta dye decolourisation was achieved (85%). Application of solar energy coupled with magnetic TiO2 catalyst which could be recovered and reused makes this approach a promising alternative in green wastewater treatment

Photocatalytic Degradation of Magenta Effluent Using Magnetite Doped TiO₂ in Solar Parabolic Trough Concentrator

Due to population growth and industrial development consumption of non-renewable energy sources, and consequently pollution, has increased. In order to reduce energy utilisation and preserve the environment, developed and developing countries are increasingly trying to find solutions based on renewable energy sources. Cost-effective wastewater treatment methods using solar energy would significantly ensure effective water source utilisation, thereby contributing towards sustainable development goals. In this paper, special emphasis is given to the use of solar energy as the driving force of the process, as well as the use of highly active magnetic TiO2-based catalysts. Therefore, in this study, we investigated the possibility of photocatalytic degradation of aqueous magenta graphic dye using titanium dioxide as a catalyst and DSD model in order to achieve the best process optimisation. TiO2 was successfully coated with magnetic nanoparticles by one step process and characterized using different techniques (BET, SEM/EDS, FTIR, XRD). Based on DSD statistical method optimal reaction conditions were pH = 6.5; dye concentration 100 mg/L; TiO2–Fe3O4 0.6 g/L, at which the highest degree of magenta dye decolourisation was achieved (85%). Application of solar energy coupled with magnetic TiO2 catalyst which could be recovered and reused makes this approach a promising alternative in green wastewater treatment

Changing body structure components and motor skills in military high school students within one year

Background/Aim. Proper growth and development of adolescents in the morphological, functional and psychosocial aspects is the imperative of the educational process. The aim of this study was to determine the status and changes in the indicators of morphological characteristics, motor skills and lifestyle habits among the students of the Military High School in Belgrade. Methods. The study included 217 students aged 15 to 18 years (from the first to the fourth grade). The two measurements performed at the intervals of one year were used to determine: the body structure by means of 10 variables and motor skills by 4 variables, while life habits were determined by 25 variables. Results. The differences in the indicators of morphological characteristics were recorded in all the groups, being the highest in the first year of schooling. During the period of growing up, a reduction of fatty component in percentage values was found, as well as an increase of muscle mass. The progressive growth of motor skills in the first, second and the third grade was recorded in the manifestation of power, and endurance improved only in the first year. In terms of dietary habits, there was no difference among the groups. Conclusion. The obtained results indicate proper morphological and motor development and the formation of lifestyle habits. The data obtained will serve as a basis for health and functional prevention and upgrading in terms of improvement of the process of military education. [Projekat Ministarstva nauke Republike Srbije, br. III47015

Comparing the Adsorption Performance of Multiwalled Carbon Nanotubes Oxidized by Varying Degrees for Removal of Low Levels of Copper, Nickel and Chromium(VI) from Aqueous Solutions

Functionalized multiwalled carbon nanotubes (MWCNTs) have drawn wide attention in recent years as novel materials for the removal of heavy metals from the aquatic media. This paper investigates the effect that the functionalization (oxidation) process duration time (3 h or 6 h) has on the ability of MWCNTs to treat water contaminated with low levels of Cu(II), Ni(II) and Cr(VI) (initial concentrations 0.5–5 mg L−1) and elucidates the adsorption mechanisms involved. Adsorbent characterization showed that the molar ratio of C and O in these materials was slightly lower for the oxMWCNT6h, due to the higher degree of oxidation, but the specific surface areas and mesopore volumes of these materials were very similar, suggesting that prolonging the functionalization duration had an insignificant effect on the physical characteristics of oxidized multiwalled carbon nanotubes (oxMWCNTs). Increasing the pH of the solutions from pH 2 to pH 8 had a large positive impact on the removal of Cu(II) and Ni(II) by oxMWCNT, but reduced the adsorption of Cr(VI). However, the ionic strength of the solutions had far less pronounced effects. Coupled with the results of fitting the kinetics data to the Elowich and Weber–Morris models, we conclude that adsorption of Cu(II) and Ni(II) is largely driven by electrostatic interactions and surface complexation at the interface of the adsorbate/adsorbent system, whereas the slower adsorption of Cr(VI) on the oxMWCNTs investigated is controlled by an additional chemisorption step where Cr(VI) is reduced to Cr(III). Both oxMWCNT3h and oxMWCNT6h have high adsorption affinities for the heavy metals investigated, with adsorption capacities (expressed by the Freundlich coefficient KF) ranging from 1.24 to 13.2 (mg g−1)/(mg l−1)n, highlighting the great potential such adsorbents have in the removal of heavy metals from aqueous solutions