Increasing concern about the pollution of environment by inorganic and organic chemicals arising from naturally occurring ecological events and industrial processes has created a need for the search of new techniques in the removal of these contaminants. One of the natural material that can be used in such processes is clay. Clay minerals have large surface areas and high cation exchange capacities which enables them to be modified by cationic surfactants. The material prepared, often called as &amp / #8216 / organoclay&amp / #8217 / , can be used to remove hydrophobic organic and anionic contaminants from polluted water. Among the anionic contaminants, oxyanions such as nitrate, chromate are detrimental to human life and environment even at &micro / g/L- mg/L levels. Application of organoclays for their removal from polluted water appears as one of the practical and rather cheap solution. In this study, a local clay from Ankara-Kalecik (Han&ccedil / ili Bentonite) was modified by hexadecyltrimethylammonium bromide (HDTMA-Br) to a level of twice of its cation exchange capacity. This process alters the negatively charged surface of the clay into a positively charged one, providing sites for the removal of anionic contaminants. In this study, the degree of HDTMA+ uptake by the clay within a period of eight hours is found to be 97% of the initial amount added. In desorption studies it was revealed that only about 1% of the sorbed HTDMA+ was leached in a seven days of water-organoclay interaction revealing a rather stable organoclay structure in aqeous media. Sorption experiments with nitrate, borate, and chromate solutions were performed in order to determine the anion sorption capacity of the organoclays prepared. It turns out that while untreated clay has insignificant capacity, the modified clay can remove considerable amount of nitrate and chromate ions from aqeous solutions. While the nitrate sorption was increased about eleven fold, change in chromate sorption was reached to a level of twenty fold compared to that of the untreated clay. Sorption data for nitrate and chromate are both well described by the Langmuir isotherms. No significant change was observed in case of borate-organoclay interaction. Desorption of nitrate and chromate ions from organoclay surface were also investigated. Sorption of these oxyanions were found to be almost irreversible in aqeous media. The results imply that a properly prepared organoclay can be used for the removal of oxyanions, such as nitrate and chromate from polluted water systems.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-06-26T11:43:08Z No. of bitstreams: 1 UÉDSON ALEXANDRE DO NASCIMENTO - TESE (PPGCEMat) 2016.pdf: 2537041 bytes, checksum: 43e8f4d37a08e791d0323dc0ce915cb4 (MD5) / Made available in DSpace on 2018-06-26T11:43:08Z (GMT). No. of bitstreams: 1 UÉDSON ALEXANDRE DO NASCIMENTO - TESE (PPGCEMat) 2016.pdf: 2537041 bytes, checksum: 43e8f4d37a08e791d0323dc0ce915cb4 (MD5) Previous issue date: 2016-02-26 / Neste trabalho, blendas de polietileno de alta densidade com polietileno linear de baixa densidade metalocênico, PEAD/m-PELBD, foram preparadas empregando uma extrusora dupla rosca, cônica, contrarotacional interpenetrante e os efeitos do tipo e do teor do m-PELBD nas propriedades de impacto e de tração foram estudados. A blenda PEAD/m-PELBD com melhor relação de propriedades, tenacidade/rigidez, foi modificada com argila montmorilonita organofílica comercial Cloisite 20A, nos teores de 1, 3, 5 e 10 pcr, visando à obtenção de um híbrido com propriedades comparáveis, particularmente, em processamento e tenacidade/rigidez, às da resina de PEAD importada, PEAD Dowlex IP–10262, utilizada para fabricação de embalagens injetadas para o envase e transporte de produtos químicos perigosos. De acordo com os resultados da caracterização mecânica (impacto e tração), ficou evidenciado que o tipo e o teor de m-PELBD influenciaram nestas propriedades. Dentre os m-PELBDs estudados, Flexus 7200 e Flexus 9200, o Flexus 7200 resultou na melhor relação de propriedades e dentre os teores avaliados (10, 17 e 25%), o teor de 17% foi mais efetivo. A blenda PEAD/17% m-PELBD, blenda 7217, apresentou resistência à tração no escoamento comparável a da resina importada; resistência ao impacto 57,7% superior e módulo elástico 23,6% inferior. Como a rigidez da blenda 7217 foi inferior à da resina importada, a mesma foi modificada com a argila Cloisite 20A. De acordo com os dados de difratometria de raios X (DRX), a incorporação da argila à blenda 7217, em todos os teores estudados, não resultou na formação de nanocompósitos. Apesar disso, as propriedades de cristalinidade (determinada por calorimetria exploratória diferencial – DSC) e de estabilidade térmica (determinada por termogravimetria - TGA) da blenda 7217 modificada com 10 pcr de argila (7217AO-10), foram superiores as da blenda pura. A resistência à tração foi mantida, a resistência ao impacto diminuiu e o módulo elástico aumentou, em relação a blenda pura. Em comparação com a resina importada, a resistência à tração do híbrido 7217AO-10 foi 8% superior, a resistência ao impacto foi 12% inferior e o módulo elástico 7% inferior. De forma geral, a blenda 7217, modificada com 10 pcr de argila, apresentou processabilidade e propriedades mecânicas comparáveis as da resina importada (PEAD Dowlex IP–10262). / Blends of high density polyethylene with metallocene linear low density polyethylene, HDPE/m-LLDPE, were prepared by melt compounding in a twin-screw extruder. The m-LLDPE type and content effects on impact and tensile properties were studied. According to the results, these parameters influenced the properties of m-LLDPE. The blend prepared with m-LLDPE Flexus 7200 with the 17% concentration (7217 blend) showed the best properties. However, their hardness was lower than the HDPE Dowlex IP-10262 resin, used for dangerous chemicals transport containers manufacture. The 7217 blend was modified with organophilic montmorillonite (Cloisite 20A organoclay). The diffraction X-ray data (XRD) showed that the 7217 blend modification, with organoclay, on all studied concentrations, did not result in nanocomposites. Nevertheless, the crystallinity properties (determined by differential scanning calorimetry – DSC) and thermal stability (determined by thermogravimetric analysis – TGA) of the 7217 blend, modified with 10 phr of organoclay (7217AO-10) were higher than the pure blend. In addition, the modified blend showed decreased impact resistance, increased elastic modulus and the same tensile strength. As compared to Dowlex IP-10262 HDPE, the tensile strength of 7217AO-10 hybrid was 8% higher, the impact strength was 12% lower and the elastic modulus was 7% lower. In general, the processability and mechanical properties of 7217 blend, modified with 10phr of Cloisite 20A, were similar to that HDPE Dowlex IP-10262. Therefore, this hybrid has great use potencial for dangerous chemicals transport containers manufacture, replacing the HDPE Dowlex IP-10262 resin.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nanocompósitos de poliamida 6 (PA6) e montmorilonita modificada com sal de amônio quaternário têm sido estudados, visando melhorar as propriedades térmicas e mecânicas. De fato os efeitos da nano-escala e da interação carga-matriz resultam em maior módulo de elasticidade e resistência à tração, porém a deformação é reduzida. Assim, nesse trabalho, optou-se por adicionar elastômeros, terpolímero de etileno-propileno-dieno (EPDM) e terpolímero de etileno-propileno-dieno modificado com anidrido maleico (EPDM-MA), ao sistema PA 6/argila organofílica para recuperar os valores de deformação. Foi utilizada montmorilonita modificada com cloreto de dimetildioctadecil amônio. A intercalação por fusão foi realizada em câmara interna de mistura. Além das propriedades mecânicas, térmicas e reológicas, foram investigadas as modificações na cristalinidade da fase PA-6 em função da adição da argila modificada, EPDM e EPDM-MA, detectando-se as variações no grau de cristalinidade e nas temperaturas de fusão e cristalização. Os difratogramas de raios-x revelaram ocorrência de intercalação/esfoliação e também modificação da forma cristalina da PA 6, indicando a formação do cristal gama / Nanocomposites of polyamide 6 and montmorillonite modified with alquil-ammonium salts have been studied, searching for the improvement of mechanical and thermal properties. In fact the effects of the nano-scale and the interaction matrix-filler result in larger module of elasticity and tensile strength. However, the elongation at break was greatly reduced. Therefore, in this work, it has been decided to add elastomers, ethylene-proplene-diene terpolymer (EPDM) and ethylene-proplene-diene terpolymer funcionalized with maleic anhydride (EPDM-MA), to the system PA6/organoclay, using modified montmorillonite with ditallowdimethylammonium chloride. The nanocomposites were prepared by melt intercalation technique in a mix internal chamber. Besides the mechanical, thermal and rheological properties, the modifications in the crystallinity of PA6 phase were investigated, being detected the variations in the degree of crystallinity and in the melt temperature and crystallization. The diffractograms of x-ray (XRD) revealed occurrence of intercalation/exfoliation as well as modification of the crystalline form of PA 6, indicating the formation of  crystals

Orientador: Melissa Gurgel Adeodato Vieira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-24T22:58:23Z (GMT). No. of bitstreams: 1 Stofela_SaraKarolineFigueiredo_M.pdf: 3437110 bytes, checksum: 75c3b9d81bd674bc6b2d46a4347ba152 (MD5) Previous issue date: 2014 / Resumo: Resíduos contaminados com compostos orgânicos, sendo grande parte formados por hidrocarbonetos aromáticos, como o benzeno, tolueno e xileno, vem sendo gerados em grandes quantidades nas indústrias e em derramamentos de postos de estocagem de combustíveis. Sendo assim, surge espaço para novas pesquisas de tratamento desses efluentes, como a adsorção em argilas organofílicas. Portanto, o objetivo deste trabalho é avaliar o potencial da argila organofílica Spectrogel na adsorção dos compostos BTX. Para este estudo foram realizados teste de hidratação e expansão em meio orgânico, estudo do efeito do pH, avaliação do potencial de remoção e estudo cinético, por meio de ensaios cinéticos de adsorção monocomposto, bicompostos e tricompostos, estudo de equilíbrio, atráves de ensaios de equilíbrio monocomposto, bicompostos e tricompostos, nas temperaturas de 15, 25 e 35 oC, estudo termodinâmico, caracterização do material adsorvente antes e após os ensaios de adsorção, estudo de regeneração do adsorvente, e análise estatística do processo de adsorção. A argila apresentou uma eficiência de remoção de 95%, 89% e 96% para o benzeno, tolueno e xileno, respectivamente e mostrou que o processo é rápido com no máximo 120 min para atingir o equilíbrio. No estudo cinético, tanto o modelo pseudoprimeira-ordem, quanto o pseudossegunda ordem apresentaram boas correlações. O modelo de difusão intrapartícula e modelo de Boyd indicaram que a adsorção é controlada tanto pela difusão intrapartícula, como pela difusão externa. O estudo de equilíbrio indicou que o xileno é o contaminante com maior afinidade pelo meios adsorvente. Entre os modelos de isotermas utilizados nos ajustes dos dados experimentais, o modelo de Dubinin-Radushkevitch foi o que apresentou melhor correlação para todas as isotermas monocomposto. Para as isotermas bicompostos, o modelo de Freundlich foi o que melhor se ajustou. Os parâmetros termodinâmicos mostraram que o processo de adsorção de BTX em argila Spectrogel é espontâneo e endotérmico. A caracterização do adsorvente após a adsorção dos BTX mostrou que o mesmo é pouco poroso e possui a superfície heterogênea, evidenciando a presença dos compostos BTX e algumas mudanças estruturais no material adsorvente. Por fim, os ensaios de regeneração indicaram a regeneração do adsorvente por meio do eluente etanol / Abstract: Contaminated waste with organic compounds, being largely composed of aromatic hydrocarbons such as benzene, toluene and xylene, has being generated in large quantities in industries and spills fuel storage stations. Thus, it arises space for further research about treatment of these effluents, such as adsorption on organoclay. Therefore, the aim of this study is to evaluate the adsorption of BTX compounds into organoclay Spectrogel. For this study tests of hydration and expansion in organic media and tests of the effect of pH were conducted. Equilibrium study was also performed by tests of mono-component, bi-component and multicomponent solutions at temperatures of 15, 25 and 35 oC. The adsorbent was characterized before and after the adsorption experiments. Finally, the regeneration of the adsorbent through eluents and a statistical study of the adsorption process were also performed. The evaluation of the potential removal provided a removal efficiency of 95%, 89% and 96% for benzene, toluene and xylene, respectively and showed that the process is fast taking a maximum of 120 min to reach equilibrium. In the kinetic study, both the pseudo first order model, as well as pseudo second order model showed a good correlation. The intraparticle diffusion model and Boyd model indicated that adsorption is controlled by both intraparticle diffusion and external diffusion. The equilibrium study indicated that xylene is the most competitive contaminant by active adsorption site. Among the isotherm models used, only the Dubinin-Radushkevitch showed a good correlation for all mono-component isotherms. For bi-component isotherms, the Freundlich model showed the best fit. The thermodynamic parameters indicated that the adsorption process of BTX into clay is spontaneous and endothermic. The characterization of the study showed that the this adsorbent is porous and presents a heterogeneous surface after adsorption and the presence of BTX compounds and structural changes were observed in the adsorbent material after process. The dessorption tests indicated a possible regeneration of the adsorbent using ethanol as eluent.z / Mestrado / Desenvolvimento de Processos Químicos / Mestra em Engenharia Química

<p>Fokus ove doktorske disertacije je bilo izučavanje sorpcionog pona&scaron;anja tri herbicida koji se nalaze na listi prioritetnih supstanci prema Okvirnoj Direktivi o vodama EU (2000/60/EC) sa generalnim ciljem dobijanja podataka korisnih za prioritizaciju na osnovu novog fundamentalnog znanja o efikasnosti (ad)sorpcije za uklanjanje ovih<br />supstanci iz&nbsp; vode u lokalno specifičnim uslovima. Odabrani su ksenobiotici različite rastvorljivosti, hidrofobnosti i donorsko-akceptorskih osobina, koji&nbsp; pripadaju&nbsp; različitim klasama&nbsp; herbicida (dinitroanilinski-trifluralin, hloroacetamidni-alahlor i triazinski-&nbsp; atrazin). Prva faza je obuhvatala karakterizaciju sorbenata i vodenih matriksa .U sintetičkom matriksu, trifluralin pokazuje veći afinitet na ispitivanim sedimentima u odnosu na alahlor i atrazin. I u slučaju organoglina, sorpcija je najizraženija za trifluralin. Alahlor i atrazin pokazuju slične sorpcione kapacitete na TMA-K, dok je na TMA-B, sorpcija izraženija za alahlor u odnosu na atrazin. U&nbsp; zavisnosti od prirodnog matriksa, na oba sedimenta, najveće&nbsp; Kd vrednosti su dobijene za trifluralin, dok su Kd vrednosti za atrazin i alahlor&nbsp; bile veoma slične ili&nbsp;pak veće za atrazin. U slučaju organoglina, vrednosti&nbsp; K_d su rasle sa porastom log&nbsp; K_OW vrednosti herbicida na TMA-K u oba prirodna matriksa. Kada je u pitanju TMA-B, rast K_dvrednosti sa rastom log&nbsp; K_OW vrednosti uočava se u povr&scaron;inskom matriksu pri C_e&nbsp; = 0,05 mg/l i 0,5 mg/l, i podzemnom matriksu pri najvećoj ravnotežnoj koncentraciji C_e&nbsp; = 0,5 mg/l. Kao najefikasniji sorbenti su se pokazali&nbsp; TMA-B&nbsp;(Kd&nbsp; = 10,5 -&nbsp; 483 l/kg) i model sediment (Kd = 16,4 -&nbsp; 761 l/kg). Odsustvo jasne linearne korelacije izmeĎu&nbsp; Kd i&nbsp; % TOC upućuje na važnost interakcija mineralne faze i herbicida. U slučaju sedimenata nisu utvrđene korelacije K_d sa log&nbsp; K_OW&nbsp;vrednostima, dok kod organoglina one postoje. K<span id="cke_bm_184S" style="display: none;">&nbsp;</span>_d<span id="cke_bm_184E" style="display: none;">&nbsp;</span> /K_OW odnosi su najveći kod atrazina na svim sorbenti<span id="cke_bm_185E" style="display: none;">&nbsp;</span>ma pa se pretpostavlja da on najvi&scaron;e učestvuje u&nbsp; uspostavljanju specifičnih interakcija zbog svojih donorsko-akceptorskih osobina. &Scaron;to se tiče uticaja DOC,&nbsp; zaključuje se da poreĎenje efikasnosti sorbenata treba sprovoditi u prirodnim matriksima jer sorpcioni koeficijenti variraju u zavisnosti od&nbsp;koncentracije polutanata, tipa i sadržaja DOC. Kolonskim eksperimentima je pokazano da atrazin i alahlor prolaze kroz kolonu sedimenta, dok je trifluralin skoro u potpunosti adsorbovan i u vrlo maloj koncentraciji detektovan u efluentu &scaron;to je u saglasnosti sa rezultatima &scaron;aržnih eksperimenata na ovom sorbentu. Procenjeni faktor retardacije pomoću modela TransMod za atrazin je veći u prirodnim matriksima (R <span id="cke_bm_190S" style="display: none;">&nbsp;</span>_d<span id="cke_bm_190E" style="display: none;">&nbsp;</span> = 54 i R_d = 55 u podzemnoj i povr&scaron;inskoj vodi, redom) nego u sintetičkoj&nbsp;vodi (R_d = 40). Kod alahlora nisu uočene značajne promene faktora retardacije meĎu matriksima (R_d = 30-35). Ovi rezultati su suprotni očekivanjima na osnovu hidrofilnosti ksenobiotika i mogu biti&nbsp; rezultat upravo interakcija sa organskim materijama koje su bile izražene u kolonskim testovima, verovatno i vi&scaron;e nego u &scaron;aržnim testovima gde se nije pojavilo povećanje R_d vrednosti u prirodnim matriksima u odnosu na sintetički matriks.&nbsp; Bez obzira &scaron;to je&nbsp; alahlor hidrofobniji od atrazina, u uslovima datog matriksa i sorbenta ispoljava slične (&scaron;aržni testovi) ili<br />slabije sorpcione karakteristike&nbsp; (kolonski testovi)&nbsp; koje upućuju na mobilnost kroz prvi za&scaron;titini sloj.&nbsp; Treća faza je obuhvatala ispitivanje adsorpcije herbicida na aktivnim ugljevima u prahu. Ispitana je kinetika adsorpcionog procesa određivanjem koeficijenta za unutarčestični prenos mase herbicida u sirovim i ozoniranim prirodnim matriksima. Određena je efikasnost uklanjanja herbicida na razlilčitim ugljevima u prahu. Efikasnost uklanjanja se kretala u različitim opsezima u zavisnosti od odabranog uglja, vodenog matriksa i doze uglja. Na komercijalnim ugljevima najveća postignuta efikasnost (doza uglja od 15 mg/l) za&nbsp; alahlor iznosi u povr&scaron;inskoj vodi 95%, a u podzemnoj 76%. Za atrazin to je u povr&scaron;inskoj vodi 58% i u podzemoj vodi 56%, a za trifluralin u povr&scaron;inskoj vodi 87%, a u podzemnom matriksu 92%. Na uglju sitnih čestica koji se koristi u kombinaciji sa membranskom filtracijom ove<br />vrednosti su&nbsp; i veće. Stepen uklanjanja DOC na komercijalnim ugljevima (pri dozi od 15 mg/l) iznosi do 57% za povr&scaron;inski matriks i do&nbsp; 51% za podzemni matriks. Slična efikasnost u uklanjanju DOC je postignuta i na uglju sitnih čestica u oba matriksa. Ozonizacija je ispoljila očekivan negativan uticaj, vi&scaron;e ili manje izražen. U slučaju ksenobiotika, uticaji ozonizacije su bili različiti, u zavisnosti od primenjenog uglja, matriksa i supstance. Najizraženiji uticaj je kod alahlora,&nbsp; i to u negativnom smislu,<br />zbog pada efikasnosti uklanjanja, verovatno zbog kompeticije sa organskom materijom ili efekta solubilizacije. U nekim slučajevima, ali mnogo manje, taj efekat je primećen i kod trifluralina. Na oba komercijalna uglja primećen je pozitivan uticaj ozonizacije na uklanjanje atrazina, ali u različitim matriksima,&nbsp; pa se može spekulisati<br />pretpostavljanjem da dolazi do favorizovane raspodele u novim oblogama&nbsp; POM na uglju formiranim nakon ozonizacije koje su i dovoljno adsorbabilne, ali i sa dovoljno reaktivnim osobinama za asociranje sa polarnim supstancama, &scaron;to je delimično i potvrđeno rezultatima adsorpcione analize.&nbsp;&nbsp;</p> / <p>The focus of&nbsp; this doctoral thesis was the study of the sorption behavior of three herbicides which are on the list of priority substances according to Water Framework Directive (2000/60/EC). The aim&nbsp; was&nbsp; to obtain the&nbsp; data useful for prioritization on the basis of the&nbsp; new fundamental knowledge about (ad) sorption efficiency&nbsp; for the removal of these substances from the&nbsp; locally specific water matrices. Selected xenobiotics&nbsp; were&nbsp; differing&nbsp; in&nbsp; solubility, hydrophobicity, and donor-acceptor properties, which belong to different classes of compounds(trifluralin as herbicide, alachlor as chloracetamide herbicide and atrazine as triazine herbicide).&nbsp; In the first phase&nbsp; of the thesis&nbsp; characterization&nbsp; of sorbents and water matrices&nbsp; was performed. The aim of the second phase was the testing&nbsp; of&nbsp; the sorption and<br />desorption of organic xenobiotics in the sediments and organoclays. The equilibrium&nbsp; sorption parameters and removal efficiencies of herbicides were determined in different water matrices.&nbsp; In the synthetic matrix, trifluralin showed a higher sorption affinity onto tested sediments in comparison to the alachlor and atrazine. In the case of organoclays, sorption was mostly&nbsp; pronounced for trifluralin. Alachlor and atrazine have similar sorption capacities onto the TMA-K. For the TMA-B, the sorption was more pronounced for alachlor than atrazine. Depending on the natural water matrices,&nbsp; the highest&nbsp; K_d values were obtained for trifluralin onto both sediments. The&nbsp; K_d values for atrazine and alachlor were very similar or even greater for atrazine. In the case of organoclays, K_d values increased with increasing log&nbsp; K_OW values of herbicides onto TMA-K in both natural matrices. When it comes to TMA-B,&nbsp; K_d&nbsp; valuesincreased with increasing log&nbsp; K_OW values in&nbsp; the surface matrix for<br />C_e = 0,05 mg/l and 0,5 mg/l, and in groundwater at the highest equilibrium&nbsp; concentration&nbsp; C<span id="cke_bm_506S" style="display: none;">&nbsp;</span>_e<span id="cke_bm_506E" style="display: none;">&nbsp;</span>&nbsp; = 0,5 mg/l. TMA-B (K_d = 10,5&nbsp; -&nbsp; 483 l/kg) and model&nbsp; sediment&nbsp; (kd= 16,4 to 761 l/kg) were the most efficient s<span id="cke_bm_507E" style="display: none;">&nbsp;</span>orbents. The absence of&nbsp; the&nbsp; clear linear correlation between&nbsp; K_d and % TOC&nbsp; indicates the importance of the interaction of mineral phases and herbicides. Correlation between K<span id="cke_bm_513S" style="display: none;">&nbsp;</span>_d<span id="cke_bm_513E" style="display: none;">&nbsp;</span> and K_OW values did not existed in the case of sediments,&nbsp; contrary to the organoclays.&nbsp; Since K<span id="cke_bm_519S" style="display: none;">&nbsp;</span>_d<span id="cke_bm_519E" style="display: none;">&nbsp;</span> /K_oW ratios were the h<span id="cke_bm_520E" style="display: none;">&nbsp;</span><span id="cke_bm_514E" style="display: none;">&nbsp;</span>ighest for atrazine onto all sorbents, it&nbsp; was&nbsp; assumed that atrazine mostly participate in specific interactions due to its donor-acceptor properties. Regarding the&nbsp; influence of DOC on sorption, it was concluded that a comparison of sorbents efficiencies should be carried in&nbsp; native matrices as sorption coefficients vary depending on the concentration of pollutants, the type and content of DOC. Column&nbsp; experiments showed that atrazine and alachlor passed through the column of the sediment, while the trifluralin almost completely was adsorbed and in very low concentrations detected in the effluent which is in accordance with the results of the&nbsp; batch experiments.&nbsp; Estimated retardation factors of atrazine were higher in natural matrices (R<span id="cke_bm_525S" style="display: none;">&nbsp;</span>_d<span id="cke_bm_525E" style="display: none;">&nbsp;</span>= 54 and R_d = 55 in groundwater and surface water, respectively) than in&nbsp; the synthetic water (R_d= 40_{). I}n the case of alachlor, retardation factors were similar among water matrices (R_d = 30-35). These results are in the opposition&nbsp; based on the xenobiotic hydrophilicity, and they could be the consequence of interaction with the organic matter&nbsp; present&nbsp; in the column tests, probably more than in the batch tests. Estimations of&nbsp; R_d based on batch tests&nbsp; did not show an increase of R_d values in natural matrices, in comparison to the synthetic matrix. More hydrophobic alachlor, in the circumstances of the sorbent matrix exerts similar&nbsp; (batch&nbsp; tests) or lower sorption (column tests) characteristics that indicate mobility through the first protective layer.<span id="cke_bm_526E" style="display: none;">&nbsp;</span> The third phase&nbsp; included herbicide adsorption tests onto powdered activated carbons. The adsorption kinetics was examined by determining the intraparticle mass transfer coefficients for herbicides in raw and ozonated natural water matrices. The removal efficiencies of herbicides for different powdered activated carbons were determined. Removal efficiencies were in different ranges depending on the selected carbon, water matrix and carbon dose. The highest removal efficiencies&nbsp; for commercial carbons (for carbon dose of 15&nbsp; mg/l)&nbsp; for&nbsp; alachlor were 95% and 76% in surface and groundwater, respectively. The highest&nbsp; removal of atrazine was&nbsp; 58% in surface water and 56% in groundwater. In thecase of trifluralin, removal efficiencies were&nbsp; 87% in surface water and 92% in groundwater. The removal efficiencies for the carbon with fine particles&nbsp; (usually&nbsp; used in combination with a membrane filtration)&nbsp; were greater. The removal of DOC&nbsp; &nbsp; by&nbsp; commercial carbons (at the dose of 15 mg/l) was less than 57% in the surface water and 47% in groundwater. A similar efficiency in DOC removal was achieved for the carbon with fine particles in both water matrices. Ozonation showed the expected &nbsp; negative influence on&nbsp; DOC&nbsp; removal efficiencies, more or less pronounced. In the case of xenobiotics, ozonation influence was different, depending on the applied carbon and xenobiotic. The most important negative influence was&nbsp; in the case of alachlor probably due to competition with organic matter or solubilization effect. The&nbsp; same, but less pronounced effect was observed for trifluralin. The positive influence of ozonation was observed in removal of atrazine&nbsp; by&nbsp; both commercial carbons but in &nbsp; different water matrices.&nbsp; One can speculate that it comes to the favorable distribution in new NOM coatings on carbons formed upon ozonation, which are sufficiently adsorbable, but with enough reactive qualities for association with polar substances, which is partly confirmed by the results of adsorption analysis.</p>

The objective of this work was the development of an efficient adsorbent for irreversible immobilization of heavy metals in contaminated soils. The adsorbent was prepared by pillaring montmorillonite with silica followed by the grafting of a chelate ligand onto its surface. Its structure was studied by the Brunauer, Emmett, and Teller Method adsorption of N2, Dynamic Light Scattering, and Scanning Electron Microscopy. The adsorption capacity of the organoclay was measured by its mixing with contaminated kaolin soil samples and by analysis of heavy metal contents in leachate. The adsorbent was efficient in immobilization of heavy metals in both neutral aqueous and acidic media. In addition, the adsorbent was efficient in environmental samples reducing the concentration of iron in all samples in aqueous and acidic media. As a result, the adsorbent can be used for reduction of heavy metal leaching from contaminated sites.

Presence of a chelating ligand in the clay structure significantly improves its ability to immobilize heavy metals from contaminated sludge or wastewater. Two-step modification procedure comprising sequential pillaring and grafting of chelating agent to the modified clay is involved. Montmorillonite and kaolin were chosen as typical examples of expandable and non-expandable clays, correspondingly. Modifications with silica and ferric oxide were targeted on development of mesoporous structure. Laboratory tests of the organoclay efficiency for purification of wastewater were conducted with the most promising sample, i.e. organoclay with the highest specific loading of chelating agent. Experiments were conducted with model wastewater containing either individual or mixed cations of heavy metals. The modified organoclay displayed a high adsorption capacity on heavy metal cations even in acidic media. The method of modification presented in this work can be used for synthesis of efficient adsorbents for applications in contaminated areas.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho foram preparados nanocompósitos de elastômeros termoplásticos à base de PP/EPDM/argila organofílica. Foram utilizados como agentes interfaciais polipropileno e terpolímero de etileno-propileno-dieno ambos modificados com grupos anidrido maleico, PP-MA e EPDM-MA, respectivamente. Dois tipos de argila organofílica, que se diferenciam pela estrutura química do surfactante e conseqüentemente pela estabilidade térmica, foram empregados como carga inorgânica. Os nanocompósitos foram preparados pela técnica de intercalação por fusão em câmara interna de mistura e a incorporação da argila foi feita pela adição de masterbatches previamente preparados. Foram investigadas as propriedades de tração, reométricas e ainda a morfologia (cristalinidade e estrutura obtida) dos nanocompósitos a fim de estabelecer a influência do tipo e quantidade de argila organofílica e agente interfacial. Os resultados mostraram que a adição de agente interfacial melhorou a dispersão da argila organofílica na matriz de PP/EPDM, particularmente o PP-MA. Foram obtidos nanocompósitos com estruturas mistas intercaladas e esfoliadas, que resultaram em maiores valores de módulo de elasticidade e manutenção dos valores de deformação. As propriedades reométricas confirmaram o maior grau de dispersão da argila organofílica em nanocompósitos contendo PP-MA. Teores crescentes de argila reduziram a cristalinidade dos nanocompósitos, os quais quando reprocessados, mantiveram as características inerentes ao TPE de origem. Por fim, a estrutura do surfactante presente / In this work it was prepared nanocomposites based in PP/EPDM thermoplastic elastomer and organoclay. Maleinized polypropylene and ethylene-propylene-diene rubber, PP-MA and EPDM-MA, respectively, were employed as interfacial agents. Also two kinds of organoclays, differing about surfactant chemical structure and as consequence thermal stability, were investigated as inorganic filler. Nanocomposites were prepared by melt intercalation in an internal chamber mix and organoclay was incorporated by masterbatches addition, which ones were previously made. It was investigated the influence of amount and kind of organoclay and interfacial agent on tensile properties, rheology and morphology (crystallinity and structure type) of nanocomposites obtained. The results showed that interfacial agents addition promoted a better dispersion degree of organoclay platelets in PP/EPDM matrix, mainly PP-MA. Nanocomposites with both intercalated and exfoliated structures were obtained. These exhibited higher Young modulus and kept their elongation values. The better dispersion degree of clay platelets in nanocomposites containing PP-MA was confirmed by rheology measurements. Increasing amounts of organoclay lowered the crystallinity degree of nanocomposites but the reprocessability was maintained similar to that of pure TPE. Finally, the chemical structure of surfactants did not change the intercalation/exfoliation process due to the similarity of organoclay basal spacing and moderated TPE processing temperature.

Clay minerals have historically played a consequential role in human health. While the beginnings were rooted in geophagy, a primitive act of consuming earth, the health-related uses of clay minerals have evolved and diversified over time. As excipients in pharmaceutical formulations, clay minerals can attribute novel properties onto intercalated compounds. Intercalating oxybenzone, a UV filter, within the interlamellar space of montmorillonite is desirable in order to minimize direct contact with skin. Intercalating resveratrol, a compound known for attributing beneficial effects onto human health, may be advantageous since this compound is susceptible to cis-trans isomerisation. The strategy of using alkylammonium–modified clay was undertaken and proved successful for the intercalation of oxybenzone. The field of biopolymer/layered silicate nanocomposites is heavily researched for use in a multitude of applications. Novel montmorillonite nanocomposites were prepared with neutral guar gum and cationic guar gum, using an environmentally friendly process and are fully characterized.