Catalyst performance is a relevant factor in biodiesel production because it can affect the efficiency of the process. This work provides a study of the performance of heterogeneous catalysts for biodiesel production derived from thermal-treated hydrocalumite-type compounds. This work aimed to synthesize and characterize hydrocalumite-type compounds intercalated with chloride and nitrate, evaluate the effect of thermal treatments at different temperatures (500, 600, and 750 °C) on these materials, and assess the performance of these materials as catalysts in the transesterification reactions using soybean oil and methanol. The materials were characterized by X-ray diffraction (XRD), vibrational spectroscopy (Fourier transform infrared with attenuated total reflectance (FTIR-ATR)), thermogravimetric analysis coupled to mass spectrometry (TGA DSC-MS), specific surface area, and X-ray photoelectron spectroscopy (XPS). The results of the transesterification reactions showed that the thermal-treated materials from the hydrocalumite intercalated with chloride presented high catalytic activity, among them, the thermal-treated material at 750 °C presented the highest conversion to methyl esters.

ABSTRACT Soil nutrient availability and interpretations of nutrient contents are based on the results obtained from specific extraction methods used in routine testing laboratories. The development of new extraction methods and new extractants with better accuracy is particularly important to determine the correct fertilizer rates to be applied. For this purpose, this study aims to synthesize, characterize and evaluate the predictive capacity of cellulose acetate film containing calcinated layered double hydroxide (CAF-LDH-c), as a new extractant and a new method of P extraction in soils. Different analyses techniques were used to characterize the CAF-LDH-c sample, including X-ray diffraction, attenuated total reflectance Fourier transform infrared spectroscopy, and scanning electronic microscopy. Soils were collected from twelve areas with different management and initial availability of P. The soils were subjected to six rates of P and were cultivated with plants. The predictive capacity of CAF-LDH-c, as a new extractant of P in different soils, was evaluated and compared to Mehlich-1 (M-1), Mehlich-3 (M-3), and Mixed Exchange Resin (MER) extractants. Chemical analyses performed on CAF-LDH-c showed that LDH in powder form was incorporated into the cellulose acetate film. There was a linear relation between P uptake by plants and extractable soil P in the soil by CAF-LDH-c, M-1, M-3, and MER extractants. The significant correlations between extracted P in the soil and P uptake by plants for CAF-LDH-c showed the efficacy of the new extractor and the newly proposed method for different types of soils. The results from the present study confirm the possibility of using CAF-LDH-c extractant as a new methodology to evaluate the availability of P in the soil for plant cultivation.

ABSTRACT Studies aimed at mitigating environmental impacts have received attention in recent years. The use of biochar obtained from the pyrolysis is an alternative for the recovery of organic materials that usually are directly discarded in the environment. Biochar has the potential to recover nutrients from wastewater, and in the latter case, the reuse or recycling of biochar as a controlled-release fertilizer could be an option. However, the adsorption characteristics of the ions into different biochars have not been known. The aim of this study was to evaluate the ions adsorption in biochar derived from discarded potatoes, as well as to make physical and chemical characterization of the produced materials. The biochar derived from discarded potatoes was produced by pyrolysis at 450 °C under an N2 atmosphere. In order to define its ionic profile, the adsorption of HnPO4(3–n)–, Ca2+, Mg2+, and Al3+ was tested in pure biochar, as well as adsorption of HnPO4(3–n)–in biochar after it was doped with Al3+. The desorption of these ions was tested by washing with deionized water, and the KCl (1.0 mol·L–1) and Mehlich-1 extractors. In absolute values, the adsorption order of the ions was Al3+ (in acid pH value) = Ca2+ > Al3+ > HnPO4(3–n)–(biochar doped with Al3+) > Mg2+ > HnPO4(3–n)– (biochar without doping). The adsorption of HnPO4(3–n)– was positively influenced by the doping of biochar with Al3+. The biochar has preferential characteristics for cations adsorption, and the doping process can aid in adsorption of anions.

The objective of this work was to synthesize and characterize Layered Double Hydroxides (MgAl-LDHs, MgFe-LDHs, and MgAlFe-LDHs) containing phosphate anions and study P release kinetics was conducted with the prepared materials. The release kinetics tests were performed in water by the stirred-flow method to verify the P release profile from LDHs materials. Results showed LDHs have similar characteristics to those of reactive sources of P, such as thermophosphates. The LDHs presented gradual P release and the LDH prepared with the molar ratio of cations Mg:Al = 2:1 showed a more sustained profile of P release compared to other produced materials. Thus, the chemical and structural characteristics of the LDHs make them potential materials for the use and storage of slow P release fertilizer.

RESUMO O biocarvão, produto da pirólise de resíduos orgânicos, vem sendo utilizado como condicionador de solo e como alternativa na gestão de resíduos sólidos. O objetivo deste trabalho foi avaliar o efeito da temperatura de pirólise nas propriedades químicas, físicas, mineralógicas e a extração ácida de metais em biocarvões produzidos a partir de resíduos de bagaço da cana-de-açúcar, eucalipto e lodo de esgoto. Foram avaliados os teores de C, H, N, O; cinzas; macro e micronutrientes, além de alguns contaminantes; relações molares O/C e H/C; difratometria de raios X; grupos funcionais por FTIR. Além disso, foi determinada a liberação de nutrientes e contaminantes pela extração em concentrações crescentes de HNO3 (0,01-2,0 mol L-1). As relações O/C e H/C diminuíram com o aumento da temperatura de pirólise, o que caracteriza uma maior estabilidade do C dos biocarvões. O biocarvão de lodo de esgoto (BC-L) apresentou as maiores taxas de liberação de nutrientes e metais contaminantes (Cd, Cr, Ni e Pb). A extração ácida dos demais biocarvões foi muito baixa (< 20% do teor total). Os resultados indicam que a fração carbonosa do biocarvão contribui para a baixa taxa de liberação dos elementos em meio ácido.

ABSTRACT The biochar, product of pyrolysis of organic waste, has been used as a soil conditioner and alternative on solid waste management. However, the raw material and pyrolysis temperature used influence the quantity and dynamics of release of nutrients and contaminants from the biochar. The objective was to evaluate the use of waste sugarcane bagasse, eucalyptus and sewage sludge for production of biochar and determine the chemical, physical, mineralogical properties and acid extraction of these materials produced at 350 °C and 500 °C. Were evaluated the proportion of C, H, N, O; ashes; macro and micronutrients, plus some contaminants; characterization of mineral phases by diffractometry of X- rays; functional groups by infrared absorption spectroscopy (FTIR). Moreover, it was determined the release of nutrients and contaminants for the extraction in increasing concentration of HNO3 (0,01 - 2,0 mol L-1). The O/C and H/C relations decreased with increasing temperature of pyrolysis, which define a greater stability of the C of biochars. Sewage sludge biochar (BC-L) had the highest nutrient release rates and contaminant metals (Cd, Cr, Ni and Pb). Acid extraction of other biochars was very low (<20% of the total content). The results indicate that the carbon fraction of biochar contributes to the low rate of release of the elements in acid place.

Este trabalho de revisão tem como objetivo apresentar os Hidróxidos Duplos Lamelares (HDL) como nanomateriais para serem aplicados na agricultura, com destaque para a utilização desses como matrizes para o armazenamento e a liberação lenta de nutrientes e agroquímicos para o cultivo de plantas. São abordadas as características estruturais, as principais propriedades e os principais métodos de síntese e de caracterização dos HDL. São também reportados trabalhos da literatura, demonstrando a potencial aplicação desses materiais no armazenamento e na liberação lenta de nitrato , fosfato, agroquímicos, além da utilização como adsorventes. Pretende-se com esta pesquisa expandir, em um futuro próximo, o campo de investigação desses materiais com aplicação na agricultura, aumentando a interface entre a química e a agronomia.

The current research aims to introduce Layered Double Hydroxides (LDH) as nanomaterials to be used in agriculture, with particular reference to its use as storage and slow release matrix of nutrients and agrochemicals for plant growing. Structural characteristics, main properties, synthesis methods and characterization of LDH were covered in this study. Moreover, some literature data have been reported to demonstrate their potential for storage and slow release of nitrate, phosphate, agrochemicals, besides as being used as adsorbent for the wastewater treatment. This research aims to expand, in near future, the investigation field on these materials, with application in agriculture, increasing the interface between chemistry and agronomy.

O aumento das emissões dos gases de efeito estufa vem motivando diversos estudos sobre as formas de captura e sequestro de C. A incorporação do biocarvão no solo é uma forma eficiente de manter o C do biocarvão estabilizado, além de propiciar benefícios à produção agrícola. Este trabalho teve como objetivo caracterizar carvões vegetais coletados em diferentes ambientes. Foram determinados os teores de C total e C orgânico; análise elementar através da calcinação; e caracterização das amostras por difratometria de raios X, espectroscopia de absorção e microscopia eletrônica de varredura. As amostras em contato com o solo apresentaram maiores teores de COT, enquanto os teores de C total foram maiores nos carvões sem contato com o solo. Os valores de pH em H2O nas amostras de carvões em contato com o solo variaram de 4,42 a 7,24, com média de 6,8. Já o pH em KCl variou entre 2,91 e 6,88, com média de 4,68. Os teores de nutrientes foram baixos em todas as amostras. Nos carvões em contato com o solo, foram detectados caulinita, quartzo, grafite e gibbsita. Os principais grupos funcionais identificados foram O-H, C=O, C=C e C-O. A MEV das amostras 1 e 2 estruturas da madeira ficaram menos evidentes, e houve influência dos componentes e organismos dos solos nesses carvões..

The increased emissions of greenhouse gases have motivated researches about capture and sequestration of C. The use of biochar in soils is an efficient way to maintain the C in the biochar stabilized and benefit the crop yield. The objective of this research was to characterize charcoals collected at different places.It was determined: total and organic C contents; elementary analysis by calcination; characterization of the samples by X-ray diffractometry, absorption spectroscopy and scanning electron microscopy. The samples in contact with soil showedhigher TOC contents, while total C contents were higher in the charcoals without contact with soil. The pH-H2O values of charcoal samples in contact with soil ranged between 4,42-7,24, average 6,8, while pH-KCl values ranged between 2,91-6,88, average 4,68. All samples presented low nutrient contents. In the samples of charcoal in contact with soil,kaolinite, quartz, graphite and gibbsitewere detected.The main functional groups identified were O-H, C=O, C=C and C-O. In the SEM of thesamples 1 and 2,wood structures were less evident and there was influence of the soil components and organisms in these charcoals.

Nanocompósitos à base de amido de mandioca, argila sintética hectorita e açúcar invertido (plastificante) foram preparados por processo em meio aquoso (casting) produzindo filmes transparentes e homogêneos. Pequenas quantidades de argila (5-15% em massa) produzem principalmente nanocompósitos esfoliados, enquanto grandes quantidades (30% em massa) promovem a formação de nanocompósitos intercalados. Os espectros FT-Raman mostram que bandas sensíveis à ligação de hidrogênio em grânulos de amido são progressivamente deslocadas para frequências menores quando o teor de argila é aumentado. Os nanocompósitos mostram um comportamento térmico semelhante até 320 ºC, enquanto a decomposição da biomolécula em cerca de 500 ºC é dependente do teor de argila. A liberação de CO2 em aproximadamente 300 ºC (decomposição não oxidativa das cadeias poliméricas) diminui se comparada com o desprendimento desse gás em 500 ºC quando a quantidade de argila é aumentada. Filmes com teor de argila maior que 10% não mostram melhora substancial nas propriedades de alongamento ou resistência.

Polymer-clay nanocomposites (PCN) based on cassava starch, synthetic hectorite clay and inverted sugar cane syrup (plasticizer) were prepared by solvent-assisted (casting) process producing transparent and homogeneous films. Small amounts of clay (5-15 wt.%) resulted mainly in exfoliated nanocomposites while large amounts (30 wt.%) promote the intercalated nanocomposites formation. FT-Raman bands sensitive to hydrogen bonding in starch granules are progressively shifted to lower wavenumbers as the clay content is raised. Nanocomposites show a similar thermal behavior up to 320 ºC while the biomolecule decomposition at about 500 ºC is dependent on the clay content. CO2 release at about 300 ºC (non-oxidative decomposition of polymeric chains) decreases if compared to the gas delivery at ca. 500 ºC, as the clay content is increased. Films with clay content higher than 10 wt.% show no substantial benefit for either elongation or resistance properties.

Studies about the inorganic nanoparticles applying for non-viral release of biological and therapeutic species have been intensified nowadays. This work reviews the preparation strategies and application of layered double hydroxides (LDH) as carriers for storing, carrying and control delivery of intercalated species as drugs and DNA for gene therapy. LDH show low toxicity, biocompatibility, high anion exchange capacity, surface sites for functionalization, and a suitable equilibrium between chemical stability and biodegradability. LDH can increase the intercalated species stability and promote its sub-cellular uptake for biomedical purposes. Concerning the healthy field, LDH have been evaluated for clinical diagnosis as a biosensor component.

O objetivo deste estudo foi extrair e concentrar cristais de oxalato de cálcio (CaOx) a partir de folhas de plantas que formam os cristais mencionados. Os estudos químicos e físicos de CaOx de plantas a serem realizados demandam uma massa adequada dos cristais. A planta usada neste estudo foi o cróton (Codiaeum variegatum). As folhas foram trituradas por um liquidificador industrial e peneiradas em peneira de 0,20 mm. Ao suco obtido foi adicionada água destilada. Os cristais foram concentrados no fundo da proveta. É necessário manter a lavagem dos cristais até que o sobrenadante fique livre de pigmentos de plantas e outras substâncias orgânicas. Os cristais de CaOx apresentaram picos bem formados e estreitos, indicando que sua cristalinidade é muito alta; além disso, esses cristais não foram danificados durante o procedimento de extração, o que pode ser visto observando-se as fotos obtidas pelo microscópio eletrônico de varredura. O método apresentado pode ser considerado eficiente para extrair e concentrar cristais de oxalato de cálcio biogênico.

The objective of this study was to extract and concentrate calcium oxalate (CaOx) crystals from plant leaves that form the above mentioned crystals. The chemical and physical studies of CaOx from plant to be performed depend on an adequate amount of the crystals. The plant used in this study was croton (Codiaeum variegatum). The leaves were ground in a heavy duty blender and sieved through a 0.20 mm sieve. The suspension obtained was suspended in distilled water. The crystals were concentrated at the bottom of a test tube. The supernatant must be washed until it is free of plant pigments and other organic substances. Biogenic CaOx crystals have well-defined and sharp peaks, indicating very high crystallinity. Moreover, the CaOx crystals were not damaged during the extraction procedure, as can be seen on the scanning electron microscope images. The porposed method can be considered efficient to extract and concentrate biogenic calcium oxalate.