Lindomar Roberto Damasceno da Silva

NOVEL SUPERABSORBENT HYDROGEL COMPOSITE BASED ON POLY(ACRYLAMIDE-CO-ACRYLATE)/NONTRONITE: CHARACTERIZATION AND SWELLING PERFORMANCE

A novel superabsorbent hydrogel (SH) composite based on a poly(acrylamide-co-acrylate) matrix filled with nontronite (NONT), a Fe(III)-rich member of the smectite group of clay minerals, is described in this manuscript. A variety of techniques, including FTIR, XRD, TGA, and SEM/EDX, were utilized to characterize this original composite. Experimental data confirmed the SH composite formation and suggested NONT was completely dispersed in the polymeric matrix. Additionally, NONT improved the water uptake capacity of the final material, which exhibited fast absorption, low sensitivity to the presence of salt, high water retention and a pH sensitive properties. These preliminary data showed that the original SH composite prepared here possesses highly attractive properties for applications in areas such as the agriculture field, particularly as a soil conditioner.

Activity and selectivity of catalysts based on modified kaolin

Studies of the use of a soil from river Pardo basin located at the Ribeirao Preto region, were realized with the aim of preparing catalysts. A clay, high purity kaolin type, was obtained after purification followed by treatment with acid and then calcined. The activity and selectivity of the catalysts were determined using cycloexene as substrate. The majority of the catalysts obtained yield a conversion higher than 70%.

Síntese e caracterização de hidrogéis compósitos a partir de copolímeros acrilamida-acrilato e caulim: efeito da constituição de diferentes caulins do nordeste brasileiro

Superabsorbent hydrogels based on poly (acrylamide-co-acrylate) and different kaolins, were prepared by free-radical aqueous copolymerization. FTIR and WAXS techniques were employed for characterization of a series of hydrogels, obtained by varying the percentage of clay, crosslinking and constitution of kaolin. The water absorbency at equilibrium (Weq) decreased with increasing clay content and the amount of crosslinking agent. Superabsorbent hydrogel (Weq > 1084 g H2O/g gel) was obtained as 10 wt% of white kaolin and 0.05 mol% of crosslinking agent were used. The hydrogel proved sensitive to pH variation and the presence of salts.

Nitrato de amônio ocluído em zeólita 4A: lixiviação e absorção de nitrogênio no cultivo de milho

Systematic studies were undertaken in the intra zeolitic media to better understand the ability of zeolite type LTA in occluded nitrogen used in fertilizer and soil conditioning. We have measured the dry matter production from the cultivation of corn in a greenhouse for about 40 days, and also the amounts of nitrogen absorbed, retained and lost by leaching. The dry matter production in the cultivation with different concentrations of nitrogen occluded in the zeolite, was more efficient than the traditional fertilizer, which demonstrated better use of nitrogen to reduce leaching losses, which implies a possible reduction of costs for nitrogen.

Influência da calcinação sobre a remoção de ferro da caulinita e ilita e seus efeitos sobre a acidez

Samples of natural clay composed by kaolinite, illite, goethite and quartz, were calcinated and submitted to lixiviation with citrate and chloridric acid in order to remove iron. Investigation due to extraction consequences was carried cut by analyzing its acid properties using ammonia gas as probe in infrared spectrophotometry analysis. The sample that were treated with citrate followed by acid lixiviation yield materials twice more acid than samples treated with acid only.

Study of the effects of lanthanum and the iron ion on the acidic properties of Al-pillared vermiculite

The synthesis of porous materials has attracted interest for decades due to their applications in catalysis and gas adsorption. Clay obtained by insertion of mesoporous oligomer [LaxAl13-xO4 (OH)24 (H2O)12]7 + (where x equals the molar amount of lanthanum), followed by calcination, may cause variation in the acidic properties. The analyzes showed that increasing the amount of La on oligomer results in a higher acidity shown in the spectrum a characteristic band in the region of 1445 and 1545cm-1 to Lewis and Bronsted respectively, predominantly of the last one. The Mossbauer spectroscopy results showed a relationship between increased symmetry of the octahedral site of iron (Fe3+) and increased lanthanum doping, and consequently a sharp increase in acidity.

Caracterização geoquímica, mineralógica, termogravimétrica, e por espectrometria de infravermelho de argilominerais representativos da porção central da Província Borborema

Todas as rochas expostas na superficie sofrem intemperismo. Esse processo leva a formacao de minerais secundarios, entre eles os argilominerais, que sao de larga aplicacao em diversos setores produtivos. Os argilominerais sao silicatos de aluminio hidratados, placoides, do grupo da caulinita, montmorillonita, illita, entre outros, constituidos por particulas de diâmetro inferior a 0,002 mm, depositados como sedimentos fluviais, marinhos, lacustres ou eolicos. Nesse trabalho, foram estudadas caulinita branca e cinza, montmorilonita e nontronita oriundas de depositos localizados na Paraiba e no Rio Grande do Norte, provincia Borborema, nordeste do Brasil. Estes materiais apresentam elevado potencial tecnologico, servindo de base de estudo para a producao de adsorventes de contaminantes oriundos de derivados de petroleo, por exemplo. As amostras foram caracterizadas por difratometria de raios X (DRX), analise termogravimetrica (ATG), capacidade de troca cationica (CTC), espectrometria de infravermelho (IR), e microscopia eletronica de varredura (MEV). As analises quimicas das argilas estudadas revelaram elevados teores de SiO 2 e Al 2 O 3 e teores < 10% para TiO 2 , CaO, MgO, Na 2 O e BaO; montmorilonita apresenta altos teores de Fe 2 O 3 (~13%). A caulinita analisada possui, como impurezas, oxidos e hidroxidos de ferro. A montmorilonita e o principal mineral contido nas argilas bentoniticas da regiao. As amostras de montmorilonita sao argilas naturais e possuem elevada capacidade de adsorcao cationica e, portanto, provavelmente eficiente em posteriores ensaios com essa finalidade. Palavras-chave : Argilominerais, Provincia Borborema; Caracterizacao de minerais.

Avaliação da liberação de NH 4 NO 3 ocluido em zeólita 4A a partir de soluções salinas

The zeolite 4A was used to evaluate the thermo kinetics parameters of NH4+ and NO3- ions occluded in its structure. The Osawa method for activation energy calculation was used to evaluate its thermal stability, and the results shown that the ion species interact differently depending on the zeolite pores, which determines the controlled release by its structure.