Resumo Cas·cas de sem·entes de M. oleifera (H-MO) fora·m usadas com·o adsorve·nte para remo·ver o coran·te az·ul de metile·no (MB) de uma solu·ção aqu·osa. O adsorve·nte foi caracte·rizado por ME·V, ED·S, DRX, FT·IR, B·ET e pH·PCZ. Para aval·iar a capacid·ade de adsor·ção, foi ana·lisada a influ·ência do pH, ciné·tica, isoter·mas e propr·iedades termo·dinâmicas. Técnic·as de caracter·ização indic·aram que a H-MO poss·ui caracter·ísticas morfológ·icas hetero·gêneas com á·rea supe·rficial espe·cífica de 3,24 m2 g-1, co·mposta prin·cipalmente por celu·lose distr·ibuída em estr·utura am·orfa. A adso·rção de MB foi favo·rável em va·lores de pH supe·riores a pHP·CZ de 6,6, utili·zando uma dosa·gem de ads·orvente de 1,0 g L-1. O equ·ilíbrio foi alca·nçado nos prim·eiros 240 min, e o mode·lo de pseu·do seg·unda or·dem foi adequa·do para desc·rever os dad·os cin·éticos. Fre·undlich foi o mo·delo mais ade·quado para des·crever as curvas isot·érmicas, preve·ndo uma cap·acidade máx·ima de ads·orção de 122,7 mg g-1 a 24°C, supe·rior a ou·tros adsor·ventes nat·urais. O pro·cesso de adsor·ção foi esp·ontâneo e exoté·rmico, indi·cando que temper·aturas mais ba·ixas favor·ecem a adsor·ção e que ela é con·trolada por for·ças físi·cas. Os d·ados aprese·ntados indi·cam que o M·B tem· po·tencial para ser tr·atado com suc·esso pelas ca·scas de semen·tes de M. oleif·era, um adsorvente ecol·ogicamente favo·rável e de ba·ixo custo.

Abstract M. ole·ifera se·ed hu·sks (H-M·O) w·ere u·sed as adsorbent for the removal of methylene blue (MB) dye from an aqueous solution. The ads·orbent was char·acterized by SE·M, ED·X, X·RD, F·TIR, B·ET, and p·HPZC. To evaluate adsorption capacity, the influences of p·H, kinetics, isotherms, and thermodynamic prop·erties were anal·yzed. Characteri·zation tech·niques indic·ated that H-MO has het·erogeneous morp·hological charac·teristics wi·th a spe·cific sur·face a·rea of 3.24 m2 g-1, mai·nly comp·osed of ce·llulose distr·ibuted in an amor·phous stru·cture. MB adsorption was favorable at pH values higher than pHPZC of 6.6, using an adsorbent dosage of 1.0 g L-1. Equilibrium was achieved in the first 240 min, and the pseudo-second-order model was suitable for describing the kinetic data. Freu·ndlich was the mo·st adeq·uate model for descri·bing the isoth·erm cur·ves, pred·icting a max·imum adsor·ption capa·city of 122.7 mg g-1 at 24°C, hig·her tha·n oth·er natu·ral ad·sorbents. The ads·orption proc·ess w·as spo·ntaneous and exoth·ermic, indic·ating that lo·wer temper·atures fav·or the ad·sorption and th·at it is cont·rolled by p·hysical fo·rces. The da·ta presen·ted indic·ate the M·B has t·he pot·ential to be succ·essfully trea·ted by the eco-fr·iendly and l·ow-cost ads·orbent M. oleif·era seed h·usks.

RESUMO O sulfato de alumínio (SA) é amplamente utilizado como coagulante no tratamento de água de abastecimento via ciclo completo. Coagulantes alternativos estão disponíveis no mercado, dentre eles o cloreto de polialumínio (PAC). Porém, estudos comparativos entre o SA e os PACs de alta (PAC-AB) e baixa (PAC-BB) basicidade em relação à cinética de floculação ainda são escassos. Nesse sentido, o intuito deste trabalho foi comparar o uso de PAC-BB, PAC-AB e SA via coagulação, floculação e sedimentação, bem como avaliar o efeito na condutividade elétrica, na formação de lodo, na alcalinidade, no pH e na remoção de turbidez baseado na cinética de floculação e morfologia do floco formado. Os resultados indicaram aumento de 8,1% na condutividade elétrica e de 30,6 mg.L-1 na formação de lodo; não houve diferença significativa entre os coagulantes. O PAC-AB apresentou menor consumo de alcalinidade e, consequentemente, menor redução no pH. A remoção de turbidez foi estatisticamente igual entre o PAC-BB (91,8 ± 3,7%) e o PAC-AB (91,5 ± 1,1%), porém maior que no SA (82,2 ± 6,4%). Essa diferença se acentua com o aumento da velocidade crítica de sedimentação. A constante de agregação dos flocos (K A ) apresenta resultados estatisticamente iguais entre os coagulantes, e o melhor desempenho de remoção de turbidez dos PACs em relação ao SA se deve à menor constante de ruptura do floco (K B ), podendo-se inferir, portanto, que os flocos formados com o PAC-AB e o PAC-BB são mais fortes que os formados com o SA.

ABSTRACT Aluminum sulfate (AS) is widely used as a coagulant in conventional drinking water treatment facilities. Alternative coagulants are commercially available, including polyaluminium chloride (PAC). However, comparative studies between AS and PAC with high (PAC-AB) and low (PAC-BB) basicity regarding flocculation kinetics are still scarce. In this sense, the aim of this work is to compare the use of PAC-BB, PAC-AB, and AS via coagulation, flocculation, and sedimentation as well as to evaluate the effect on electrical conductivity, sludge formation, alkalinity, pH, and turbidity removal based on flocculation kinetic and floc morphology. The results indicated that the increase in electrical conductivity was 8.1% and the sludge formation was 30.6 mg.L-1, and that there was no significant difference between coagulants. PAC-AB presented the lowest alkalinity consumption and, consequently, the lowest pH reduction. Turbidity removal was statistically equal between PAC-BB (91.8 ± 3.7%) and PAC-AB (91.5 ± 1.1%), but higher than in AS (82.2 ± 6.4%). This difference is accentuated with the increase in critical settling velocity. The floc aggregation constant (K A ) is statistically equal among the coagulants, and the better turbidity removal performance of the PACs in relation to the AS is due to the lower floc breaking constant (K B ) and may, therefore, infer that the flocs formed with PAC-AB and PAC-BB are stronger than those formed with SA.

Abstract Titanium and its alloys are widely used as implant materials and many studies to accelerate the osseointegration have been performed. This work aims to evaluate the formation of a bioactive surface in commercially pure titanium (cp-Ti) grade 4 after alkali (AT) and heat treatments at 600 °C (AHT600) and 900 °C (AHT900). Characterization techniques were SEM, AFM, Raman, TF-XRD, wettability, nanoindentation and indentation adhesion. Additionally, SBF soaking tests were performed to evaluate apatite growth and showed that alkali and heat treatment accelerates apatite growth. The AT samples formed sodium hydrogen titanate (1 µm thick), and AHT600 and AHT900 formed sodium titanate (1 µm thick), while rutile TiO2 increased with temperature, reaching up to 5 µm thick and the surface changed from slightly hydrophilic to fully hydrophilic. Roughness and surface area increased, especially in AHT900. The hardness of the surface layer was significantly increased by the heat treatment.

RESUMO Cloreto de polialumínio (PAC) é um coagulante polimérico inorgânico pré-hidrolisado que tem se destacado no tratamento de água de abastecimento e residuária por formar um precipitado de Al(OH)3* rígido e pesado, além de ter baixo efeito no pH. A literatura, porém, ainda é escassa na correlação da química e da física do coagulante com otimizações de processo. Nesse sentido, o objetivo deste trabalho foi empregar o PAC em estudos de tratabilidade de água de abastecimento via coagulação, floculação e sedimentação. Para isso, inicialmente foi feito um modelamento matemático para ajuste de turbidez e pH e construídos diagramas de coagulação de turbidez e de cor aparente remanescentes com pH de 4,0 a 9,0 e dosagem de 10 a 120 mg.L-1 de PAC (0,6 a 6,9 mg.L-1 de Al3+). Também foram estudados diferentes gradientes de velocidade e tempos de mistura para a coagulação e a floculação. Os diagramas de coagulação apresentaram resultados satisfatórios na faixa de pH entre 7 e 9 com dosagem superior a 30 mg.L-1 de PAC (1,7 mg.L-1 de Al3+), e está relacionado com a solubilidade mínima do Al(OH)3*. Otimizações da coagulação e da floculação obtiveram melhora de até 79% da turbidez remanescente, redução de até 83% da área do sedimentador ou redução de até 67% na dosagem de PAC, em razão de um aumento do tamanho do floco produzido. Um conhecimento aprofundado da química e da física do processo relacionado ao uso do PAC pode, portanto, trazer benefícios ao seu uso.

ABSTRACT Polyaluminium chloride (PAC) is a pre-hydrolyzed inorganic polymeric coagulant that is being used widely in the treatment of water supply and wastewater by forming a hard and heavy Al(OH)3* precipitate, in addition to having a smaller effect on pH. The literature, however, is still scarce in correlating the chemistry and physics of the coagulant with process optimizations. The objective of this paper is to use PAC in studies of water supply treatability through coagulation, flocculation, and sedimentation. For this purpose, a mathematical modeling was initially performed to adjust turbidity and pH, and then remaining turbidity and apparent color coagulation diagrams were constructed with a pH of 4.0 to 9.0 and a dosage of 10 to 120 mg.L-1 of PAC (0.6 to 6.9 mg.L-1 of Al3+). Different gradients of velocity and mixing times for coagulation and flocculation were also studied. The coagulation diagrams indicated satisfactory results in the pH range between 7 and 9 with a dosage higher than 30 mg.L-1 of PAC (1.7 mg.L-1 of Al3+), and it is related to the minimum solubility of Al(OH)3*. Coagulation and flocculation optimizations achieved an improvement of up to 79% in the remaining turbidity, a reduction of up to 83% in the settler area or a reduction of up to 67% in PAC dosage, due to an increase in the size of the floc produced. An in-depth knowledge of the chemistry and physics of the process related to the use of PAC can, therefore, bring benefits to its use.

The objective of this study is to evaluate the surface physicochemical properties of Ti6Al4V alloy after etching with a piranha’s solution at temperatures of 25 °C, 40 °C, and 60 °C for 30 min. Scanning electron microscopy with energy-dispersive X-ray spectroscopy, optical profilometry, X-ray diffraction, and wettability analyses were used to characterize the surface of the samples. In addition, corrosion tests were performed using potentiodynamic polarization and electrochemical impedance spectroscopy. The proposed surface treatment did not alter the wettability and surface chemistry (crystallinity), but the texture, surface roughness, superficial area, and corrosion resistance of the alloy could be changed by varying the etching temperature. Considering that these properties are indirect indicators of the alloy’s potential success in the osseointegration of a dental implant, the surface treatment of the Ti6Al4V alloy using a piranha solution while controlling the etching temperature has attractive biomedical applications.

Resumo O objetivo deste estudo é avaliar o uso de semente de Moringa oleifera (MO) como um coagulante natural para remoção de turbidez e cor aparente no tratamento de água de abastecimento com baixa turbidez inicial via técnica de filtração direta em linha. A morfologia e carga de superfície foram investigadas por técnicas de caracterização como microscopia óptica, tamanho de partícula a laser e potencial zeta. As proteínas catiônicas da semente de MO foram extraídas em meio aquoso. Os ensaios de Jar test apontaram que os padrões de potabilidade para turbidez e cor foram atingidos na faixa de pH de 4,0 a 8,5 e dosagens ≥ 5 mg L-1 de MO. O mecanismo de coagulação dominante é o de adsorção e neutralização de carga. O estudo evidencia que é possível tratar água de baixa turbidez com semente de MO pela técnica de filtração direta em linha.

Abstract This study evaluated the use of Moringa oleifera (MO) seed as a natural coagulant for the removal of turbidity and apparent color in the water treatment with low initial turbidity through the in-line filtration technique. The morphology and surface charge were investigated by characterization techniques such as optical microscopy, laser particle size, and zeta potential. The cationic proteins of the MO seed were extracted in aqueous solution. The jar test showed the potability standards for turbidity and apparent color were reached in the pH range from 4.0 to 8.5 and dosages ≥ 5 mg L-1 of MO. The dominant coagulation mechanism is adsorption and charge neutralization. This study showed that treating low-turbidity water with MO seed by the in-line filtration technique is possible.

Plasma nitriding of a solution annealed and aged 300 grade maraging steel was studied aiming to increase the creep resistance. The surface microhardness reached 1,140 HV, producing 50 µm layer composed of ε-Fe3N and γ'-Fe4N nitrides at the uppermost sample layer. The inner core remained unaltered presenting typical plate-like martensite microstructure of maraging steels with average microhardness of 604 HV. Surface RMS roughness in the nanometric scale increase from 52 nm to 71 nm. The continuous layer of iron nitrides seems to behave as a barrier for oxidation and for inward oxygen diffusion improving the creep resistance by reducing the steady-state creep rate (εs) in 52-65% when compared with the literature results. Dominant creep mechanism is controlled by dislocations climb. Fracture surfaces of specimens presented ductile failure consisting of equiaxed and bi-modal dimples in the fibrous zone surrounded by 45º shear lip. Nitrided sample presented a reduced ductility, associated to the hard surface layer.

ABSTRACT: The objective of this paper is to analyze the influence of specific laser system parameters on the microstructure of the ring formation process on the hard metal tool's surface. The parameters analyzed were: working distance, incident beam power and tool surface treatment, flank and rake. The microstructures were analyzed with regard to its diameter and depth by an optical 3-D surface metrology instrument. The analyses were made by comparing the ring's process formation with the dimples' process formation, a well-known process called ablation. The results show that the ring's diameter is increased by increasing incident beam power or the distance of the laser beam's focus for both surfaces. In addition, increasing the working distance decreases the ring's depth for both surfaces.