Employ a Clay@TMSPDETA hybrid material as an adsorbent to remove textile dyes from wastewater effluents.

A grafting of N1-(3-trimethoxysilylpropyl)diethylenetriamine (TMSPDETA) on natural clay was carried out to obtain an organic-inorganic hybrid clay material that was applied as an adsorbent to the uptake of Reactive Blue 19 (RB-19) and Reactive Green 19 (RG-19) dyes from aqueous wastewaters. This research demonstrates the effect of TMSPDETA contents on amino-functionalized clay materials' hydrophobic/hydrophilic behavior. The resultant material was utilized to uptake reactive dyes in aqueous solutions. The clay@TMSPDETA hybrid material was characterized by isotherm of adsorption and desorption of nitrogen, FTIR, elemental analysis, TGA, pHpzc, total acidity, total basicity groups, and hydrophilic balance. The hybrid samples were more hydrophilic than the pristine clay for ratios from 0.1 up to 0.5 due to adding amino groups to the pristine clay. FTIR spectra suggest that TMSPDETA was grafted onto the clay. The hybrid material presents a surface area 2.17-fold (42.7 m2/g) lower than pristine clay (92.7 m2/g). The total volume of pores of hybrid material was 0.0822 cm3/g, and the pristine clay material was 0.127 cm3/g, corresponding to a diminution of the total pore volume (Vtot) of 1.54 times. The kinetic data followed the pseudo-second-order (PSO) model for RB-19 and RG-19 reactive dyes. The equilibrium data were better fitted to the Liu isotherm model, displaying a Qmax as 178.8 and 361.1 mg g-1 for RB-19 and RG-19, respectively, at 20.0 °C. The main mechanism of interactions of the reactive dyes with the hybrid clay is electrostatic interaction. The clay@TMSPDETA has a very good effect on treating synthetic dye-textile wastewater. The removal percentage of simulated wastewater was up to 97.67% and 88.34% using distilled water and plastic industry wastewater as the solvents, respectively. The clay@TMSPDETA-0.1 could be recycled up to 5 cycles of adsorption and desorption of both dyes, attaining recoveries of 98.42% (RB-19) and 98.32% (RG-19) using 0.1 M HCl + 10% ethanol.

Composite of methyl polysiloxane and avocado biochar as adsorbent for removal of ciprofloxacin from waters.

Two carbon composite materials were prepared by mixing avocado biochar and methyl polysiloxane (MK). Firstly, MK was dissolved in ethanol, and then the biochar was added at different times. In sample 1 (R1), the time of adding biochar was immediately after dissolving MK in ethanol, and in sample 2 (R2), after 48 h of MK dissolved in ethanol. The samples were characterized by nitrogen adsorption/desorption measurements obtaining specific surface areas (SBET) of 115 m2 g-1 (R1) and 580 m2 g-1 (R2). The adsorbents were further characterized using scanning electron microscopy, FTIR and Raman spectroscopy, adsorption of vapors of n-heptane and water, thermal analysis, Bohem titration, pHpzc, and C H N elemental analysis. R1 and R2 adsorbents were employed as adsorbents to remove the antibiotic ciprofloxacin from the waters. The t1/2 and t0.95 based on the interpolation of Avrami fractional-order were 20.52 and 246.4 min (R1) and 14.00 and 157.6 min (R2), respectively. Maximum adsorption capacities (Qmax) based on the Liu isotherm were 10.77 (R1) and 63.80 mg g-1 (R2) for ciprofloxacin. The thermodynamic studies showed a spontaneous and exothermic process for both samples, and the value of ΔH° is compatible with physical adsorption.

Remoção dos compostos odoríferos geosmina e 2-metilisoborneol de águas de abastecimento através de processos de aeração em cascata, dessorção por ar e nanofiltração / Removal of the odoriferous compounds geosmin and 2-methylisoborneol from drinking water by the processes of cascade aeration, air strippingand nanofiltration

Atividades humanas aceleram o processo natural de eutrofização das águas, favorecendo a floração de algas e cianobactérias. Estes organismos emitem os compostos 2-metilisoborneol (MIB) e geosmina, que conferem gosto e odor de mofo e terra à água. A presença destes compostos se estende à água potável uma vez que os processos convencionais de tratamento são insuficientes para removê-los. Esta pesquisa foi realizada com o objetivo de avaliar alternativas de processos de tratamento para a remoção de MIB e geosmina da água. Os processos estudados foram aeração em cascata, dessorção por ar e nanofiltração. Os resultados sugerem a possibilidade de remoção quase total de MIB e geosmina da água através do sistema de nanofiltração, enquanto que os processos baseados em aeração e dessorção foram relativamente ineficientes.

Human activities accelerate the natural process of eutrophication, favouring the occurrence of algae and cyanobacterial blooms. These organisms emit the compounds 2-methylisoborneol (MIB) and geosmin, which confer earthy and moldy taste and odor to water. The presence of MIB and geosmin is extended to drinking water inasmuch they are not completely removed by the processes used in conventional treatment. This research was conducted to evaluate the capability of alternative treatment processes to remove MIB and geosmin from water. The processes studied were cascade aeration, air stripping, and nanofiltration. The results suggested that MIB and geosmin can be almost completely removed by nanofiltration, while the processes based on aeration and stripping were relatively inefficient.

Aplicação de princípios de bioenergética no cálculo da estequiometria de reações biológicas em processos de tratamento de águas residuárias / Application of bioenergetic principles to the stoichiometry of biological reactions in wastewater treatment processes

O tratamento biológico de águas residuárias é realizado por microrganismos que utilizam determinado substrato para obtenção de energia e crescimento celular através de reações de oxidação-redução e fermentação. Esses mecanismos podem ser expressos por meio de reações estequiométricas desenvolvidas a partir de princípios da termodinâmica. As reações são dependentes dos compostos doadores e aceptores de elétrons. As equações balanceadas resultantes permitem estimar as necessidades de nutrientes, a variação de pH/alcalinidade, a produção de biomassa e gases e o coeficiente de produção celular associados aos sistemas biológicos de tratamento. Esta nota técnica descreveu a metodologia para cálculo estequiométrico de reações bioquímicas usando princípios de bioenergética, apresentando exemplos para diferentes substratos e aceptores de elétrons.

Biological wastewater treatment is performed by microorganisms by means of oxidation-reduction and fermentation reactions that release energy for growth and maintenance. These processes can be represented by stoichiometric reactions developed based on thermodynamic principles. Reactions are dependent on the compounds used as electron donor and acceptor. The overall stoichiometric reactions allow estimations of nutrient requirements, alkalinity/pH changes, biomass and gas production, and yield coefficient. This article described a methodology for stoichiometry calculations using bioenergetic principles, presenting examples with different substrates and electron acceptors.