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Due to lead (Pb) being highly toxic and harmful to living beings, several techniques have been studied aiming at its removal from contaminated water, with great emphasis on the adsorption process. In this sense, the objective of this study was to investigate if the chemical functionalization in biosorbents of Moringa oleifera pods promotes greater potential in the process of removing lead from aqueous solution. To this end, characterization of biomass was performed by energy dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy analysis, scanning electron microscopy, X‐ray diffraction, and zero load point. Additionally, the parameters that influence the efficiency of lead biosorption have been investigated. From the studied parameters, the optimal conditions obtained for both analyzed biosorbents are as follows: 30 min to equilibrium, pH 6 and 25°C temperature. Biosorption studies revealed kinetic modeling of data were better represented by the pseudo‐second model. In relation to adsorption isotherms, the model that best fit the experimental data were the Langmuir model for both biosorbents. When comparing the biosorbents studied, it was concluded that chemical functionalization carried out using basic treatment agent was the most efficient in removing lead ions (II), and the maximum adsorption capacity obtained was 38.52 mg/g. [ABSTRACT FROM AUTHOR]

Considering the need for new technologies for the removal of pesticides from the aqueous environment, the Moringa oleifera seed husks (h-MO) were investigated for the diuron adsorption from contaminated water at different temperatures and solute concentrations. The biosorbent used in this study was characterized by chemical, structural and textural analyses. The best experimental condition for the biosorption was determined by evaluating the mass of the biosorbent and the pH solution. We found a good adsorption capacity for the herbicide where the maximum adsorption capacity was 14.74 mg/g at pH 5 and 45°C. In addition, the adsorption process of diuron by the h-MO occurred spontaneously, in which, ΔG° values increased as the temperature increased, meaning that the process tends to a more energetically favourable process at higher temperatures. Both Langmuir and Sips isotherm models presented satisfactory adjustment at all temperatures and the pseudo-second-order model presented the best fit for the experimental results. The application of the intra-particle diffusion model showed that the adsorption process started instantaneously through the boundary layer of the adsorbent and that the pore diffusion step was a limiting step in the process. Finally, the capacity of the h-MO was compared with other adsorbents that had been used for diuron removal from contaminated where it was found that the adsorption capacity of the h-MO is much higher than other natural adsorbents. [ABSTRACT FROM AUTHOR]

The present study proposes development of an adsorbent based on combination of graphene oxide (GO) and iron oxide (α-γ-Fe2O3) nanoparticles for atrazine removal from water. The synthesized adsorbent (GO@ α-γ-Fe2O3) was characterized using different techniques. Magnetic measurements proved that the adsorbent has superparamagnetic characteristics, thus facilitating its magnetic separation from the working suspensions. The maximum adsorption capacity was 42.5 mg g−1. The Langmuir isotherm and the pseudo-second order kinetic models correlated adequately with the experimental data. The thermodynamic data showed that atrazine adsorption was spontaneous, endothermic and thermodynamically favorable. [ABSTRACT FROM AUTHOR]

The present research evaluates the groundwater nitrate concentration of the Maringá region (Paraná State, Brazil) aiming at nitrate removal by coagulation/flocculation using a natural coagulant obtained from the seeds of the Moringa oleifera Lam. plant (MO) combined with an activated carbon filter. Groundwater samples were collected in Maringá City metropolitan area and characterized by physicochemical analyses. The results showed groundwater NO3− concentrations ranging from 0-60 mg NO3− L−1. Thus, the nitrate variation in the water used in the coagulation/flocculation assays lay between 10-60 mg · L−1 of NO3−. In these assays both aqueous and saline MO raw extracts were added (concentrations between 0.25-11 g · L−1). Coagulation/flocculation treatment with aqueous MO extract presents nitrate removal of 73.3 %, and saline MO extract presents 85.4 %. The source that presented the highest nitrate concentration along with the ideal MO concentration in the coagulation/flocculation process was used for the coagulation/flocculation process followed by activated carbon filtration. The treatment with MO combined with the filter met Brazilian, American, and international potability standards for nitrate and turbidity. The present study reveals the presence of nitrate in the groundwater of the area and also enables new procedures for treating this kind of water in small rural properties and needy communities. [ABSTRACT FROM AUTHOR]

Background: Candida rugosa Lipase (CRL) shows a very low alkaline stability that comprises its immobilization on glyoxyl-agarose, which requires pH above 10. In this way, an adaptation from the original method was used; an enzyme solution at pH 7 was slowly added at a suspension of glyoxyl-agarose prepared in bicarbonate buffer, pH 10. This change of protocol was enough for allowing the preparation of derivatives actives of CRL on glyoxyl-agarose and verifying the effect of this modified procedure on the properties of the immobilized enzyme. The effect of the additives Triton-X-100 and polyethylene glycol (PEG) on the enzymatic activity recovery and immobilized enzyme stability was evaluated., Methods: The glyoxyl-agarose support was prepared by etherification of 6% agarose beads with glycidol and further oxidation with sodium periodate. CRL was immobilized covalently on glyoxyl-agarose support in the absence and presence of 1% (w/v) Triton-X-100 or 5 g L -1 polyethylene glycol (PEG). The lipolysis activity of the free and immobilized enzyme was determined at 37ºC and pH 7.0, using p-nitrophenyl palmitate (p-NPP) as substrate. Profiles of temperature-activity (37-65ºC, pH 7.0) and pH-activity (6.0-9.5, 37ºC) were evaluated as well as thermal (45ºC and pH 8.0) and operational (15 min batches of p-NPP hydrolysis at 50ºC and pH 8.0) stabilities of free and immobilized CRL., Results: Using a single modification of the original protocol, the CRL poorly stable under alkaline conditions could be immobilized on glyoxyl-agarose in its active conformation (recovered activity varying from 10.3 to 30.4%). Besides, the presence of a detergent (Triton-X-100) and an enzyme stabilizer (PEG) contributed to the preparation of more active and more stable biocatalysts, respectively. CRL immobilized on glyoxyl-agarose in the presence of PEG was around 5 times more stable than the free CRL and around 3 times more stable than the CRL immobilized on glyoxyl-agarose in absence of PEG. The higher stability of the CRL-glyoxyl derivative prepared in the presence of PEG allowed its reuse in four successive 15 min-batches of p-nitrophenyl palmitate hydrolysis at 50ºC and pH 8.0., Conclusion: The technique of immobilizing enzymes covalently on glyoxyl-agarose showed promising results for Candida rugosa lipase (CRL). The derivatives prepared in the presence of the additives retained two to three times more activity than those prepared in the absence of additives. The enzyme immobilized in presence of PEG was about three times more stable than the enzyme immobilized in absence of this additive. Maximum catalytic activity of the immobilized CRL (in absence of additives) was observed in a temperature 10ºC above that for the free enzyme and the pH of the maximum activity was maintained in the range 6.5-7.5 for free and immobilized CRL.