Efficient removal of tetracycline, ciprofloxacin, and amoxicillin by novel magnetic chitosan/microalgae biocomposites

Two new highly-efficient and eco-friendly biosorbents comprised of magnetite, chitosan and Chlorella vulgaris (MCC) or Arthrospira platensis (MCA) were prepared in such a way to be easily separated and reused for removing different classes of antibiotics such as tetracycline (TC), ciprofloxacin (CIP) and amoxicillin (AMX) from wastewater. They were characterized using SEM, FTIR and TGA. Biosorption experiments were performed to investigate the impact of pH, biosorbent dosage, initial antibiotic concentration, contact time, and concentration of background electrolytes (NaCl, KCl and CaCl2) on adsorption. Both biocomposites showed outstanding per formance in antibiotics removal. Equilibrium data were modelled using Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption isotherms, among which the first one gave the best fit, with maximum TC, CIP and AMX adsorption capacities of 834.0, 394.9, and 150.8 mg/g for MCA and of 831.1, 374.2, and 140.2 mg/g for MCC, respectively. To follow the adsorption time-evolution, the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models were tested, the second of which proved to be the best-fitting one. Thermodynamic parameters revealed that adsorption was spontaneous and endothermic. Both biosorbents were re generated through microwave-assisted treatment and reused repeatedly for up to four cycles, losing TC, CIP and AMX adsorption capacities at equilibrium by no >7, 4 and 9 %, respectively. This study suggests that both biocomposites may be effective and sustainable alternatives to commercial adsorbents for removing antibiotics from wastewater

Chlorella vulgaris and Arthrospira platensis growth in a continuous membrane photobioreactor using industrial winery wastewater

The rapid development of urbanization and industrialization leads to the production of large amounts of wastewater all over the world, which could be exploited to grow microalgae, thereby reducing their cultivation costs and making biofuel production more feasible. In this research work, a co-culture of Chlorella vulgaris and Arthrospira platensis was grown in a continuous flow column membrane photobioreactor using 20% (v/v) of winery wastewater as a medium with the aim of reducing its polluting impact. Three different hydraulic retention times were investigated, namely 4.6, 2,0 and, 1.4 days. Chemical oxygen demand was reduced by more than 75%, and a biomass concentration higher than 4 g Dry Weight/L was obtained with a lipid content higher than 20 g Lipid/100 g Dry Weight. Fatty acids were mainly saturated. The results obtained suggest that C. vulgaris and A. platensis can grow in winery wastewaters, leading to a low-cost biomass production and to a reduction in the environmental impact of the industrial effluent used in this study

Kinetics and Isotherms of Mercury Biosorption by Dry Biomass of Arthrospira (Spirulina) platensis

Inorganic mercury was effectively removed from water solutions by means of dry biomass of Arthrospira (Spirulina) platensis as biosorbent. The results obtained at defined pH and biomass concentration as well as variable Hg concentrations were used to estimate biosorption kinetics and isotherm parameters. Biosorption kinetics was best described by the pseudo-first-order model of Lagergren that allowed estimating an average specific rate constant as high as 0.044 min 121, while the Dubinin and Radushkevich model was the best fitting isotherm. Hg biosorption seemed to occur via physisorption. Considering the wide dissemination of A. platensis and its easy cultivation, these results point to its biomass as a low-cost biosorbent to treat Hg-contaminated waters

Large-Eddy Simulation of Oil-Water Annular Flow in Eccentric Vertical Pipes

One of the difficulties related to oil exploration is transporting heavy oil since its high viscosity causes high-pressure drop and energy consumption. In order to save energy, the core annular flow (CAF) can be applied where a two-phase annular flow occurs, with peripheral water flowing offering a reduction in energy expenditure. The multiphase flow was studied experimentally in a simple purpose-built unit. To theoretically handle the CAF, computational fluid dynamics simulations were done with the commercial package Ansys Fluent. The flow was considered turbulent, isothermal, incompressible, and 3D, and both stationary and transient cases were evaluated. The volume-of-fluid model was adopted for the multiphase system, and water/oil interface and turbulence phenomena were well predicted

Arthrospira platensis Cultivation in a Bench\u2010Scale Helical Tubular Photobioreactor

Cultivations of Arthrospira platensis were carried out to evaluate the CO2 capture capacity of this cyanobacterium under bench\u2010scale conditions. For this purpose, the influence of light intensity on the microbial growth and the photosynthetic efficiency has been investigated in a helical photobioreactor. Five cultivations were performed at different photosynthetic photon flux densities (23 64 PPFD 64 225 \u3bcmol photons m 122 s 121 ) by fed\u2010batch pulse\u2010feeding pure carbon dioxide from a cylinder into the helicoidal photobioreactor. In particular, a range of PPFD (82\u2013190 \u3bcmol photons m 122 s 121) was identified in which biomass concentration reached values (9\u201311 gDW L 121) significantly higher than those reported in the literature for other configurations of closed photobioreactors. Furthermore, as A. platensis suspensions behave as Newtonian and non\u2010Newtonian (pseudoplastic) fluids at very low and high biomass concentrations, respectively, a flow analysis was carried out for evaluating the most suitable mixing conditions depending on growth. The results obtained in this study appear to be very promising and suggest the use of this helicoidal photobioreactor configuration to reduce CO2 emissions from industrial gaseous effluents

Flow Synthesis of 2-[Methyl(pyridin-2-yl)amino]ethanol: An Experimental and Computational Study

Microreactor technology is increasingly applied in the chemical-pharmaceutical industry for safer and more efficient drug production as compared to the traditional batch process. This technology is employed for the first time to study the production of 2-[methyl(pyridin-2-yl)amino]ethanol, the first intermediate in rosiglitazone synthesis. Under the optimum operating conditions, a single microreactor chip at 160 \ub0C allowed to produce the equivalent of more than five batch reactors at 120 \ub0C. The kinetic study indicated that the reaction is second order. Thermodynamic parameters were determined by the Eyring equation and density functional theory (DFT) calculations with good agreement. DFT results suggested a concerted nucleophilic aromatic substitution reaction mechanism