Utilization of Non-Living Microalgae Biomass from Two Different Strains for the Adsorptive Removal of Diclofenac from Water

Ricardo Coimbra,Nadyr Vázquez,Carla Escapa,Guillermo Noriega-Hevia,Marta Otero

doi:10.3390/w10101401

Ricardo Coimbra, Nadyr Vázquez + Show 3 more

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https://doi.org/10.3390/w10101401

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Abstract

In the present work, the adsorptive removal of diclofenac from water by biosorption onto non-living microalgae biomass was assessed. Kinetic and equilibrium experiments were carried out using biomass of two different microalgae strains, namely Synechocystis sp. and Scenedesmus sp. Also, for comparison purposes, a commercial activated carbon was used under identical experimental conditions. The kinetics of the diclofenac adsorption fitted the pseudo-second order equation, and the corresponding kinetic constants indicating that adsorption was faster onto microalgae biomass than onto the activated carbon. Regarding the equilibrium results, which mostly fitted the Langmuir isotherm model, these pointed to significant differences between the adsorbent materials. The Langmuir maximum capacity (Qmax) of the activated carbon (232 mg∙g−1) was higher than that of Scenedesmus sp. (28 mg∙g−1) and of Synechocystis sp. (20 mg∙g−1). In any case, the Qmax values determined here were within the values published in the recent scientific literature on the utilization of different adsorbents for the removal of diclofenac from water. Still, Synechocystis sp. showed the largest KL fitted values, which points to the affinity of this strain for diclofenac at relative low equilibrium concentrations in solution. Overall, the results obtained point to the possible utilization of microalgae biomass waste in the treatment of water, namely for the adsorption of pharmaceuticals.

Highlights

Microalgae are photosynthetic microorganisms capable of using CO2 as a carbon source
Microalgae from two different genera were used in this work: (i) Scenedesmus sp. (SAG 276-1), which was purchased from the Sammlung von Algenkulturen der Universität Göttingen (Culture Collection of Algae at Göttingen University, international acronym SAG); and (ii) Synechocystis sp., which was isolated from natural freshwater in the surroundings of the province of León [22]
The decrease in diclofenac concentration observed in experiments was expected to be related just to adsorption onto the corresponding material

Summary

Introduction

Microalgae are photosynthetic microorganisms capable of using CO2 as a carbon source. As the accumulation of CO2 in the atmosphere is one of the most serious environmental issues to be faced nowadays, the possibility of using microalgae for its sequestration has received great attention [1]. The implementation of CO2 sequestration by microalgae is mostly limited by techno-economic constrains [2]. An option to increase the cost-effectiveness is the cultivation of microalgae in wastewater, which is a complex mixture that may serve as a source of nutrients and water [3]. This strategy allows for nutrient recycling with savings in microalgae cultivation costs and, simultaneously contributes to enhancing the sustainability of wastewater treatment [4,5].

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