RESEARCH ARTICLE Study of the removal mechanism of aquatic emergent pollutants by new bio-based chars Maria Manuel Serrano Bernardo 1 & Catarina Alexandra Catanas Madeira 1 & Nuno Carlos Lapa dos Santos Nunes 2 & Diogo André Costa Messias Dias 2 & Delfina Maria Barbosa Godinho 1 & Maria Filomena de Jesus Pinto 3 & Inês Alexandra Morgado do Nascimento Matos 1 & Ana Paula Batista Carvalho 4 & Isabel Maria de Figueiredo Ligeiro Fonseca 1 Received: 13 March 2017 /Accepted: 9 August 2017 # Springer-Verlag GmbH Germany 2017 Abstract This work is dedicated to study the potential appli- cation of char byproducts obtained in the gasification of rice husk (RG char) and rice husk blended with corn cob (RCG char) as removal agents of two emergent aquatic contaminants: tetracycline and caffeine. The chars presented high ash contents (59.5–81.5%), being their mineral content mainly composed of silicon (as silica) and potassium. The samples presented a strong basic character, which was related to its higher mineral oxides content. RCG char presented better textural properties with a higher apparent surface area (144 m 2 g -1 ) and higher micropore content (V micro = 0.05 cm 3 g -1 ). The alkaline char- acter of both chars promoted high ecotoxicity levels on their aqueous eluates; however, the ecotoxic behaviour was eliminat- ed after pH correction. Adsorption experiments showed that RG char presented higher uptake capacity for both tetracycline (12.9 mg g -1 ) and caffeine (8.0 mg g -1 ), indicating that textural properties did not play a major role in the adsorption process. For tetracycline, the underlying adsorption mechanism was complexation or ion exchange reactions with the mineral ele- ments of chars. The higher affinity of RG char to caffeine was associated with the higher alkaline character presented by this char. Keywords Char . Rice husk . Corn cob . Gasification . Pharmaceutical . Water Introduction Rice and corn are the most produced cereals in the world (FAOSTAT 2016). The Food and Agriculture Organization (FAO) of the United Nations estimates world corn and paddy rice production in 2015 at approximately 1007 and 743 mil- lion tonnes, respectively. Asia is responsible for about 90% of the world paddy rice production (FAO: RMM 2016) and the Americas are the biggest corn producer (approximately 51% of the total world production) (FAOSTAT 2016). Considering that 20% of the paddy grain is composed by husk (Soltani et al. 2015), the world paddy production resulted in approximately 150 million tonnes of rice husk. Concerning maize, the total corn grains produced across the world gener- ated about 15% of the cobs (Zhang et al. 2012), which resulted in approximately 151 million tonnes of corn cobs. The corn cob is usually left in the field as part of the corn stover for soil conditioning. Recently, much attention has been focused on the use of rice husk to produce advanced silicon-based materials as well as construction materials (Shen et al. 2014; Soltani et al. 2015). However, the amount of rice husk and corn cobs Responsible editor: Guilherme L. Dotto Electronic supplementary material The online version of this article (doi:10.1007/s11356-017-9938-9) contains supplementary material, which is available to authorized users. * Maria Manuel Serrano Bernardo maria.b@fct.unl.pt 1 LAQV/REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal 2 LAQV/REQUIMTE, Departamento de Ciências e Tecnologia da Biomassa, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal 3 Unidade de Bioenergia, Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, Ed. J, 1649-038 Lisbon, Portugal 4 Centro de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisbon, Portugal Environ Sci Pollut Res DOI 10.1007/s11356-017-9938-9