Produção de adsorventes à base de resíduos para a remoção de fármacos da água: ativação química e modificação

The sustainable development of society implies the adoption of strategies related to waste management and valorization (in a circular economy perspective) and to effluent treatment (namely for the removal of pharmaceuticals from water). Being adsorption by activated carbon (AC) a well-established method for water treatment, this work focuses on the production of AC using residues, namely sludge from pulp and paper industry, for the removal of pharmaceuticals from water. This approach aims to foster an integrated solution for the two environmental issues involved in this work. Primary pulp and paper mill sludge (PS) showed a great potential to produce carbon-based adsorbents, relatively to biological sludge (BS). Through the use of PS and a production process involving chemical activation and pyrolysis, it was possible to produce AC in both powdered and granular (using a binder agent) forms, with high surface areas (SBET) (similar to those of commercial AC with the same granulometry). The produced powdered AC presented, in batch adsorption systems, adsorption capacities for the pharmaceuticals carbamazepine (CBZ), sulfamethoxazole (SMX) and paroxetine (PAR), in the same magnitude of commercial AC. However, when applied in wastewater matrix, variations in the adsorption capacity of the produced AC for the studied pharmaceutical was observed, namely in the case of SMX, which decreased, and PAR, that increased. The produced granular AC showed, in batch adsorption systems, lower adsorption capacity for the three pharmaceuticals CBZ, SMX, and PAR, than the commercial granular AC used as reference. Also, in this case, a reduction in the adsorption capacity for CBZ and SMX was observed for wastewater matrices. In fixed-bed column studies (continuous mode) the produced granular AC presented a higher breakthrough volume and adsorption capacity for CBZ for the lower flow-rate. Also, it was observed a reduction of the adsorption capacity with the increase of the complexity of the aqueous matrix (distilled water > wastewater > multicomponente solutions – with the three pharmaceuticals – in wastewater). The application of different functionalization methods to the powdered AC surface showed to be an interesting approach, evidencing an increase in the selectivity of some functionalized AC for some of the pharmaceuticals under study, despite the general reduction in their SBET. Concluding, this work demonstrates the potential of PS from pulp and paper mill industry to produce alternative AC, particularly in the powdered form, to be applied in the removal of pharmaceuticals from water.O desenvolvimento sustentável da sociedade implica a adoção de estratégias ligadas à gestão dos resíduos e sua valorização (numa perspetiva de economia circular) e ao tratamento de efluentes (nomeadamente, para a remoção de fármacos da água). Sendo o processo de adsorção por carvão ativado (CA) um método bem estabelecido para o tratamento de águas, este trabalho incide sobre a produção de CA a partir de resíduos, nomeadamente lamas da indústria da pasta e do papel, para a remoção de fármacos da água. Esta abordagem pretende proporcionar uma solução integrada nos dois desafios ambientais anteriormente referidos. Comparativamente com as lamas biológicas (LB), as lamas primárias (LP) da indústria da pasta e do papel, mostraram ter um grande potencial para a produção de adsorventes à base de carvão. A partir de LP, e usando um processo de ativação química e pirólise, foi possível produzir CA, quer na forma de pó, quer na forma granular (usando um agente aglomerante) com elevadas áreas superficiais (SBET) (comparáveis às de CA comerciais da mesma granulometria). Os CA produzidos em pó apresentaram, em sistemas descontínuos de adsorção, capacidades de adsorção para os fármacos carbamazepina (CBZ), sulfametoxazol (SMX) e paroxetina (PAR), da mesma ordem de grandeza que os CA comerciais. Contudo, quando aplicados em matrizes de efluente real, observam-se variações na capacidade de adsorção dos CA produzidos para os fármacos em estudo, principalmente no caso do SMX, que diminuiu, e da PAR, que aumentou. O CA granular produzido apresentou, em sistemas descontínuos de adsorção, menor capacidade de adsorção para os três fármacos CBZ, SMX e PAR, do que o CA granular comercial de referência. Também neste caso, se verificou uma redução da capacidade de adsorção da CBZ e do SMX em matrizes de efluente real. Estudos realizados em colunas de leito-fixo (modo contínuo) mostraram que o CA granular produzido apresentou maior volume de rutura e maior capacidade de adsorção da CBZ para o menor fluxo. Verificou-se, ainda, a redução da capacidade de adsorção com o aumento da complexidade da matriz aquosa (água destilada > efluente real > soluções multicomponente - com os três fármacos - em efluente). A aplicação de diferentes metodologias de modificação ou funcionalização da superfície dos CA em pó mostrou ser uma abordagem interessante, observando-se um aumento de seletividade de alguns CA funcionalizados para alguns dos fármacos em estudo, apesar da redução geral da SBET destes. Em suma, este trabalho demonstra o potencial das LP da indústria papeleira para a produção de CA alternativos aos CA comerciais, em particular para a formulação em pó, e para a sua aplicação na remoção de fármacos das águas.Programa Doutoral em Químic

Adsorção de fluoxetina a carvões de bio-resíduos ativados

Mestrado em Química - Química Analítica e QualidadeActivated carbons are one of the most promising techniques for the removal of organic and inorganic compounds from waters. In this work three activated carbons were produced using as precursor primary paper mill sludge. Chemical activation was performed using three different activation agents, KOH, NaOH and ZnCl2, and the same pyrolysis conditions were applied. The characterization of the obtained materials was made by means of total organic carbon analysis (TOC), Fourier infrared spectroscopy with attenuated total reflectance (FTIR-ATR), proximate and ultimate analysis, scanning electron microscopy (SEM), Hg porosimetry, BET isotherms and point of zero charge (PZC) determination. Adsorption studies were made, beginning with adsorption kinetic and then adsorption equilibrium (isotherms of adsorption), all performed in batch experiments. Generally, the carbons presented an equilibrium time of around six hours. Equilibrium studies allowed test the adsorption capacity of the produced carbons for fluoxetine-HCl. These two studies were also performed to the primary sludge pyrolysed under the same conditions without activation and also to a commercial activated carbon as reference. Among the produced materials, the carbon activated with ZnCl2 has the higher BET surface area and percentage of carbon. The maximum adsorption capacity (mg g-1) was of 96.2 ± 1.0 for PBFG4; 120.4 ± 2.5 for PS800-10; 191.6 ± 4.8 for PS800-10KOH; 136.6 ± 9.6 for PS800-10NaOH; and 28.4 ± 0.3 for PS800-10ZnCl2. The isotherms obtained point for different mechanism of adsorption between the carbons, probably due to their distinct PZC.Os carvões ativados são uma das técnicas mais promissoras para a remoção de compostos orgânicos e inorgânicos presentes nas águas. Neste trabalho, foram produzidos três carvões ativados utilizando como precursor lamas primárias residuais provenientes da produção de papel. Foi utilizada a ativação química com KOH, NaOH e ZnCl2, aplicando as mesmas condições de pirólise aos três carvões. A caracterização dos materiais obtidos foi feita por meio de análise de carbono orgânico total (TOC), espectroscopia de infravermelho com transformada de Fourier usando a técnica reflexão total atenuada (FTIR-ATR), Proximate and ultimate analysis, microscopia eletrónica de varrimento (SEM), porosimetria de mercúrio, isotérmicas BET e determinação do ponto de carga zero (PZC). Foram realizados estudos de adsorção iniciados pela cinética de adsorção e seguidos das isotérmicas, usando experiências em vaso fechado. Os estudos de cinética de adsorção mostraram que, na generalidade, todos os carvões produzidos apresentaram um tempo de equilíbrio semelhante, cerca de seis horas. As isotérmicas permitiram testar a capacidade de adsorção dos carvões produzidos para o composto fluoxetina-HCl. Estes dois estudos foram também aplicados à lama primária pirolisada sob as mesmas condições mas sem ativação e também a um carvão ativado comercial, usado como referência. Entre os materiais produzidos, o carvão ativado com ZnCl2 é o que apresenta uma área superficial específica (SBET) superior e maior percentagem de carbono. A capacidade máxima de adsorção (mg g-1) foi de 96.2 ± 1.0 para o PBFG4; 120.4 ± 2.5 para PS800-10; 191.6 ± 4.8 para PS800-10KOH; 136.6 ± 9.6 para PS800-10NaOH; e 28.4 ± 0.3 para PS800-10ZnCl2. As isotérmicas obtidas apontam para a existência de diferentes mecanismos de adsorção entre os carvões, provavelmente devido aos seus valores de PZC

Adsorption of pharmaceuticals from biologically treated municipal wastewater using paper mill sludge-based activated carbon

A waste-based alternative activated carbon (AAC) was produced from paper mill sludge under optimized conditions. Aiming its application in tertiary wastewater treatment, AAC was used for the removal of carbamazepine, sulfamethoxazole, and paroxetine from biologically treated municipal wastewater. Kinetic and equilibrium adsorption experiments were run under batch operation conditions. For comparison purposes, they were also performed in ultrapure water and using a high-performance commercial AC (CAC). Adsorption kinetics was fast for the three pharmaceuticals and similar onto AAC and CAC in either wastewater or ultrapure water. However, matrix effects were observed in the equilibrium results, being more remarkable for AAC. These effects were evidenced by Langmuir maximum adsorption capacities (qm, mg g-1): for AAC, the lowest and highest qm were 194 ± 10 (SMX) and 287 ± 9 (PAR), in ultrapure water, and 47 ± 1 (SMX) and 407 ± 14 (PAR), in wastewater, while for CAC, the lowest and highest qm were 118 ± 7 (SMX) and 190 ± 16 (PAR) in ultrapure water and 123 ± 5 (SMX) and 160 ± 7 (CBZ) in wastewater. It was found that the matrix pH played a key role in these differences by controlling the surface electrostatic interactions between pharmaceutical and AC. Overall, it was evidenced the need of adsorption results in real matrices and demonstrated that AAC is a promising option to be implemented in tertiary wastewater treatments for pharmaceuticals' removal. Graphical abstract Production of an alternative activated carbon (AC) comparing favourably with a commercial AC in the removal of neutral and positive pharmaceuticals from wastewater.publishe

Obtaining granular activated carbon from paper mill sludge: a challenge for application in the removal of pharmaceuticals from wastewater

In this work, a granular activated carbon (GAC) was produced using primary paper mill sludge (PS) as raw material and ammonium lignosulfonate (AL) as binder agent. PS is a residue from the pulp and paper industry and AL is a by-product of the cellulose pulp manufacture and the proposed production scheme contributes for their valorisation together with important savings in GAC precursors. The produced GAC (named PSA-PA) and a commercially available GAC (GACN), used as reference material, were physically and chemically characterized. Then, these materials were tested in batch experiments for the adsorption of carbamazepine (CBZ), sulfamethoxazole (SMX), and paroxetine (PAR) from ultra-pure water and wastewater. Even though GACN and PSA-PA possess very similar specific surface areas (SBET) (629 and 671 m2 g-1, respectively), PSA-PA displayed lower maximum adsorption capacities (qm) than GACN for the pharmaceuticals here studied (6 ± 1-44 ± 5 mg g-1 and 49 ± 6-106 ± 40 mg g-1, respectively). This may be related to the comparatively higher incidence of mesopores in GACN, which might have positively influenced its adsorptive performance. Moreover, the highest hydrophobic character and degree of aromaticity of GACN could also have contributed to its adsorption capacity. On the other hand, the performance of both GACs was significantly affected by the matrix in the case of CBZ and SMX, with lower qm in wastewater than in ultra-pure water. However, the adsorption of PAR was not affected by the matrix. Electrostatic interactions and pH effects might also have influenced the adsorption of the pharmaceutical compounds in wastewater.publishe

Fixed-bed performance of a waste-derived granular activated carbon for the removal of micropollutants from municipal wastewater

This work aimed to assess the fixed-bed adsorptive performance of a primary paper mill sludge-based granular activated carbon (PSA-PA) for the removal of pharmaceuticals, namely carbamazepine (CBZ), sulfamethoxazole (SMX) and paroxetine (PAR), from water. The breakthrough curves corresponding to the adsorption of CBZ at different flow rates and in two different matrices (distilled and urban wastewater) were firstly determined, which allowed to select the most favorable flow rate for the subsequent experiments. The fixed-bed adsorption of CBZ, SMX and PAR from single and ternary solutions in wastewater showed that the performance of PSA-PA was different for each pharmaceutical. According to the obtained breakthrough curves, the poorest bed adsorption capacity, either from single or ternary solution, was that for SMX, which may be related with electrostatic repulsion at the pH of the wastewater used (pH ~ 7.3–7.7). Also, the bed adsorption capacity of PSA-PA for SMX was notoriously lower in the ternary than in the single solution, while it slightly decreased for CBZ and even increased for PAR. The regeneration studies showed that the CBZ adsorption capacity of the PSA-PA bed decreased about 38 and 71% after the first and the second thermal regeneration stages, respectively. This decline was comparatively larger than the corresponding reduction of the PSA-PA specific surface area (SBET), which decreased only 5 and 25% for the first and second regeneration, respectively, and pointed to the lack of viability of more than one regeneration stage.publishe

Sludge from paper mill effluent treatment as raw material to produce carbon adsorbents: An alternative waste management strategy

Pulp and paper industry produces massive amounts of sludge from wastewater treatment, which constitute an enormous environmental challenge. A possible management option is the conversion of sludge into carbon-based adsorbents to be applied in water remediation. For such utilization it is important to investigate if sludge is a consistent raw material originating reproducible final materials (either over time or from different manufacturing processes), which is the main goal of this work. For that purpose, different primary (PS) and biological sludge (BS) batches from two factories with different operation modes were sampled and subjected to pyrolysis (P materials) and to pyrolysis followed by acid washing (PW materials). All the materials were characterized by proximate analysis, total organic carbon (TOC) and inorganic carbon (IC), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and N2 adsorption isotherms (specific surface area (SBET)and porosity determination). Sludge from the two factories proved to have distinct physicochemical properties, mainly in what concerns IC. After pyrolysis, the washing step was essential to reduce IC and to considerably increase SBET, yet with high impact in the final production yield. Among the materials here produced, PW materials from PS were those having the highest SBET values (387-488 m2 g-1). Overall, it was found that precursors from different factories might originate final materials with distinct characteristics, being essential to take into account this source of variability when considering paper mill sludge as a raw material. Nevertheless, for PS, low variability was found between batches, which points out to the reliability of such residues to be used as precursors of carbon adsorbents.L'Oreal Portugalpublishe

Waste-based alternative adsorbents for the remediation of pharmaceutical contaminated waters: Has a step forward already been taken?

When adsorption is considered for water treatment, commercial activated carbon is usually the chosen adsorbent for the removal of pollutants from the aqueous phase, particularly pharmaceuticals. In order to decrease costs and save natural resources, attempts have been made to use wastes as raw materials for the production of alternative carbon adsorbents. This approach intends to increase efficiency, cost-effectiveness, and also to propose an alternative and sustainable way for the valorization/management of residues. This review aims to provide an overview on waste-based adsorbents used on pharmaceuticals' adsorption. Experimental facts related to the adsorption behaviour of each adsorbent/pharmaceutical pair and some key factors were addressed. Also, research gaps that subsist in this research area, as well as future needs, were identified. Simultaneously, this review aims to clarify the current status of the research on pharmaceuticals' adsorption by waste-based adsorbents in order to recognize if the right direction is being taken.publishe

Core-shell molecularly imprinted polymers on magnetic yeast for the removal of sulfamethoxazole from water

In this work, magnetic yeast (MY) was produced through an in situ one-step method. Then, MY was used as the core and the antibiotic sulfamethoxazole (SMX) as the template to produce highly selective magnetic yeast-molecularly imprinted polymers (MY@MIPs). The physicochemical properties of MY@MIPs were assessed by Fourier-transform infrared spectroscopy (FT-IR), a vibrating sample magnetometer (VSM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), specific surface area (SBET) determination, and scanning electron microscopy (SEM). Batch adsorption experiments were carried out to compare MY@MIPs with MY and MY@NIPs (magnetic yeast-molecularly imprinted polymers without template), with MY@MIPs showing a better performance in the removal of SMX from water. Adsorption of SMX onto MY@MIPs was described by the pseudo-second-order kinetic model and the Langmuir isotherm, with maximum adsorption capacities of 77 and 24 mg g-1 from ultrapure and wastewater, respectively. Furthermore, MY@MIPs displayed a highly selective adsorption toward SMX in the presence of other pharmaceuticals, namely diclofenac (DCF) and carbamazepine (CBZ). Finally, regeneration experiments showed that SMX adsorption decreased 21 and 34% after the first and second regeneration cycles, respectively. This work demonstrates that MY@MIPs are promising sorbent materials for the selective removal of SMX from wastewater.publishe

Production of highly efficient activated carbons from industrial wastes for the removal of pharmaceuticals from water: a full factorial design

The wide occurrence of pharmaceuticals in aquatic environments urges the development of cost-effective solutions for their removal from water. In a circular economy context, primary paper mill sludge (PS) was used to produce activated carbon (AC) aiming the adsorptive removal of these contaminants. The use of low-cost precursors for the preparation of ACs capable of competing with commercial ACs continues to be a challenge. A full factorial design of four factors (pyrolysis temperature, residence time, precursor/activating agent ratio, and type of activating agent) at two levels was applied to the production of AC using PS as precursor. The responses analysed were the yield of production, percentage of adsorption for three pharmaceuticals (sulfamethoxazole, carbamazepine, and paroxetine), specific surface area (SBET), and total organic carbon (TOC). Statistical analysis was performed to evaluate influencing factors in the responses and to determine the most favourable production conditions. Four ACs presented very good responses, namely on the adsorption of the pharmaceuticals under study (average adsorption percentage around 78%, which is above that of commercial AC), and SBET between 1389 and 1627 m2 g-1. A desirability analysis pointed out 800 °C for 60 min and a precursor/KOH ratio of 1:1 (w/w) as the optimal production conditions.publishe

Single and multi-component adsorption of psychiatric pharmaceuticals onto alternative and commercial carbons

This work describes the adsorptive removal of three widely consumed psychiatric pharmaceuticals (carbamazepine, paroxetine and oxazepam) from ultrapure water. Two different adsorbents were used: a commercial activated carbon and a non-activated waste-based carbon (PS800-150-HCl), produced by pyrolysis of primary paper mill sludge. These adsorbents were used in single, binary and ternary batch experiments in order to determine the adsorption kinetics and equilibrium isotherms of the considered pharmaceuticals. For the three drugs and both carbons, the equilibrium was quickly attained (with maximum equilibrium times of 15 and 120 min for the waste-based and the commercial carbons, respectively) even in binary and ternary systems. Single component equilibrium data were adequately described by the Langmuir model, with the commercial carbon registering higher maximum adsorption capacities (between 272 ± 10 and 493 ± 12 μmol g-1) than PS800-150-HCl (between 64 ± 2 and 74 ± 1 μmol g-1). Multi-component equilibrium data were also best fitted by the single component Langmuir isotherm, followed by the Langmuir competitive model. Overall, competitive effects did not largely affect the performance of both adsorbents. Binary and ternary systems maintained fast kinetics, the individual maximum adsorption capacities were not lower than half of the single component systems and both carbons presented improved total adsorption capacities for multi-component solutions.publishe