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Dye effluents cause diverse environmental problems. Methylene blue (MB) dye stands out since it is widely used in the textile industry. To reduce the pollution caused by the MB, we developed biosorbents from tucumã seeds, where the in natura seeds were treated with NaOH (BT) and H3PO4 (AT) solutions and characterized by Boehm titration, point of zero charges, FTIR, TGA, BET, and SEM. It was observed that the acid groups predominate on the surface of the three biosorbents. The process was optimized for all biosorbents at pH = 8, 7.5 g/L, 240 min, C0 = 250 mg/L, and 45 ℃. BT was more efficient in removing MB (96.20%; QMax = 35.71 mg/g), while IT and AT removed around 60% in similar conditions. The adsorption process best fits Langmuir and Redlich-Peterson isotherms, indicating a hybrid adsorption process (monolayer and multilayer) and pseudo-second-order kinetics. Thermodynamic data confirmed an endothermic and spontaneous adsorption process, mainly for BT. MB was also recovered through a desorption process with ethanol, allowing the BT recycling and reapplication of the dye. Thus, an efficient and sustainable biosorbent was developed, contributing to reducing environmental impacts.

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This study aimed to assess the value of Pachira aquatica Aubl. fruit peels by exploring their applicability in the biosorption process for the removal of Ni(II) and Cd(II) metal ions. The Pachira aquatica Aubl. fruit peel biochar (PAB) was extensively characterized through various techniques, including proximate analysis, helium pycnometer, XRD, SEM, point of zero charge determination, zeta potential measurement, and Boehm titration. Subsequently, kinetic, isotherm, and thermodynamic batch biosorption studies were conducted, followed by column biosorption tests. The characteristics of PAB, including low moisture content, a neutral point of zero charge, porosity, an irregular and heterogeneous structure, a negatively charged surface, and the presence of functional groups, indicate its remarkable capacity for efficiently binding with heavy metals. Biosorption equilibrium time was achieved at 300 min for both ions, fitting well with a pseudo second-order kinetic model and Langmuir isotherm model. These data suggest that the biosorption process occurred chemically in monolayer. The column C presented an exhaust volume of 1200 mL for Ni(II) and 1080 for Cd(II) and removal of 98% and 99% of removal for Ni(II) and Cd(II), respectively. In summary, PAB demonstrates substantial potential as a biosorbent for effectively removing heavy metals, making a valuable contribution to the valorization of this co-product and the mitigation of environmental pollution.

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Vinasse and ash from sugarcane bagasse (SCB) are key byproducts in the sugar-energy industry. Vinasse is nutrient-rich but environmentally challenging, while sugarcane bagasse ash (SCBA) offers excellent adsorbent for treating effluents. This work aims to assess the effectiveness of SCBA in removing nitrogen (N) and potassium (K) nutrients from Vinasse. Simulated standard solutions of K2SO4 and (NH4)2HPO4 were used to mimic the nutrient concentrations in Vinasse and optimize experimental parameters such as adsorbent mass and contact time. Kinetic and isotherm models were also applied to elucidate the underlying adsorption mechanisms. Structural, morphological, and thermal analyses revealed the micro-mesoporous and heterogeneous nature of SCBA, primarily composed of SiO2 (quartz and cristobalite). The sorption assessment indicated the ideal conditions involved lower SCBA masses (2.5 g) and 6 h of contact time for the simulated standard solutions. The replicated conditions for Vinasse (at an adjusted sorption time of 24 h) demonstrated nutrient sorption and pH correction of the Vinasse, attributed to the alkaline nature of SCBA. Analysis of the sorption kinetic models for K+ and NH4+ revealed that SCBA interacts diffusively with the environment, not necessarily controlled by adsorption on active sites, indicating non-uniform characteristics. The sorption isotherms for K+ and NH4+ showed the non-linearized Freundlich model was the most suitable, indicating the adsorption sites with varying energy levels and a multilayer sorption process. In conclusion, we successfully demonstrated the sorption of nutrients from Vinasse by SCBA, enhancing the value of these residues and mitigating their environmental impact when used in agricultural applications.

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The presence of sertraline hydrochloride (SER) has been detected in water bodies and wastewater, which encourages the search for alternative treatments for its control and removal. Agro-industrial residues are considered efficient adsorbents and functionalization with magnetic nanoparticles improve the adsorptive properties of these materials, in addition to facilitating their separation from a fluid by an external magnetic field. Thus, this study developed and characterized a new material via the functionalization of the banana peel with iron oxide nanoparticles (BANFunc) for the adsorption of SER in batch experiments. Physicochemical and spectroscopic techniques indicated that the BANFunc functionalization method was effective and improved the adsorption capacity (0.68 and 39.96 mg g-1 for BANPure and BANFunc, respectively). The adsorption studies revealed a maximum adsorptive capacity of 142.85 mg g-1 at 240 min and 318 K. Furthermore, the process presented spontaneous and endothermic behaviour, with a better fit to the pseudo-first-order and Langmuir models for the kinetic and isothermal, respectively. The reuse of the biosorbent was effective for five cycles, and even in the 3rd cycle, the adsorbent showed more than 80% SER removal. The adsorption process can be explained by hydrogen bonds and π-interactions. In the synthetic mixture treatment, the biosorbent demonstrated a satisfactory removal rate, of 86.91%, and individual removals of 83.23%, 89.36% and 88.15% for SER, safranine orange and chloroquine, respectively. Therefore, BANFunc is a promising material for large-scale applications, considering its sustainable character and high treatment efficiency.

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Conventional textile effluent treatments cannot remove methylene blue, a mutagenic azo dye, and an endocrine disruptor, that remains in the drinking water after conventional water treatment. However, the spent substrate from Lentinus crinitus mushroom cultivation, a waste, could be an attractive alternative to remove persistent azo dyes in water. The objective of this study was to assess the methylene blue biosorption by spent substrate from L. crinitus mushroom cultivation. The spent substrate obtained after mushroom cultivation had been characterized by the point of zero charge, functional groups, thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. Moreover, the spent substrate biosorption capacity was determined in function of pH, time, and temperature. The spent substrate had a point of zero charge value of 4.3 and biosorbed 99% of methylene blue in pH from 3 to 9, with the highest biosorption in the kinetic assay of 15.92 mg g- 1, and in the isothermal assay of 120.31 mg g- 1. Biosorption reached equilibrium at 40 min after mixing and best fitted the pseudo-second-order model. Freundlich model best fitted the isothermal parameters and each 100 g spent substrate biosorbed 12 g dye in an aqueous solution. The spent substrate of L. crinitus cultivation is an effective biosorbent of methylene blue and an alternative to removing this dye from water, adding value to the mushroom production chain, and supporting the circular economy.

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Groundwater is one of the most important reservoirs in semi-arid and arid zones of the world, particularly in Mexico. The aims of this work were to produce a biosorbent from watermelon peel waste and a biosorbent with citric acid treatment and to evaluate both biosorbents with different concentrations of arsenic in groundwater. The biosorbents were produced with watermelon peel residues, which were observed by SEM microscopy to evaluate their physical morphology. Its removal potential was tested at concentrations of 0, 1, 13, 22, and 65 µg/L of arsenic, and both adsorption capacity and removal percentage were analyzed by final measurement obtained by atomic absorption spectrometry. The pH was measured throughout the experimentation maintaining ranges between 5.5 and 7.5. The biosorbent without treatment presented clearer and more compact flakes. At the microscopic level, the biosorbent without treatment presented pores with a more circular shape, and the biosorbent with treatment was more polygonal, similar to a honeycomb. The highest removal percentage was 99.99%, for both treatments at 4 h. The biosorbent without treatment at 4 h with arsenic concentrations of 65 µg/L presented the highest adsorption capacity (2.42 µg/g). It is concluded that watermelon peel biosorbent is a material that has the potential to remove arsenic from groundwater. This type of biosorbent is effective to remove arsenic and could be used in the field, however, it still needs to be optimized to convert it into a material completely suitable for large-scale use.

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The direct magnetic sorbent sampling flame atomic absorption spectrometry (DMSS-FAAS), recently proposed by our research group, was applied to determine the lead in soy-based juice, whole grape juice, reconstituted grape juice, and orange nectar samples. A dispersive solid phase extraction (d-SPE) of lead was carried out using a magnetic orange peel powder, developed and optimized by Gupta et al (2012), that was inserted into flame by FAAS with a magnetic probe. The limits of quantification (<4.6 µg L-1) were smaller than maximum residue limits established in Brazil. Good precisions and accuracies were obtained. DMSS-FAAS presented a sensitivity at least 14 times greater than the d-SPE followed by conventional FAAS analysis, wherein the analytes were extracted and desorbed, and the eluate was introduced in FAAS via nebulization system. Lead was easily quantified in juice samples at very low concentrations, with satisfactory figures of merit, and without the need of a mineralization step.

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The presence of micropollutants, such as caffeine (CAF), has been detected throughout the world, since conventional treatment plants are not able to properly degrade them. CAF is a widely consumed stimulant, and has been demanding the development of efficient methodologies for its removal. Aiming at the agriculture waste valorization, a new hydrochar was developed based on chemical and thermal modification of peach stones (mod-PS) for CAF removal from water and from a synthetic mixture. The morphology, functional groups and surface electrical charge of the adsorbent were characterized by SEM, FTIR and zeta potential, respectively. Regarding CAF adsorption performance, the equilibrium time was reached at 480 min and the pseudo-second-order model presented the best fit for the experimental data. The maximum adsorption capacity was 68.39 mg g-1 (298 K) and the Langmuir model exhibited a better fit for the isothermal data. The thermodynamic properties confirmed that the process was exothermic, spontaneous and reversible. The main adsorption mechanisms were hydrogen bonds and π-interactions. The global removal efficiency was satisfactory in the synthetic mixture simulating real wastewater (67%). Therefore, the proposed new hydrochar has potential application as a low-cost adsorbent for CAF removal.

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This research was carried out to examine the effects of Sargassum stolonifolium on reducing cadmium in Brassica chinensis L. tissue, its influential roles on physiological parameters and antioxidant mechanism in B. chinensis exposed to cadmium stress. Different levels of Cd (50 mg and 100 mg) with and without S. stolonifolium (25g, 50g and 100g) under five replications were explored in this study. Biomass, photosynthetic pigment, relative water content (RWC), malondialdehyde (MDA), hydrogen peroxide (H2O2), 2,2-diphenyl-1-picrylhydrazyl (DPPH), total antioxidant activity (TAA), non-protein thiol (NPT), protein thiol (PT), protein bound thiol, glutathione (GSH), phytochelatins, ascorbate peroxidase (APX), Catalase (CAT), superoxide dismutase (SOD) and guaiacol peroxidase (POD) were determined. The results revealed that Cd stress significantly (P < 0.05) reduced plant biomass and physiological attributes, and accumulated higher Cd concentrations in plant tissues with the increasing rate of Cd concentration in the soil. However, incorporation of S. stolonifolium at 100 g rate in 50 mg Cd (T4) spiked soil increased the FW (40.6%) and DW (72.2%) relative to the respective treatment without S. stolonifolium. Similarly, Cd accumulation in roots, stem and leaves was decreased by 90.25%, 82.93% and 84.6% respectively compared to T1 (50 mg Cd) and thereby reducing leaf MDA and H2O2 contents by 40.1% and 68.8%, respectively, at 50 mg Cd kg−1 spiked soil relative to T1. An increase was noticed in the chlorophyll a, b, carotenoid, SPAD and RWC with a value of 114.6%, 20.7%, 73.7%, 44.8%, and 6.3%, respectively, over the control (T0). DPPH scavenging activity and TAA increased 119.8 and 81.5% percent respectively over the T0. Concentration increment of NPT, TT, GSH and PCs by 66.7%, 49.1%, 60.1%, 96.1% and 3.4% respectively, was noticed in T4 compared to T0. Antioxidant enzymes activities increased by APX (92.8%), CAT (73.1%), SOD (20.9%) and POD (88.9%) for T4 compared to the control. S. stolonifolium has the potential to improve growth and increase the defensive system of B. chinensis and ameliorate cadmium phytotoxicity as well as immobilization.(AU)

Esta pesquisa foi realizada para examinar os efeitos de Sargassum stolonifolium na biossorção de cádmio em tecido de Brassica chinensis L., e a influência em parâmetros fisiológicos e antioxidantes em B. chinensis exposta ao estresse por cádmio. Foram avaliados níveis de Cd (50 mg e 100 mg), com ou sem S. stolonifolium (25g, 50g e 100g), em cinco repetições. Biomassa, pigmento fotossintético, teor relativo de água (RWC), malondialdeído (MDA), peróxido de hidrogênio (H2O2), 2,2-difenil-1-picrilhidrazil (DPPH), atividade antioxidante total (TAA), tiol não proteico (NPT), tiol proteico (PT), tiol ligado às proteínas, glutationa (GSH), fitoquelatinas, ascorbato peroxidase (APX), Catalase (CAT), superóxido dismutase (SOD) e guaiacol peroxidase (POD) foram determinados. Os resultados revelaram que o estresse por Cd reduziu significativamente (P < 0,05) a biomassa vegetal e os atributos fisiológicos, e acumulou maiores concentrações de Cd nos tecidos vegetais com o aumento da taxa de concentração de Cd no solo. No entanto, a incorporação de S. stolonifolium na dose de 100 g em solo aumentou a AF (40,6%) PD (72,2%) em relação ao respectivo tratamento sem S. stolonifolium. Da mesma forma, o acúmulo de Cd nas raízes, caule e folhas foi reduzido em 90,25%, 82,93% e 84,6%, respectivamente, comparando T1 e, assim, reduzindo os teores de MDA e H2O2 nas folhas em 40,1% e 68,8%, respectivamente, a 50 mg Cd kg−1 de solo enriquecido em relação a T0 e T1. Um aumento foi observado na clorofila a, b, carotenoide, SPAD e RWC de 114,6%, 20,7%, 73,7%, 44,8% e 6,3%, respectivamente, em relação ao controle. Aumento da concentração de NPT, TT, GSH e PCs em 66,7%, 49,1%, 60,1%, 96,1% e 3,4%, respectivamente, foi observado em T4 em relação a T0. As atividades das enzimas antioxidantes APX (92,8%), CAT (73,1%), SOD (20,9%) e POD (88,9%) aumentam em T4, em relação ao controle. S. stolonifolium tem potencial para promover o crescimento e aumentar o sistema de defesa de B. chinensis e reduzir os efeitos negativos da fitotoxicidade do cádmio, bem como a sua imobilização.(AU)

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The present work aims to evaluate the removal capacity of Rhodamine B dye (RhB) using nano-porous chitosan (NC) from shrimp shells. NC was characterized by XRD, SEM-EDS, N2 porosimetry, zeta potential (ZP), FTIR, DLS, and zero charge point (pHZCP). Compound central rotational design (CCRD) was used to determine the ideal condition and antimicrobial activity was evaluated against different strains. NC showed characteristic of semi-crystalline material with negative charge surface (around - 21.13 mV), and SBET = 1.12 m2 g-1, Vp = 0.0064 cm3 g-1, Dp = 32.09 nm and pHZCP ≈ 7.98. Kinetic adsorption showed the pseudo first-order model had the best fit, with adsorption capacity (q1) between 3.78 and 64.43 mg g-1 and pseudo first-order kinetic constant (k1) between 0.066 and 0.052 min-1. Sips model best described the equilibrium data, with a maximum adsorption capacity of 505.131 mg g-1. Antimicrobial activity was observed at 0.25 mg mL-1 for different strains. Therefore, NC has potential application in the removal of the dye, combining sustainable development associated with nanotechnology.

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Safranin orange (SO) is a cationic dye widely used in industrial sectors. It becomes a threat to the aquatic ecosystem once it reaches water resources, directly affecting photosynthetic activity and dissolved oxygen rate. In view of this scenario and considering the large production of agro-industrial waste, which provides significant disposal costs and environmental impacts, the agricultural by-products such as mandarin peels (MP) are being used as biosorbent materials. Thus, this work proposed the use of MP for SO adsorption. The material was characterized by SEM, zeta potential, and FTIR analysis, in which it was possible to verify heterogeneous porous morphology, predominantly negative surface, and organic functional groups that facilitate adsorption. The results were promising, wherein the maximum adsorption capacity was 464 mg g-1 (318 K), 0.4 g L-1 adsorbent concentration, 120 min equilibrium time and removal percentage of 84.75%. The experimental data showed a better fit to the Langmuir and pseudo-second order mathematical models. The thermodynamic analysis inferred spontaneous, endothermic, and reversible character for SO adsorption onto MP. The main proposed adsorptive mechanisms were hydrogen bonds, π-interactions, and electrostatic interactions. In addition, the reuse of MP showed good efficiency since the adsorption capacity was maintained above 50% after four cycles (from 77.90 to 41.55 mg g-1). Moreover, when evaluating the effect of pH and ionic strength, it verified that the adsorption efficiency was not reduced. Therefore, when compared with other materials, the versatility and potential applicability of MP as a low-cost adsorbent for wastewater treatment is notable.

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In this study, urban pruning waste biosorbent after thermal activation process was used to remove zinc ion from aqueous solution. The zinc adsorption was fast, with values above 98.0% removal after 5 min. The maximum removal achieved was 99.4% in 360 min, at 30°C, pH 5.0, and initial zinc concentration of 10 mg L-1. The adsorption process was adequately described by the pseudo-second-order kinetic model (R2 = 1.000), and data obtained from batch adsorption experiments fitted well with the Langmuir isotherm model. The maximum adsorption capacity of zinc onto urban pruning waste biosorbent was 18.382 mg g-1 at 30°C. Thus, it is concluded that urban pruning waste can be used as a low-cost alternative biosorbent to remove zinc in aqueous solutions.

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In this study, a biosorbent material with characteristics for the adsorption of organic compounds was used for a cork pellet-based bar adsorptive microextraction technique, as a new greener alternative for the determination of organochlorine compounds. Aldrin, chlordane, dieldrin, endrin, lindane, 4,4-DDD, 4,4-DDE, 4,4-DDT, α-endosulfan and ß-endosulfan were analyzed in water samples (drinking water, stream water and river water) with separation/detection by gas chromatography and electron capture detection (GC/ECD). The parameters that can affect the sample preparation efficiency such as desorption solvent and time as well as extraction time and ionic strength were evaluated by multivariate and univariate designs. Cork pellets (10  ×  Ø 3 mm) were used for the extraction of 15 mL of sample in the optimal conditions: 60 min of agitation with no salt added to the sample, followed by desorption of the cork pellet with 120 µL of ethyl acetate for 30 min. The bar-to-bar RSD out with five different bars showed good results with RSD ≤ 15.6%, allowing the use of simultaneous extractions. LOD and LOQ values ranged from 3 to 15 ng L-1 and 10 to 50 ng L-1 respectively, and the determination coefficients were greater than 0.9869. The target analytes were not detected in the three analyzed samples. Therefore, the recovery study was performed fortifying the water samples. Analyte recovery ranged from 48.7 - 138.2% for drinking water, 40.2 - 128.2% for stream water and 67.5 - 128.7% for river water.

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In this review, bibliometric analysis was made of recent studies and current trends concerning the application of lignocellulosic materials as bioadsorbents for the removal of arsenic from aqueous systems. Evaluation was made of lignocellulosic adsorbents and their chemical characteristics, as well as interactions involved in the adsorption of arsenic, bioadsorbent reusage (desorption and re-adsorption), competition between co-existing ions in multi-element aqueous solutions, and applications of bioadsorbents in batch and continuous systems. Lignocellulosic biomass has been shown to be a promising source of new adsorbents, since it is a low-cost and renewable material. However, there seems to be no commercially available technology that uses bioadsorbents based on lignocellulosic biomass for arsenic removal. In addition, the structural modification of lignocellulosic biomass to improve its adsorption capacity and selectivity has proved to be a suitable strategy, with the service time and the selectivity of the bioadsorbent in the presence of co-existing ions the most critical aspects to be pursued. The competitive adsorption of co-existing anions (PO43-, SO42-, NO3-, and Cl-) by the adsorption sites, as well as life-cycle assessment and cost analysis are rarely reported. Complexation, electrostatic attraction, ion exchange and precipitation were the main interactions involved in the adsorption of arsenic on lignocellulosic materials. However, most studies have failed to prove the nature of the interactions. Macroscopic methods can be useful to evaluate the adsorption mechanism of arsenic on bioadsorbents of complex structure, such as lignocellulosic biomass (modified or not). Nevertheless, the elucidation of the adsorption mechanism requires experiments based on measurements at the microscopic level. The upscaling of biosorption technology for arsenic removal will only be possible through studies that investigate: i) the interactions involved in the adsorption process; ii) the transfer of bench-scale experiments to pilot-scale experiments with real contaminated water with low arsenic concentration; and iii) the life-cycle assessment of biosorbents produced from lignocellulosic biomass.

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Eutrophication is one of the environmental problems arising from the increase of essential nutrient concentrations, mainly phosphorus and nitrogen. In contrast to excess phosphorus, the depletion of phosphate rock deposits used for the production of fertilizers compromises the food supply. Therefore, the development of technologies that propose the recovery of the phosphorus contained in eutrophic environments for its later use for agricultural fertilization purposes is very important to ensure global food security. This work aimed to evaluate the toxic potential of the sawdust (biosorbent previously used for phosphorus adsorption) in order to enable its application in agriculture. For this, toxicity experiments with Lactuca sativa (lettuce) and Allium cepa (onion) seeds were performed. The phytotoxic potential was assessed by means of the seed germination index and physiological parameters such as radicle and hypocotyl growth. Cytotoxicity, genotoxicity, and mutagenicity tests were also performed on onion seeds. From statistical tests, it was possible to affirm that the sawdust did not promote inhibition of seed germination and radicle and hypocotyl growth. No genotoxicity, cytotoxicity and, mutagenicity were observed, which allowed to state that the sawdust is not toxic to the onion species, which reinforces the possibility of application of the biosorbent for soil fertilization purposes. Therefore, the use of sawdust for phosphorus biosorption with the subsequent agricultural application is promising and quite important from a global food security point of view.

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This study investigates, for the first time, the applicability of seed pods from Capparis flexuosa as an alternative biosorbent to remove methylene blue and bright blue from aqueous medium using continuous and batch systems. The biosorbent was characterized by different techniques, whose particles presented rough surface and large pores and functional groups existing on its surface. In the batch system, an adsorptive capacity of 96.40 mg g-1 and 80% of methylene blue removal was reached with 0.9 g L-1 of adsorbent at pH 10, whereas 109.7 mg g-1 and 83% of bright blue removal was observed using 0.8 g L-1 of adsorbent at pH 2.0. The Elovich model adjusted the experimental data satisfactorily for both dyes. Tóth model for the MB best described the equilibrium data, and the Langmuir model for the bright blue both favored by the increase of temperature and dyes' concentration. The maximum capacities obtained were 280.78 mg g-1 and 342.85 mg g-1 for methylene blue and bright blue, respectively. The thermodynamic parameters indicated spontaneous processes, with endothermic behavior for both dyes. The fixed adsorption experiments using Capparis flexuosa seed pods showed adsorptive capacities of 158.65 and 205.81 mg g-1 for the methylene blue and bright blue, respectively. The overall results indicated that the pods of the Capparis flexuosa could be an ecological, effective, and economical alternative in the removal of dyes for both continuous and batch systems.

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Diverse fields of modern environmental technology are nowadays focused on the discovery and development of new sources for oil spill removal. An especially interesting type of sorbents is those of natural origin-biosorbents-as ready-to-use constructs with biodegradable, nontoxic, renewable and cost-efficient properties. Moreover, the growing problem of microplastic-related contamination in the oceans further encourages the use of biosorbents. Here, for the first time, naturally pre-designed molting cuticles of the Theraphosidae spider Avicularia sp. "Peru purple", as part of constituting a large-scale spider origin waste material, were used for efficient sorption of crude oil. Compared with currently used materials, the proposed biosorbent of spider cuticular origin demonstrates excellent ability to remain on the water surface for a long time. In this study the morphology and hydrophobic features of Theraphosidae cuticle are investigated for the first time. The unique surface morphology and very low surface free energy (4.47 ± 0.08 mN/m) give the cuticle-based, tube-like, porous biosorbent excellent oleophilic-hydrophobic properties. The crude oil sorption capacities of A. sp. "Peru purple" molt structures in sea water, distilled water and fresh water were measured at 12.6 g/g, 15.8 g/g and 16.6 g/g respectively. These results indicate that this biomaterial is more efficient than such currently used fibrous sorbents as human hairs or chicken feathers. Four cycles of desorption were performed and confirmed the reusability of the proposed biosorbent. We suggest that the oil adsorption mechanism is related to the brush-like and microporous structure of the tubular spider molting cuticles and may also involve interaction between the cuticular wax layers and crude oil.

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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.

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A wide range of anthropogenic activities have caused various problems to the aquatic environment, leading to economic, social, and environmental losses. The use of materials for the recovery of water quality is very important due to the water scarcity scenario present in different parts of the world. The use of sawdust as an organic adsorbent for P removal in eutrophic environments attempts to address both water quality preservation and possible application of the organic adsorbent as fertilizer for agricultural practices. This use will result in important contributions to the water and food security. In this work, we performed laboratory experiments to study P adsorption and to evaluate possible adsorption of metals and emerging contaminants by sawdust. The experiments were carried out in 36 microcosms (glass jars), using 50% of the flasks as treatments (containing bags with sawdust) and the rest of the flasks as control (water and sediment without sawdust). For future application of sawdust as a fertilizer it is important to be aware of the presence of possible pathogenic microorganisms, thus the presence of helminth eggs was determined in the sawdust. The results showed the tendency of P adsorption by the biosorbent; maximum adsorption occurred at 214 d (41 µg P g-1 ), after the P desorption occurred. No helminth eggs or emerging contaminants and toxic metal were detected in the sawdust after its use as biosorbent, providing an important subsidy regarding the use of the biosorbent as soil fertilizer. Integr Environ Assess Manag 2019;00:1-12. © 2019 SETAC.

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The aim of this study was to determine the Cd2+ removal capacity of a biosorbent system formed by Saccharomyces cerevisiae in calcium alginate beads. The adsorption of Cd2+ by a S. cerevisiae-alginate system was tested either by batch or fixed-bed column experiments. The S. cerevisiae-alginate system was characterized using dynamic light scattering (DLS, zeta potential), size, hardness, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy. Beads of the S. cerevisiae-alginate system showed a spherical-elliptical morphology, diameter of 1.62 ± 0.02 mm, 96% moisture, negative surface charge (-29.3 ± 2.57 mV), and texture stability during storage at 4 °C for 20 days. In batch conditions, the system adsorbed 4.3 µg of Cd2+/g of yeast-alginate beads, using a Cd2+ initial concentration of 5 mg/L. Adsorption capacity increased to 15.4 µg/g in a fixed-bed column system, removing 83% of total Cd2+. In conclusion, the yeast-alginate system is an efficient option for the removal of cadmium at low concentrations in drinking water.