Adsorption of the First-Line Covid Treatment Analgesic onto Activated Carbon from Residual Pods of Erythrina Speciosa.

In this study, the residual pods of the forest species Erythrina speciosa were carbonized with ZnCl2 to obtain porous activated carbon and investigated for the adsorptive removal of the drug paracetamol (PCM) from water. The PCM adsorption onto activated carbon is favored at acidic solution pH. The isothermal studies confirmed that increasing the temperature from 298 to 328 K decreased the adsorption capacity from 65 mg g-1 to 50.4 mg g-1 (C0 = 175 mg L-1). The Freundlich model showed a better fit of the equilibrium isotherms. Thermodynamic studies confirmed the exothermic nature (ΔH0 = -39.1066 kJ mol-1). Kinetic data indicates that the external mass transfer occurs in the first minutes followed by the surface diffusion, considering that the linear driving force model described the experimental data. The application of the material in the treatment of a simulated effluent with natural conditions was promising, presenting a removal of 76.45%. Therefore, it can be concluded that the application of residual pods of the forest species Erythrina speciosa carbonized with ZnCl2 is highly efficient in the removal of the drug paracetamol and also in mixtures containing other pharmaceutical substances.

Application of biowaste generated by the production chain of pitaya fruit (Hylocereus undatus) as an efficient adsorbent for removal of naproxen in water.

Pharmaceutical compounds are a serious problem in the environment. They cause damage to the aquatic, animal, and human organisms and soon became considered emerging pollutants where their removal is extremely urgent. Among the techniques used, adsorption has been used with success, where several adsorbent materials, including those from residual biomass, have been used to remove these pollutants. In this study, the skins of the pitaya fruit (Hylocereus undatus) productive chain were carbonized with ZnCl2 to obtain activated carbon and later used in the adsorption of the drug naproxen (NPX) in a batch system. The Freundlich model demonstrated a better adjustment for the equilibrium isotherms. A high adsorption capacity for NPX (158.81 mg g-1) was obtained at 328 K, which can be attributed to the remarkable textural properties of the adsorbent, besides certain functional groups present on its surface. Thermodynamic studies confirmed the endothermic nature of the adsorption process (∆H0 = 0.2898 kJ mol-1). The linear driving force model (LDF) presented a good statistical adjustment to the experimental kinetic data. The application of the material in the treatment of simulated wastewater composed of various pharmaceutical drugs and salts was very promising, reaching 75.7% removal. Therefore, it can be inferred that the application of activated carbon derived from pitaya bark is highly promising in removing the NPX drug and treating synthetic mixtures containing other pharmaceutical substances.

Development of activated carbon from Schizolobium parahyba (guapuruvu) residues employed for the removal of ketoprofen.

Schizolobium parahyba species can be found in all of South America, producing several residues that can be a major opportunity to develop activated carbon. This work presents the investigation regarding the development of a high specific surface activated carbon (981.55 m2 g-1) and its application in the adsorption of ketoprofen from the aqueous media. The ketoprofen molecules were better adhered to the adsorbent surface under acidic conditions (pH = 2), being the ideal adsorbent dosage determined as 0.7 g L-1, resulting in satisfactory values. It was found that the system reached equilibrium in 200 to 250 min depending on the initial concentration studied, achieving an adsorption capacity of 229 mg g-1. The general order was the most suitable model for describing the experimental data, with an R2 ≥ 0.9985 and MSR ≤ 63.40 (mg g-1)2. The equilibrium adsorption found that the temperature increases the adsorption capacity, achieving 447.35 mg g-1 at 328 K. Besides that, the Tóth model was the most suitable for describing the isotherms R2 ≥ 0.9990 and MSR ≤ 25.67 (mg g-1)2, indicating a heterogeneous adsorbent. The thermodynamic values found that the adsorption of ketoprofen is spontaneous (average ΔG0 of - 32.79 kJ mol-1) and endothermic (ΔH0 10.44 kJ mol-1). The treatment of simulated effluent with the developed adsorbent was efficient, removing 90% of ketoprofen, ibuprofen, and salts. It was found that the adsorbent is reaming its adsorption capacity up to the 5th cycle, progressively decreasing the adsorption capacity until the adsorption does not occur past the 12th cycle. Overall, the results demonstrated that the activated carbon from residual biomass of the Schizolobium parahyba species could be an excellent alternative in obtaining an effective adsorbent to treat wastewater-containing drugs.

Woody residues of the grape production chain as an alternative precursor of high porous activated carbon with remarkable performance for naproxen uptake from water.

Activated carbon prepared from grape branches was used as a remarkable adsorbent to uptake naproxen and treat a synthetic mixture from aqueous solutions. The material presented a highly porous texture, a surface area of 938 m2 g-1, and certain functional groups, which were key factors to uptake naproxen from effluents. The maximum adsorption capacity predicted by the Langmuir model for naproxen was 176 mg g-1. The thermodynamic study revealed that the adsorption process was endothermic and spontaneous. The linear driving force (LDF) model presented a good statistical adjustment to the experimental decay data. A suitable interaction pathway of naproxen adsorption onto activated carbon was proposed. The adsorbent material was highly efficient to treat a synthetic mixture containing several drugs and salts, reaching 95.63% removal. Last, it was found that the adsorbent can be regenerated up to 7 times using an HCl solution. Overall, the results proved that the activated carbon derived from grape branches could be an effective and sustainable adsorbent to treat wastewaters containing drugs.

Adsorption investigation of 2,4-D herbicide on acid-treated peanut (Arachis hypogaea) skins.

In this work, peanut (Arachis hypogaea) skin, a by-product generated by the agricultural production of its seeds, was employed as a precursor in the preparation of an adsorbent for the 2,4-D removal in water. The skins were treated with sulfuric acid and characterized by different techniques. The adsorption was favored at acid pH = 2 with pHpzc = 6. The dosage of 0.9 g L-1 was considered ideal, obtaining satisfactory indications of removal and capacity. The kinetic curves were well represented by the general order model, with the equilibrium reached quickly in the first 30 min for all concentrations. Adsorption isotherm studies showed that the increase in temperature negatively affected the herbicide adsorption, obtaining a maximum capacity of 246.72 mg g-1, by the Langmuir isotherm at 298 K. The remarkable adsorption efficiency presented by the adsorbent can be associated with the presence of new functional groups on the adsorbent surface generated after the acid treatment. Thermodynamic parameters confirmed the exothermic nature of the adsorptive system. In the treatment of synthetic wastewater consisting of a mixture of herbicides and salts, a high removal efficiency (72%) of herbicides was obtained. Therefore, the development of an adsorbent derived from peanut (Arachis hypogaea) skin treated with sulfuric acid is an excellent alternative, generating remarkable removal results towards 2,4-D herbicide.

Transforming pods of the species Capparis flexuosa into effective biosorbent to remove blue methylene and bright blue in discontinuous and continuous systems.

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.

Successful adsorption of bright blue and methylene blue on modified pods of Caesalpinia echinata in discontinuous system.

Pods of the forest species Caesalpinia echinata were used as an alternative adsorbent to remove bright blue (BB) and methylene blue (MB) dyes. The raw and acid-treated samples were characterized by techniques like SEM, XRD, and FTIR. The acid-treated pod sample was characterized by an amorphous structure containing several cavities, bumps, and functional groups. The Elovich model was the most satisfactory to describe the adsorption kinetic data. The isothermal studies were better described by the Langmuir model for BB dye, with a maximum capacity of 261 mg g-1, and Tóth model for MB dye, giving a maximum capacity of 288 mg g-1. The thermodynamic study indicated a spontaneous and favorable process and endothermic nature for both dyes. In the treatment of two simulated effluents containing a mixture of different compounds such as dyes and salts, to simulate real wastewaters, the adsorbent was highly efficient, presenting around 80% of color removal for both effluents. Therefore, the acid-treated pods of Caesalpinia echinata have great potential to be applied as an alternative adsorbents in treating colored effluents in discontinuous systems.

Adsorption and mass transfer studies of methylene blue onto comminuted seedpods from Luehea divaricata and Inga laurina.

In this work, comminuted seedpods of the forest species Luehea divaricata (LDPR) and Inga laurina (ILPR) were used as alternative and environmental-friendly adsorbents for the methylene blue (MB) removal from aqueous solutions. Batch adsorption experiments were carried out at the native pH of the solution (pH = 8.7), with curves of removal and adsorption capacity crossed at 0.75 g L-1, having 125 mg g-1 for LDPR and 115 mg g-1 for ILPR. The kinetic models of pseudo-first-order (PFO) and HSDM-Crank were the most adequate to represent MB dye concentration decay data for both biosorbents. The equilibrium curves were better adjusted by the Langmuir model for both adsorbents, with maximum adsorption capacity increased from 279 to 325 mg g-1 for LDPR, and 199 to 233 mg g-1 for ILPR, as a function of an increase in temperature from 298 to 328 K. The thermodynamic parameters showed that both systems are spontaneous with a dominance of physisorption. Mass transfer analysis indicates that the external mass transfer is the limiting step, with Bi < 0.5. Surface diffusion increased with the adsorption capacity, presenting linear and exponential behavior for the ILPR and PLPR adsorbents, respectively. Both materials proved to be efficient in treating a simulated effluent with similar industrial wastewater characteristics, reaching superior values at 70% of color removal.

Potential of Cedrella fissilis bark as an adsorbent for the removal of red 97 dye from aqueous effluents.

Cedar bark (Cedrella fissilis), a waste from wood processing, was evaluated as an adsorbent for the removal of red 97 dye from effluents. The material exhibited an amorphous structure, irregular surface, and was mainly composed of lignin and holocellulose. The adsorption was favored at pH 2.0. The general order model was most suitable for describing the experimental kinetic data, being the equilibrium reached in around 30 min. The isotherm experiments were better described by the Langmuir model. The maximum adsorption capacity was 422.87 mg g-1 at 328 K. The values of standard Gibbs free energy change (ΔG0) were from - 21 to - 26 kJ mol-1, indicating a spontaneous and favorable process. The enthalpy change (ΔH0) was 18.98 kJ mol-1, indicating an endothermic process. From the fixed bed adsorption experiment, an inclined breakthrough curve was found, with a mass transfer zone of 5.36 cm and a breakthrough time of 329 min. Cedar bark was able to treat a simulated effluent attaining color removal of 86.6%. These findings indicated that cedar bark has the potential to be applied as a low-cost adsorbent for the treatment of colored effluents in batch and continuous adsorption systems.