Packed bed column adsorption of phenol onto corn cob activated carbon: linear and nonlinear kinetics modeling

Araucaria gum embedded kaolinite/ferric xanthan composite for enhanced adsorption of atrazine: Kinetic, thermodynamic, and column studies

Herbicides contribute significantly to water contamination, causing serious environmental and public health problems. The current study considers the creation of three adsorbents, ferric xanthan beads (X), ferric xanthan gum/kaolinite composite (KX), and xanthan gum/kaolinite modified with Araucaria gum (AKX), as powerful adsorbents for atrazine eradication from aqueous medium. Modern analytical tools were employed to characterize the fabricated adsorbents, which demonstrated that AKX has acceptable surface area (14.44 m2/g), with mesopores structure. The fabricated adsorbents were applied in a static adsorption procedure to remove atrazine, with varying parameters. Meanwhile, the column adsorption process focuses on the influence of bed height on atrazine removal by AKX. The results from the batch adsorption showed that AKX reached a maximum adsorption capacity (284.8 mg/g). The batch adsorption of atrazine was effectively modeled by the pseudo-first order, Elovich, Langmuir, and Temkin models for all the adsorbents. Thermodynamic studies revealed that the atrazine adsorption process is exothermic, physical, and occur spontaneously. The desorption efficiency for (X, KX, and AKX) reduced by only 15.9, 5.1, and 3.0 %, respectively, after 10 rounds of adsorption-desorption. Yoon-Nelson and Thomas models effectively applied breakthrough curves for atrazine column adsorption. AKX achieved a maximum column adsorption capacity of 384.0 mg/g under conditions of 20 mL/min flow rate, 1.5 cm bed height, and 80 mg/L initial atrazine concentration.

Column-based removal of high concentration microplastics in synthetic wastewater using granular activated carbon

Microplastic (MP) is an emerging contaminant of concern due to its abundance in the environment. Wastewater treatment plant (WWTP) can be considered as one of the main sources of microplastics in freshwater due to its inefficiency in the complete removal of small MPs. In this study, a column-based MP removal which could serve as a tertiary treatment in WWTPs is evaluated using granular activated carbon (GAC) as adsorbent/filter media, eliminating clogging problems commonly caused by powder form activated carbon (PAC). The GAC is characterized via N2 adsorption-desorption isotherm, field emission scanning electron microscopy, and contact angle measurement to determine the influence of its properties on MP removal efficiency. MPs (40-48 μm) removal up to 95.5% was observed with 0.2 g/L MP, which is the lowest concentration tested in this work, but still higher than commonly used MP concentration in other studies. The performance is reduced with further increase in MP concentration (up to 1.0 g/L), but increasing the GAC bed length from 7.5 to 17.5 cm could lead to better removal efficiencies. MP particles are immobilized by the GAC predominantly by filtration process by being entangled with small GAC particles/chips or stuck between the GAC particles. MPs are insignificantly removed by adsorption process through entrapment in GAC porous structure or attachment onto the GAC surface.

Synergistic mechanisms for the superior sorptive removal of aquatic pollutants via functionalized biochar-clay composite

This study investigated the successful synthesis of functionalized algal biochar-clay composite (FBKC). Subsequently, the sorption performance of FBKC towards norfloxacin (NFX) antibiotic and crystal violet dye (CVD) from water was extensively assessed in both batch and continuous flow systems. A series of characterization techniques were carried out for FBKC and the utilized precursors, indicating that the surface area of FBKC was increased thirty-fold with a well-developed pore structure compared to the original precursors. FBKC demonstrated a maximum sorption capacity of 192.80 and 281.24 mg/g for NFX and CVD, respectively. The suited fitting of the experimental data to Freundlich and Clark models suggested multi-layer sorption of NFX/CVD molecules. The mechanistic studies of NFX/CVD sorption onto FBKC unveiled multiple mechanisms, including π-π interaction, hydrogen bonding, electrostatic attraction, and surface/pore filling effect. The estimated cost of 5.72 €/kg and superior sorption capacity makes FBKC an efficient low-cost sorbent for emergent water pollutants.

Optimal pretreatment of plantain peel waste valorization for biogas production: Insights into neural network modeling and kinetic analysis

This work proposed a model for the substrate treatment stage of biogas production process in an anaerobic digestion system. Adaptive neuro-fuzzy inference system (ANFIS), response surface method (RSM), and artificial neural network (ANN) were comparatively used in the simulation and modeling of the treatment process for improved biogas yield. Waste plantain peels were pretreated and used as substrate. FTIR and SEM results revealed that the pretreatment improved the substrate's desirable qualities. The amount of biogas yield was controlled by time, NaOH concentration, and temperature of the substrate pretreatment. Optimum pretreatment conditions obtained were a temperature of 102.7 °C, time of 31.7 min and NaOH concentration of 0.125 N. RSM, ANN, and ANFIS modeling techniques were proficient in simulating the biogas production, as evidenced by high R2values of 0.9281, 0.9850, and 0.9852, respectively. Furthermore, the values of the calculated error terms such as RMSE (RSM = 0.04799, ANN = 0.00969, and ANFIS = 0.00587) and HYBRID (RSM = 18.556, ANN = 0.803, and ANFIS = 0.0447) were low, indicating a satisfactory correlation between experimental and predicted values. Scrubbing of the biogas with caustic soda and activated charcoal increased the methane content to 94 %. The kinetics of the cumulative biogas yield were best fit with the Logistics and Modified Logistics models. The low C/N ratio in addition to the presence of potassium, nitrogen, and phosphorus suggested that the spent plantain peel slurry can be utilized as an agricultural fertilizer in crop production. The observations of this study therefore recommends the pre-treatment of biodigestion substrates as a key means to enhance beneficiation of methane production.

Dynamic adsorption of 4-nitrophenol over shaped activated carbon produced from agriculture stones through microwave-assisted technique

The aim of current work is to develop the uptake of 4-nitrophenol from the liquid phase in a dynamic system by the shaped activated carbon produced through the microwave-assisted technique. The emphasis of research is to understand the effects of production factors on the performance of adsorbents in the dynamic adsorption. Hence, the phosphoric acid ratio, microwave irradiation power, carbonization temperature, and time were changed to identify the suitable conditions for the fabrication of granular and rod-like beds from the cherry, and date stones. It was found that the stone structure and H3PO4/waste ratio significantly affect the adsorption efficiency. The proper acid/waste ratio was determined to be 1.43, and 1.80 for the activation of cherry and date stones to achieve the maximal efficiency in which the power should be fixed at the levels of 600 and 400 W respectively. The equilibrium efficiency increases with the rise in carbonization temperature and time which should be controlled exactly to reach the maximal adsorption capacity, ~ 45 mg g-1 according to the Langmuir isotherm. Owing to the high specific surface area of shaped adsorbents, 350-450 mg g-1, the fabricated beds indicated the appropriate performance for the uptake of nitrophenol due to development of micropores, < 2 nm, in the framework of activated carbon.

Activated carbon prepared from Brazil nut shells towards phenol removal from aqueous solutions

The Brazil nut shell was used as a precursor material for preparing activated carbon by chemical activation with potassium hydroxide. The obtained material (BNSAC) was characterized, and the adsorptive features of phenol were investigated. The characterization showed that the activated carbon presented several rounded cavities along the surface, with a specific surface area of 332 m2 g-1. Concerning phenol adsorption, it was favored using an adsorbent dosage of 0.75 g L-1 and pH 6. The kinetic investigation revealed that the system approached the equilibrium in around 180 min, and the Elovich model represented the kinetic curves. The Sips model well represented the equilibrium isotherms. In addition, the increase in temperature from 25 to 55 °C favored the phenol adsorption, increasing the maximum adsorption capacity value (qs) from 83 to 99 mg g-1. According to the estimated thermodynamic parameters, the adsorption was spontaneous, favorable, endothermic, and governed by physical interactions. Therefore, the Brazil nut shell proved a good precursor material for preparing efficient activated carbon for phenol removal.

Sustainable functionalized smectitic clay-based nano hydrated zirconium oxides for enhanced levofloxacin sorption from aqueous medium

In this study, the functionalized smectitic clay (SC)-based nanoscale hydrated zirconium oxide (ZrO-SC) was successfully synthesized and utilized for the adsorptive removal of levofloxacin (LVN) from an aqueous medium. The synthesized ZrO-SC and its precursors (SC and hydrated zirconium oxide (ZrO(OH)₂)) were extensively characterized using various analytical methods to get insight into their physicochemical properties. The results of stability investigation confirmed that ZrO-SC composite is chemically stable in strongly acidic medium. The surface measurements revealed that ZrO impregnation to SC resulted in an increased surface area (six-fold higher than SC). The maximum sorption capacity of ZrO-SC for LVN was 356.98 and 68.87 mg g^-1 during batch and continuous flow mode studies, respectively. The mechanistic studies of LVN sorption onto ZrO-SC revealed that various sorption mechanisms, such as interlayer complexation, π-π interaction, electrostatic interaction, and surface complexation were involved. The kinetic studies of ZrO-SC in the continuous-flow mode indicated the better applicability of Thomas model. However, the good fitting of Clark model suggested the multi-layer sorption of LVN. The cost estimation of the studied sorbents was also assessed. The obtained results indicate that ZrO-SC is capable of removing LVN and other emergent pollutants from water at a reasonable cost.

Alternative activated/KOH adsorbent for phenol adsorption: experimental, industrial case study and mass transfer interpretation

Removal of phenol from wastewater is essential to achieve permitted concentrations according to the recommendations of USEPA. The adsorption capacity of phenol in activated adsorbent with KOH of Enterolobium contortisiliquum (TAC) was evaluated at different temperatures. The Langmuir isotherm represented the equilibrium data of this study. Thermodynamic process was endothermic, spontaneous, and reversible. The mass transfer parameters ranged from K_E 0.68 to 0.96 × 10^-3 (cm s^-1), Ds 8.95 to 14.35 × 10^-9 (cm² s^-1), and Dp 5.023 × 10^-8 (cm² s^-1). The PVSDM model represented the adsorption kinetics. Intraparticle diffusion limits the mass transfer process Biot > 100. The two-stage process minimized the total amount of TAC required to achieve the permitted specification of phenol concentration in wastewater from different industrial sectors. TAC showed significant performance in the removal of phenol from wastewater.

Enhanced Removal of Bordeaux B and Red G Dyes Used in Alpaca Wool Dying from Water Using Iron-Modified Activated Carbon

The aim of this research was to explore the removal of Red G and Bordeaux B dyes from water using a packed bed column with conventional carbon (C‐conv) and iron‐modified activated carbon (C–FeCl3). The bands increased in C–FeCl3, corresponding to groups already existing in C‐conv, such as C = C and C‐C, and the appearance of new groups, such as C‐O, C‐Cl, Fe‐Cl and Fe‐O. The total ash content (CT) was CT = (10.53 ± 0.12 and 8.98 ± 0.21)% for C‐conv and C–FeCl3, respectively. A molecular structure in the shape of a cross was noticed in Bordeaux B, which was less complex and smaller than the one in Red G. For fixed‐bed columns, the carbon fraction was (0.43 and 0.85) mm. The pH of the adsorbents was 8.55 for C‐conv and 4.14 for C–FeCl3. Breakthrough curves were obtained and the Thomas model (TM) and Yoon–Nelson model (YNM) were applied. The sorption capacity of Bordeaux B on C‐conv and C–FeCl3 was 𝑞TH: (237.88 and 216.21) mg/g, respectively, but the one of Red G was 𝑞TH: (338.46 and 329.42) mg/g. The dye removal (RT) was over 55%. 

Recovery and Concentration of Polyphenols from Roasted Hazelnut Skin Extract Using Macroporous Resins

Hazelnut skin is a rich source of polyphenols but is generally discarded during the roasting process of hazelnuts. Previous studies reported the extraction and identification of these compounds using different solvents and procedures; however, there are few reports on their enrichment and purification. In this study, three types of Amberlite macroporous resins (XAD 16, XAD 4, and XAD 7) were compared to evaluate the enrichment of polyphenols via adsorption and desorption mechanisms. The operating condition parameters for polyphenol adsorption/desorption of each resin were determined, the kinetics of adsorption were examined, and a method for polyphenol recovery was developed using static and dynamic adsorption/desorption. Antioxidant activity and high-performance liquid chromatography-diode array detection were used to confirm the increase in polyphenols obtained using the adsorption/desorption technique. XAD16 showed the highest adsorption capacity, with a recovery of 87.7%, and the adsorption kinetics fit well with a pseudo-second-order model. The highest poly-phenol desorption ratio was observed using an ethanol/water solution (70% v/v) at a flow rate of 1.5 bed volume/h.