Herein, a highly efficient and sustainable adsorbent of cross-linked chitosan-glyoxal/algae biocomposite (CHT-GLX/ALG) adsorbent was developed through an innovative hydrothermal cross-linking method. The CHT-GLX/ALG biocomposite was characterized using several complementary analytical methods that include CHN-O, XRD, FTIR, SEM-EDX, and pHpzc. This new adsorbent, named CHT-GLX/ALG, was utilized for the adsorption of a cationic dye (methyl violet 2B; MV 2B), from synthetic wastewater. The optimization of the dye adsorption process involved key parameters is listed: CHT-GLX/ALG dosage (from 0.02 to 0.1 g/100 mL), pH (from 4 to 10), and contact time (from 20 to 180 min) that was conducted using the Box-Behnken design (BBD). The optimal adsorption conditions for the highest decolorization efficiency of MV 2B (97.02 %) were estimated using the statistical model of the Box-Behnken design. These conditions include a fixed adsorbent dosage of 0.099 g/100 mL, pH 9.9, and a 179.9 min contact time. The empirical data of MV 2B adsorption by CHT-GLX/ALG exhibited favorable agreement with the Freundlich isotherm model. The kinetic adsorption profile of MV 2B by CHT-GLX/ALG revealed a good fit with the pseudo-second-order model. The maximum adsorption capacity (qmax) for MV 2B by CHT-GLX/ALG was estimated at 110.8 mg/g. The adsorption of MV 2B onto the adsorbent can be attributed to several factors, including electrostatic interactions between the negatively charged surface of CHT-GLX/ALG and the MV 2B cation, as well as n-π and H-bonding. These interactions play a crucial role in facilitating the effective adsorption of MV 2B onto the biocomposite adsorbent. Generally, this study highlights the potential of CHT-GLX/ALG as an efficient and sustainable adsorbent for the effective removal of organic dyes.
Due to growing environmental concerns for better waste management, this study proposes developing a composite aerogel using cellulose nanofibers (CNF) and spent coffee grounds (SCG) through an eco-friendly method for efficient methylene blue (MB) adsorption. Adding SCG to the CNF aerogel altered the physical properties: it increases the volume (4.14 cm3 to 5.25 cm3) and density (0.018 to 0.022 g/cm3) but decrease the water adsorption capacity (2064 % to 1635 %). FTIR spectrum showed distinct functional groups in both all aerogels, showing hydroxyl, glyosidic bonds, and aromatic compounds. Additionally, SCG improved thermal stability of the aerogels. In term of adsorption efficacy, CNF-SCG40% aerogel as exceptionally well. According to Langmuir isotherm models, the adsorption of MB happened in a monolayer, with CNF-SCG40% showing a maximum adsorption capacity of 113.64 mg/g, surpassing CNF aerogel (58.82 mg/g). The study identified that the pseudo-second-order model effectively depicted the adsorption process, indicating a chemical-like interaction. This investigation successfully produced a single-use composite aerogel composed of CNF and SCG using an eco-friendly approach, efficiently adsorbing MB. By utilizing cost-effective materials and eco-friendly methods, this approach offers a sustainable solution for waste management, contributes to an eco-friendly industrial environment, and reduces production expenses and management costs.
This study reports the analysis of diclofenac removal from aqueous solution using a novel adsorbent coating with amphoteric surface. This adsorbent coating was improved using a new amphoteric ratio to increase its performance for the removal of pharmaceuticals such as diclofenac. The adsorbent coating was formulated using acrylic polymer emulsion, smectite-based clay powder and epichlorohydrin-dimethylamine to obtain a layer form via the implementation of a facile synthesis method. In a previous study, this adsorbent coating was successful to remove cationic and anionic dyes. Therefore, this research aimed to further investigate and test its application in the removal of other emerging water pollutants like pharmaceuticals. SEM, EDX, and FTIR analyses were carried out for the characterization of this novel adsorbent. The effects of adsorbent composition, diclofenac concentration, temperature, and solution pH were studied and modeled. The best conditions to improve the diclofenac adsorption was 303 K and pH 3 where the adsorption capacity was 25.59 mg/g. Adsorption isotherms and kinetics were quantified and modeled, and the corresponding adsorption mechanism was also analyzed. Diclofenac adsorption with this novel material was exothermic and spontaneous. This alternative adsorbent is promising for diclofenac removal from industrial wastewater systems.
White tea contains the highest flavonoids compared to other teas. While there have been numerous studies on the components of different tea varieties, research explicitly focusing on the flavonoid content of white tea remains scarce, making the need for a good flavonoid purification process for white tea even more important. This study compared the adsorption and desorption performance of five types of macroporous resins: D101, HP20, HPD500, DM301, and AB-8. Among the tested resins, AB-8 was selected based on its best adsorption and desorption performance to investigate the static adsorption kinetics and dynamic adsorption-desorption purification of white tea flavonoids. The optimal purification process was determined: adsorption temperature 25 °C, crude tea flavonoid extract pH 3, ethanol concentration 80 %, sample loading flow rate and eluent flow rate 1.5 BV/min, and eluent dosage 40 BV. The results indicated that the adsorption process followed pseudo-second-order kinetics. Under the above purification conditions, the purity of the total flavonoids in the purified white tea flavonoid increased from approximately 17.69 to 46.23 %, achieving a 2.61-fold improvement, indicating good purification results. The purified white tea flavonoid can be further used for nutraceutical and pharmaceutical applications.
This study highlights the effectiveness of oyster shell biocomposite for the biosorption of Cd(II) and Pb(II) ions from an aqueous solution. The aim of this work was to modify a novel biocomposite derived from oyster shell for the adsorption of Cd(II) and Pb(II) ions from aqueous solution. The studied revealed the specific surface BET surface area was 9.1476 m2/g. The elemental dispersive x-ray analysis (EDS) indicated that C, O, Ag, Ca were the predominant elements on the surface of the biocomposite after which metals ions of Cd and Pb were noticed after adsorption. The Fourier transform Irradiation (FT-IR) revealed the presence of carboxyl and hydroxyl groups on the surface. The effect of process variables on the adsorption capacity of the modified biocomposite was examined using the central composite design (CCD) of the response surface methodology (RSM). The process variables which include pH, adsorbent dose, the initial concentration and temperature were the most effective parameters influencing the uptake capacity. The optimal process conditions of these parameters were found to be pH, 5.57, adsorbent dose, 2.53 g/L, initial concentration, 46.76 mg/L and temperature 28.48°C for the biosorption of Cd(II) and Pb(II) ions from aqueous solution at a desirability coefficient of 1. The analysis of variance (ANOVA) revealed a high coefficient of determination (R2 > 0.91) and low probability coefficients for the responses (P < 0.05) which indicated the validity and aptness of the model for the biosorption of the metal ions. Experimental isotherm data fitted better to the Langmuir model and the kinetic data fitted better to the pseudo-second-order model. Maximun Cd(II) and Pb(II) adsorption capacities of the oyster shell biocomposite were 97.54 and 78.99 mg/g respectively and was obtained at pH 5.56 and 28.48°C. This investigation has provided the possibility of the utilization of alternative biocomposite as a sustainable approach for the biosorption of heavy metal ions from the wastewater stream.
The Yoon-Nelson model serves as a widely used tool for describing the breakthrough behavior of organic micropollutants within fixed bed adsorbers. This study aims to augment its modeling efficacy through two proposed refinements found in the literature: a logarithmic transformation and the incorporation of steric hindrance effects. We systematically evaluated the original Yoon-Nelson model alongside the modified versions, using breakthrough data associated with micropollutant adsorption on solid materials. Three distinct cases were scrutinized: (1) caffeine adsorption on activated carbon; (2) tetracycline adsorption on hierarchical porous carbon; and (3) diclofenac adsorption on organoclay. While all three models demonstrated comparable performance with highly symmetric breakthrough data in case 1, their efficacy diverged significantly when confronted with strongly asymmetric breakthrough data in cases 2 and 3. The original Yoon-Nelson model and the logarithmically modified version fell short in accurately representing these intricate breakthrough curves. In contrast, the version incorporating steric hindrance effects showcased substantial accuracy, outperforming other models in capturing the complexities of asymmetric breakthrough data. This advancement markedly enhances the modeling accuracy and versatility of the Yoon-Nelson model, particularly in assessing the dynamic behavior of organic micropollutants within fixed bed adsorbers.
Heavy metal pollution is one of the most pervasive environmental problems globally. Novel finely tuned algae have been proposed as a means to improve the efficacy and selectivity of heavy metal biosorption. This article reviews current research on selective algal heavy metal adsorption and critically discusses the performance of novel biosorbents. We emphasize emerging state-of-the-art techniques that customize algae for enhanced performance and selectivity, particularly molecular and chemical extraction techniques as well as nanoparticle (NP) synthesis approaches. The mechanisms and processes for developing novel algal biosorbents are also presented. Finally, we discuss the applications, challenges, and future prospects for modified algae in heavy metal biosorption.
To compare the efficacy of Coupled Plasma Filtration and Adsorption (CPFA) plus Continuous Veno-Venous Haemofiltration (CVVH) versus CVVH alone as an adjunct treatment of sepsis in terms of haemodynamic stability, inotropic requirement and inflammatory mediators.
Availability of quality-certified water is pertinent to the production of food and pharmaceutical products. Adverse effects of manganese content of water on the corrosion of vessels and reactors necessitate that process water is scrutinized for allowable concentration levels before being applied in the production processes. In this research, optimization of the adsorption process conditions germane to the removal of manganese from biotreated palm oil mill effluent (BPOME) using zeolite 3A subsequent to a comparative adsorption with clinoptilolite was studied. A face-centered central composite design (FCCCD) of the response surface methodology (RSM) was adopted for the study. Analysis of variance (ANOVA) for response surface quadratic model revealed that the model was significant with dosage and agitation speed connoting the main significant process factors for the optimization. R(2) of 0.9478 yielded by the model was in agreement with predicted R(2). Langmuir and pseudo-second-order suggest the adsorption mechanism involved monolayer adsorption and cation exchanging.
Throughout the application of enhanced oil recovery (EOR), surfactant adsorption is considered the leading constraint on both the successful implementation and economic viability of the process. In this study, a comprehensive investigation on the adsorption behaviour of nonionic and anionic individual surfactants; namely, alkyl polyglucoside (APG) and alkyl ether carboxylate (AEC) was performed using static adsorption experiments, isotherm modelling using (Langmuir, Freundlich, Sips, and Temkin models), adsorption simulation using a state-of-the-art method, binary mixture prediction using the modified extended Langmuir (MEL) model, and artificial neural network (ANN) prediction. Static adsorption experiments revealed higher adsorption capacity of APG as compared to AEC, with sips being the most fitted model with R2 (0.9915 and 0.9926, for APG and AEC respectively). It was indicated that both monolayer and multilayer adsorption took place in a heterogeneous adsorption system with non-uniform surfactant molecules distribution, which was in remarkable agreement with the simulation results. The (APG/AEC) binary mixture prediction depicted contradictory results to the experimental individual behaviour, showing that AEC had more affinity to adsorb in competition with APG for the adsorption sites on the rock surface. The adopted ANN model showed good agreement with the experimental data and the simulated adsorption values for APG and AEC showed a decreasing trend as temperature increases. Simulating the impact of binary surfactant adsorption can provide a tremendous advantage of demonstrating the binary system behaviour with less experimental data. The utilization of ANN for such prediction procedure can minimize the experimental time, operating cost and give feasible predictions compared to other computational methods. The integrated workflow followed in this study is quite innovative as it has not been employed before for surfactant adsorption studies.
Biochar modified with calcium source is acted as an effective adsorbent for phosphorous recovery. In this research, eggshell is used as a low-cost and environmentally friendly calcium source to replace chemical reagents such as CaCO3, Ca(OH)2 and CaCl2 used in the modified biochar production. Biochar derived from rape straw and modified with eggshell shows prominent phosphorous adsorption performance (e.g., equilibrium adsorption amount, 109.7 mg/g). The kinetic and isotherm analysis demonstrate that chemical adsorption process is performed as the main controlled step for the modified biochar adsorption, and the phosphate adsorption process is composed of both monolayer adsorption and multi-layer adsorption. Moreover, it is found from the physicochemical structures comparison before and after phosphate adsorption that Ca-P precipitation, hydrogen bonding and electrostatic attraction are identified as main adsorption mechanisms. In addition, the adsorbed phosphates are mainly distributed inside the space with pore sizes of 15-50 nm.
The emission of waste anaesthetic gas is a growing contributor to global warming and remains a factor in atmospheric ozone depletion. Volatile anaesthetics in medical waste gases could be removed via adsorption using suitable activated carbon materials possessing an enhanced affinity to anaesthetic molecules. In this work, the effects of surface physical and chemical properties on sevoflurane adsorption were investigated by oxidative hydrothermal surface modification of a commercial activated carbon using only distilled water. The hydrothermal surface modification was carried out at different treatment temperatures (150-300 °C) for varying durations (10-30 min), and adsorption was conducted under fixed conditions (bed depth = 10 cm, inlet concentration = 528 mg/L, and flow rate = 3 L/min). The hydrothermal treatment generally increased the BET surface area of the activated carbons. At oxidation temperatures above 200 °C, the micropore volume of the samples diminished. The relative amount of surface oxygen was enriched as the treatment temperature increased. Treatment duration did not significantly affect the introduction of relative amount of surface oxygen, except at higher temperatures. There were no new types of functional groups introduced. However, disappearance and re-formation of oxygen functional groups containing C-O structures (as in hydroxyl and ether groups) occurred when treatment temperature was increased from 150 to 200 °C, and when treatments were conducted above 200 °C, respectively. The ester/acetal groups were enriched under the temperature range studied. The findings suggested that the re-formation of surface oxygen functionalities might lead to the development of functional groups that improve sevoflurane adsorption.
Chitosan-ethylene glycol diglycidyl ether/TiO2 nanoparticles (CS-EGDE/TNP) composite was synthesized to be biosorbent for the removal of reactive orange 16 (RO16) dye from aqueous solution. The CS-EGDE/TNP composite was characterized via BET, XRD, FTIR, and SEM-EDX techniques. Response surface methodology (RSM) with Box-Behnken design (BBD) was applied to optimize the adsorption key parameters such as adsorbent dose (A: 0.02-0.08 g/L), RO16 dye concentration (B: 20-80 mg/L), solution pH (C: 4-10), temperature (D: 30-50 °C), and contact time (E: 30-90 min). The adsorption isotherm followed Freundlich model and pseudo-second order (PSO) kinetic model. The adsorption capacity of CS-EGDE/TNP for RO16 dye was 1407.4 mg/g at 40 °C. The adsorption mechanism of RO16 dye on the surface of CS-EGDE/TNP can be attributed to various interactions such as electrostatic attraction, n-π interaction, Yoshida H-bonding, and H-bonding. Results supported the potential use of CS-EGDE/TNP as effective adsorbent for the treatment of acid reactive dye.
The removal of methyl orange (MO) dye has been studied using TiO2/chitosan-montmorillonite (TiO2/Cs-MT) bilayer photocatalyst which also functions as an adsorbent. The dye removal experiments were conducted in the dark and under UV-Vis light irradiation via adsorption and photocatalysis-adsorption processes, respectively. The adsorption modelings were employed on the dark experimental data and compared with the immobilized and suspended Cs-Mt counterparts. It was found that the bilayer photocatalyst closely followed the adsorption properties of immobilized Cs-Mt which obeyed the pseudo-second-order kinetic and film diffusion models. Fluorescent analysis revealed that the charge separation was enhanced in the presence of Cs-Mt as a sub-layer of TiO2. Under light irradiation, the photocatalytic activity of TiO2/Cs-MT corresponded to its adsorption counterpart trend and was optimized at pH 6.5 and 20 mg L-1 of MO dye solution. High removal efficiency and synergism of MO by TiO2/Cs-MT over TiO2 single layer were observed throughout the 10 cycles of application due to contribution of adsorption of Cs-Mt sub-layer and photocatalysis by TiO2 top layer.
This study reports the application of hydrated lime for the effective adsorption of the heavy mercury metal from the aqueous phase solutions. Initially, hydrated lime was subjected to structural characterization and thermal stability analysis. The FT-IR spectrum analysis revealed that the existence of the O-H bonds as a confirmation of hydrated lime formation. Subsequently, the XRD powder-based analysis demonstrated that most of the hydrated lime is pure crystalline material known as Portlandite while a small amount of calcite is also present in the structure of the hydrated lime. The thermal stability analysis revealed that the hydrated lime is highly thermally stable under harsh conditions without decomposing at higher temperatures up to 500 °C. Furthermore, the hydrated lime was subjected to the selective adsorption of heavy metal mercury to investigate the potential influence of the adsorbent particle size and loading on adsorption capacity. The results demonstrated that the decrease in the adsorbent particle size leads to the improvement in the mercury adsorption attributing to the rise in specific surface area. The enhancement in the loading of the adsorbent resulted in a reduction in mercury adsorption directing to the fact that already adsorbed metal ions onto the adsorbent surface lead to hindrance for the adsorption of other ions of heavy metal. These results lead to a significant impact on modern in inventing different adsorbents with promising water treatment efficiency for more industrial applications and the related recovery of mercury.
Increased disposal of heavy metals, including lead (II) (Pb(II)) into the environment calls for a reliable and sustainable solution. In this study, nano-sized biochar from sago activated sludge was proposed for the removal of Pb(II). Sago activated sludge was pyrolysed in a tube furnace followed by a chemical activation to yield nano-sized particles ranging from 45 to 75 nm. The nano-sized biochar obtained was characterised and the influence of pH (2 – 10), initial Pb(II) concentration (1 – 5 mg/L), contact time (30 – 90 mins) and adsorbent dosage (0.1 – 0.5 g) was investigated in a batch adsorption study. Response surface methodology (RSM) approach with central composite design (CCD) was used as statistical tools to optimize the adsorption process by relating the mutual interactions among all studied variables. Characterisation of the prepared adsorbent showed that large surface area was observed on sludge activated carbon (78.863 m2 /g) compared with sludge biochar (8.044 m2 /g) and sludge biomass (1.303 m2 /g). The batch adsorption best fitted the Langmuir isotherm (maximum adsorption capacity, Q0 = 3.202 × 10-3 mg/g, R-squared value = 0.9308). The RSM indicated that the optimum Pb(II) removal (99.87%) was at 0.5 g of adsorbent, 5 mg/L initial concentration and 30 min contact time. This study is significant because utilisation of sago effluent will reduce sago manufacturing waste by conversion into a value-added product as adsorbent to adsorb Pb(II) in wastewater.
In order to meet the growing demand for adsorbents to treat wastewater effectively, there has been increased interest in using sustainable biomass feedstocks. In this present study, the dermal tissue of oil palm frond was pyrolyzed with superheated steam at 500 °C to produce nanoporous biochar as bioadsorbent. The effect of operating conditions was investigated to understand the adsorption mechanism and to enhance the adsorption of phenol and tannic acid. The biochar had a microporous structure with a Brunauer-Emmett-Teller surface area of 422 m2/g containing low polar groups. The adsorption capacity of 62.89 mg/g for phenol and 67.41 mg/g for tannic acid were obtained using 3 g/L biochar dosage after 8 h of treatment at solution pH of 6.5 and temperature of 45 °C. The Freundlich model had the best fit to the isotherm data of phenol (R2 of 0.9863), while the Langmuir model best elucidated the isotherm data of tannic acid (R2 of 0.9632). These indicated that the biochar-phenol interface was associated with a heterogeneous multilayer sorption mechanism, while the biochar-tannic acid interface had a nonspecific monolayer sorption mechanism. The residual concentration of 26.3 mg/L phenol and 23.1 mg/L tannic acid was achieved when treated from 260 mg/L three times consecutively with 1 g/L biochar dosage, compared to a reduction to 72.3 mg/L phenol and 69.9 mg/L tannic acid using 3 g/L biochar dosage in a single treatment. The biochar exhibited effective adsorption of phenol and tannic acid, making it possible to treat effluents that contain varieties of phenolic compounds.
The combination of exceptional functionalities offered by 3D graphene-based macrostructures (GBMs) has attracted tremendous interest. 2D graphene nanosheets have a high chemical stability, high surface area and customizable porosity, which was extensively researched for a variety of applications including CO2 adsorption, water treatment, batteries, sensors, catalysis, etc. Recently, 3D GBMs have been successfully achieved through few approaches, including direct and non-direct self-assembly methods. In this review, the possible routes used to prepare both 2D graphene and interconnected 3D GBMs are described and analyzed regarding the involved chemistry of each 2D/3D graphene system. Improvement of the accessible surface of 3D GBMs where the interface exchanges are occurring is of great importance. A better control of the chemical mechanisms involved in the self-assembly mechanism itself at the nanometer scale is certainly the key for a future research breakthrough regarding 3D GBMs.
In this study, a response surface methodology (RSM) approach using central composite design (CCD) was investigated to develop a mathematical model and to optimize the effects of pH, adsorbent amount and temperature related to the hexavalent chromium removal by biosorption on peanut shells (PSh). The highest removal percentage of 30.28% was found by the predicted model under the optimum conditions (pH of 2.11, 0.73 g of PSh and 37.2 °C) for a 100 mg/L initial Cr(VI) concentration, which was very near to the experimental value (29.92%). The PSh was characterized by SEM, EDX, FTIR, BET, XRD analyses. Moreover, a Langmuir isotherm fitted well (R2 = 0.992) with the experimental data, and the maximum adsorption capacity was discovered to be 2.48 and 3.49 mg/g respectively at 25 and 45 °C. Kinetic data were well foreseen by pseudo second order. Thermodynamic study depicted that biosorption of Cr(VI) onto PSh was spontaneous and endothermic. Regeneration of the PSh using NaOH showed a loss <5% in the Cr(VI) removal efficiency up to three recycle runs. In summary, the Cr(VI) removal onto economic, sensitive and selective biosorbent (PSh) was optimized using CCD to study biosorption behaviors.
Copper (Cu) ion in wastewater is considered as one of the crucial hazardous elements to be quantified. This research is established to predict copper ions adsorption (Ad) by Attapulgite clay from aqueous solutions using computer-aided models. Three artificial intelligent (AI) models are developed for this purpose including Grid optimization-based random forest (Grid-RF), artificial neural network (ANN) and support vector machine (SVM). Principal component analysis (PCA) is used to select model inputs from different variables including the initial concentration of Cu (IC), the dosage of Attapulgite clay (Dose), contact time (CT), pH, and addition of NaNO3 (SN). The ANN model is found to predict Ad with minimum root mean square error (RMSE = 0.9283) and maximum coefficient of determination (R2 = 0.9974) when all the variables (i.e., IC, Dose, CT, pH, SN) were considered as input. The prediction accuracy of Grid-RF model is found similar to ANN model when a few numbers of predictors are used. According to prediction accuracy, the models can be arranged as ANN-M5> Grid-RF-M5> Grid-RF-M4> ANN-M4> SVM-M4> SVM-M5. Overall, the applied statistical analysis of the results indicates that ANN and Grid-RF models can be employed as a computer-aided model for monitoring and simulating the adsorption from aqueous solutions by Attapulgite clay.