Characterization of Residual Biomasses and Its Application for the Removal of Lead Ions from Aqueous Solution

Use of different food wastes as green biosorbent: isotherm, kinetic, and thermodynamic studies of Pb2

Lead (Pb2+) can contaminate waters from many sources, especially industrial activities. This heavy metal is an amphoteric, toxic, endocrine-disrupting, bioaccumulative, and carcinogenic pollutant. One of the effective and economical processes used to remove lead from water is adsorption. The fact that the adsorbents used in this method are easily available and will contribute to waste minimization is the primary reason for preference. In this study, the adsorption abilities and surface properties of tea waste (TW), banana peels (BP), almond shells (AS), and eggshells (ES) which are easily available do not need modification and have very high (> 90%) removal efficiencies presented with isotherm, kinetic, and thermodynamic perspectives as detail. The surface structures and elemental distribution of raw adsorbents were revealed with SEM/EDX. Using FTIR analysis, carboxylic (-COOH) and hydroxyl groups (-OH) in the structure of TW, AS, BP, and ES were determined. It was determined that the Pb2+ adsorption kinetics conformed to the pseudo-quadratic model and its isotherm conformed to the Langmuir. The optimum adsorption of Pb2+ was ranked as BP > ES > AS > TW with 100, 68.6, 51.7, and 47.8 mg/g qm, respectively. The fact that the process has negative ΔG° and positive ΔH° values from a thermodynamic point of view indicates that it occurs spontaneously and endothermically. According to the experimental data, the possible adsorption mechanism for Pb2+ has occurred in the form of physisorption (van der Waals, electrostatic attraction) and cooperative adsorption including chemisorption (complexation, ion exchange) processes.

Water Cleaning by a Continuous Fixed-Bed Column for Cr(VI) Eco-Adsorption with Green Adsorbent-Based Biomass: An Experimental Modeling Study

In this study, chromate adsorption onto red peanut skin (RPS) was investigated in a fixed-bed column; FTIR, PZC, SEM, DLS, and BET were used to evaluate its adsorption properties. The experiments were conducted to determine the effect of physical parameters, including the inlet initial Cr(VI) concentration (100–500 mg L−1), bed height (10–20 cm), and feed flow rate (13.59–23.45 mL min−1). They were carried out to predict breakthrough curves. The adsorption capacity coefficients were determined using the most widely used Bohart–Adams model. It was tested to fit experimental data, for a better understand the dynamic behavior, and for further optimize column performance. It was found that the Cr(VI) uptake decreases when increasing the flow rate and that high chromate concentration and bed height consequently increase the column’s life span. A high column adsorption capacity can be achieved with a higher Cr(VI) concentration due to the higher driving force. The results indicated that the Bohart–Adams model provides a good description (R2 > 0.98) of the experimental data of the Cr(VI)’s removal from the aqueous solution on the RPS suggesting that the surface diffusion is the rate-limiting step in the continues adsorption process.. Breakthrough adsorption capacity is crucial for comparing RPS with other similar materials. Indeed, possible mechanisms have been suggested for illustrating adsorption onto RPS. The obtained results showed significant potential of 26.23 mg g−1 of RPS on Cr(VI) elimination at a natural pH of 5.35. Furthermore, this global investigation allowed for the design of a promising low-cost material for the future scale-up of cleaning wastewater polluted by metal and determine the properly conditions for operating column adsorption. This material provides an economical, efficient means of eliminating pollutants, thus meeting the main aims of the UN Sustainable Development Goals (UN SDGs).

Dynamic Removal of Nickel (II) on Elaeis guineensis Waste Bed: Study of the Breakage Curve and Simulation

This research focused on the use of residual fiber from oil palm (Elaeis guineensis) for Ni (II) adsorption in a packed bed column. An analysis was conducted on the effect and statistical incidence of changes in temperature, adsorbent particle size, and bed height on the adsorption process. The results showed that particle size and bed height significantly affect the adsorption of Ni (II) ions, reaching adsorption efficiencies between 87.24 and 99.86%. A maximum adsorption capacity of 13.48 mg/g was obtained in the bed with a break time of 180 min. The Ni (II) adsorption in the dynamic system was evaluated by the analysis of the breakage curve with different theoretical models: Yoon-Nelson, dose-response, and Adams-Bohart; the dose-response model was the most appropriate to describe the behavior of the packed bed with an R² of 84.56%. The breakthrough curve obtained from Aspen Adsorption^® appropriately describes the experimental data with an R² of 0.999. These results indicate that the evaluated bioadsorbent can be recommended for the elimination of Ni (II) in aqueous solutions in a dynamic system, and the simulation of the process can be a tool for the scalability of the process.

Metanil Yellow dye adsorption using green and chemical mediated synthesized manganese ferrite: An insight into equilibrium, kinetics and thermodynamics

Green Manganese Ferrite (GMF) and Chemical mediated Manganese Ferrite (CMF) were designed and prepared via in situ co-precipitation method and their adsorption potential was compared using the model dye, Metanil Yellow (MY). Previously, an extract of aquatic macrophyte and metal chloride were employed for the development of ecofriendly GMF. Alternatively, CMF has been synthesized through chemical co-precipitation from metal chloride precursors. Several characterization methods, including PSA, BET, TGA, DSC, FTIR, SEM, VSM, EDX, and XRD, were analyzed to reveal the structural and functional properties of the as-synthesized GMF and CMF. Their MY adsorption performances were tested as the function of the operational conditions such as initial solution pH, temperature, nanocomposite dosage, and dye concentration in a batch mode of operation. The pseudo-second order MY adsorption process fits best in Langmuir model which yielded the maximal monolayer adsorption capacity (q_max) of 391.34 mg/g for GMF and 271.89 mg/g for CMF. This outperformance of GMF over CMF was observed due to the augmentation of specified surface functional moieties derived from the phyto-constituents of macrophages. Further, the thermodynamic studies confirmed the chemisorptive and exothermic nature of adsorption processes. Conclusively, with the ease of regeneration and reuse potential, GMF and CMF could be viable contenders for scale up and industrial applications.

Elimination of Chromium (VI) and Nickel (II) Ions in a Packed Column Using Oil Palm Bagasse and Yam Peels

The single-component adsorption of chromium (VI) and nickel (II) on oil palm bagasse (OPB) and yam peels (YP) in a packed bed column was explored and improved using a central 22-star T composite design. The temperature, bed height, and particle size were evaluated, and the optimized response variable was the removal efficiency. The remaining concentration of heavy metals in solution was determined by Ultraviolet–Visible and Atomic Absorption Spectroscopy. It was found that bioadsorbents have a porous structure, with the presence of functional groups such as hydroxyl, carboxyl, and amino, which favor adsorption processes, and that the adsorption mechanisms controlling the process is cation exchange, precipitation, and complexation on the exposed surface of the biomaterials. In the adsorption trials, removal percentages higher than 87% were obtained in all cases, showing better results in the removal of Cr(VI), and that particle size is the most influential factor. Maximum Cr(VI) capacities of 111.45 mg g−1 and 50.12 mg g−1 were achieved on OPB and YP, respectively, while for nickel values of 103.49 mg g−1 and 30.04 mg g−1 were obtained. From the adjustment of the breakthrough curve to the models, it was determined that the model best able to adjust the data was the Thomas model, and the thermodynamic parameters of Cr(VI) and Ni(II) removal suggest that the process on YP is endothermic, while on OPB it is exothermic. In both biomaterials, the process is controlled by spontaneous chemisorption with a great affinity of the active centers for the ions.

Adsorptive Capacity of Calcinated Hen Eggshell Blended with Silica Gel for Removal of Lead II Ions from Aqueous Media: Kinetics and Equilibrium Studies

In this study, a description was given for the adsorbent CaSiO₃ for allure proximate examination and determination like particle density, main part density, and porosity analysis. This is performed before management of batch adsorption experiments. Both kinetics and balance studies for the adsorbent were examined. The influences of various process parameters like lead concentration, pH, adsorbent dosage, and contact temporal length for process removal were explored. The removal efficiency of CaO from eggshell was enhanced to increase after mixing it with silica coagulate compared with added scholar's findings for the same limit. The maximum removal efficiency (99.58%) was obtained by limiting the pH, adsorbent dosage, initial lead concentration, and contact time at 4, 1.8 g, 35 g/L, and 140 minutes, respectively. Thus, blending CaO from eggshells with silica gel can increase the adsorption competency of CaO. Lead removal is well integrated into the Langmuir isotherm model with an equivalent factor of 0.991. The kinetic data of adsorption fit well into a pseudo-first-order model with a correlation coefficient of 0.90111. The pseudo-second-order model was the rate-determining step involved in the lead adsorption process for calcium silicate (CaSiO₃) adsorbents.

Stability of biochar derived from banana peel through pyrolysis as alternative source of nutrient in soil: feedforward neural network modelling study

Biochar derived from banana peels can be used as an alternative nutrient in the soil that can promote crop growth while reducing fertiliser usage. Biochar stability has proportional relationship to biochar residence time in the soil and potassium is one of the vital nutrients needed for plant growth. This research aims at providing optimum pyrolysis operating conditions like temperature, residence time, and heating rate using banana peels as feedstock. An electrical tubular furnace was used to conduct the pyrolysis process to convert banana peels into biochar. The elemental compositions of biochar are potassium, oxygen (O), and carbon (C) content. The O:C ratio was used as the biochar stability indicator. Analysis of results showed that operating temperature has the most remarkable effect on biochar yield, biochar stability, and biochar's potassium content. In addition, a multilayer feedforward artificial neural network model was developed for the pyrolysis process. Eleven training algorithms were selected to model the multi-input multi-output neural network (MIMO). The most suitable training algorithm was identified through four performance criterions which are root mean square error (RMSE), mean absolute error (MSE), mean absolute percentage error (MAPE), and regression (R²). The results show that the Levenberg-Marquardt backpropagation training algorithm has the lowest error. From the chosen training algorithm, neural network was trained, and optimum operating parameters for banana peel were predicted at 490 °C, 110 min, and 11 °C/min with a high yield of 47.78%, O/C ratio of 0.2393, and 14.04 wt. % of potassium.

Potential Use of Residual Sawdust of Eucalyptus globulus Labill in Pb (II) Adsorption: Modelling of the Kinetics and Equilibrium

The raw sawdust of Eucalyptusglobulus Labill was studied as an alternative of residual biomaterial for the adsorption of lead (II) in wastewater, evaluating the effect of pH (3, 4, 5, and 6) in a batch system. From the characterization of the biomaterial, it was found that the biomass has a low ash content, and from the scanning electron microscopy (SEM) microphotographs that it presents a porous morphology with diverse texture and presence of fiber fragments, which describe the heterogeneity of the material. The Fourier transform infrared (FTIR) spectrum showed the presence of functional groups of NHR, OH, COOH, and hydrocarbons, which are part of the structure of lignin, cellulose, hemicellulose, and pectin. From the adsorption experiments, it was obtained that the optimal value of pH 6, reaching a removal percentage of 96% and an adsorption capacity of 4.80 mg/g. The model that better adjusted the kinetics results was the pseudo-second-order model and the Langmuir and Freundlich isothermal models described the adsorption equilibrium; it was found that in the system prevails chemisorption, supported in ion exchange by Pb (II) and the biomass’ functional groups. From the results, eucalyptus sawdust is suggested as a low-cost adsorbent for Pb (II) bioadsorption present in solution.

Efficient photocatalytic degradation of dyes using photo-deposited Ag nanoparticles on ZnO structures: simple morphological control of ZnO

In this work, morphology-controlled ZnO structures were prepared via a hydrothermal method by simple adjustments in the NaOH concentration. The NaOH concentration variation from 0.2 to 1.2 M resulted in the formation of ZnO structures in shapes such as walnut, spherical flower, flower, rod, and urchin-like. The extent of OH- ions is the main factor influencing the growth of ZnO structures. Well-defined morphologies, good crystallinity, and optical properties were obtained for all ZnO structures. Among these ZnO structures, ZnOsf (spherical flower-like) structure showed a greater percentage of photodegradation of methyl orange and rhodamine B dyes. Surface plasmon resonance was achieved by modifying the surface of ZnO with Ag nanoparticles. ZnOsf was loaded with Ag nanoparticles by a facile photo-deposition method. Ag-ZnOsf showed superior photoactivity and recyclability for the degradation of methyl orange and rhodamine B. Therefore, modification of different ZnO structures can help realize potential catalysts for future environmental applications.

Efficient removal of Cr (VI) and Co (II) from aqueous solution by activated carbon from Manihot esculenta Crantz agricultural bio-waste

Heavy metals are one of the most dangerous and critical threats to human and environment. In this study, the adsorption efficiency of activated carbon from cassava peels considered as agricultural waste (CPR) was evaluated for removal of heavy metals Cr (VI) and Co (II) from aqueous media. Cassava peel carbon (CPC) was obtained by acid treatment. Structural and morphological properties were investigated using Fourier Transform Infra-Red (FTIR), Scanning Electron Microscopy (SEM), Brunauer-Emmet-Teller surface area (BET) and X-Ray Diffraction (XRD). The adsorption experiments were conducted in batch mode under natural solution pH and complexation of the heavy metals, which allows the use of UV-Visible spectroscopy technique. CPC adsorbent exhibited a high adsorption capacity, according to Langmuir model, for Cr (VI) (166.35 mg/g) and Co (II) (301.63 mg/g) at 25 °C. Kinetic and adsorption isotherms followed the pseudo second-order and Langmuir isotherm models for both metals, respectively. Thermodynamic study confirmed the spontaneity and endothermic nature of both metals adsorption onto CPC surface.