Comparative research on selective adsorption of Pb(II) by biosorbents prepared by two kinds of modifying waste biomass: Highly-efficient performance, application and mechanism

Simultaneous removal of heavy metals and antibiotics from anaerobically digested swine wastewater via functionalized covalent organic frameworks

The removal of heavy metal ions and antibiotics from livestock and poultry wastewater has gained significant attention. Developing dual-functional materials capable of simultaneously removing heavy metal ions and antibiotics from wastewater is a promising strategy. In this study, a functionalization approach was proposed to enhance active sites in covalent organic frameworks (COFs), thereby improving their adsorption performance and maintaining photocatalytic activity. Vinyl-functionalized covalent organic frameworks (COFs-V) were first synthesized in a room-temperature solution. Subsequently, 4-mercaptobenzoic acid was introduced into COFs-V via grafting and chelation to prepare COF@COOH, aiming to modify surface active sites. Fourier transform infrared spectroscopy (FTIR) and in-situ X-ray photoelectron spectroscopy (XPS) confirmed the successful introduction of carboxyl groups into COF@COOH, significantly increasing the number of active sites. The performance and mechanism of COF@COOH in the removal of Cu2+, Zn2+, and tetracycline hydrochloride (TC) from swine wastewater were systematically studied. The results revealed that the adsorption capacities of COF@COOH for Cu2+ and Zn2+ reached 19.27 mg/g and 12.95 mg/g, respectively, which were 58 and 29 times higher than those of the unmodified COFs. Additionally, COF@COOH completely degraded TC within 5 min, with 100% photocatalytic degradation efficiency and an apparent rate constant of 1.13 min-1. After five cycles, the adsorption capacities for Cu2+ and Zn2+ and the degradation efficiency of TC remained nearly unchanged, demonstrating the stability of the composite material. This study provides an effective approach for the simultaneous removal of heavy metal ions and antibiotics from swine wastewater.

Activated Nanocellulose from Corn Husk: Application to As and Pb Adsorption Kinetics in Batch Wastewater

The aim of this study was to evaluate the removal of Pb and As from an aqueous solution using corn residue cellulose nanocrystals (NCCs). The corn husk was subjected to alkaline digestion, followed by bleaching and esterification with 3% citric acid to obtain NCCs. A 10 ppm multimetal solution of Pb and As was prepared. The adsorption process was evaluated by adjusting the pH and NCC dosage, optimized through the nonlinear regression of empirical mathematical models. Based on the optimal parameters, the kinetics were evaluated using the PFO and PSO models. The NCCs displayed nanometer-level characteristics with a particle size less than 383.7 nm, a ζ potential in the range of -28-70 mV, pHZCP with an acidic tendency, a porous crystal structure as evaluated through SEM images, and the presence of functional groups with a high chelating capacity, as identified via FTIR. Optimum values of pH 8.0 and 20 mg/L of the NCC dose were found, from which it was observed that the PFO, PSO, and Elovich kinetics showed R2 > 0.974, with an adsorption capacity in the order Pb > As. The adsorbent-formulated NCCs presented a good capacity to remove heavy metals from aqueous media.

Investigation of the Potential of Repurposing Medium-Density Fiberboard Waste as an Adsorbent for Heavy Metal Ion Removal

Medium-density fiberboard (MDF) waste generation has increased steadily over the past decades, and therefore, the investigation of novel methods to recycle this waste is very important. The potential of repurposing MDF waste as an adsorbent for the treatment of Cd(II), Cu(II), Pb(II), and Zn(II) ions in water was investigated using MDF offcuts. The highest adsorption potential in single-metal ion solution systems was observed for Pb(II) ions. The experimental data of Pb(II) ions fit well with the Freundlich isotherm and pseudo-second-order kinetic models. Complexation and electrostatic interactions were identified as the adsorption mechanisms. The adsorption behavior of multi-metal ion adsorption systems was investigated by introducing Cd(II) ions as a competitive metal ion. The presence of the Cd(II) ions reduced the adsorption potential of Pb(II) ions, yet the preference for the Pb(II) ions remained. Regeneration studies were performed by using 0.1 M HCl as a regeneration agent for both systems. Even though a significant amount of adsorbed metal ions were recovered, the adsorption potential of the MDF was reduced in the subsequent adsorption cycles. Based on these results, MDF fines have the potential to be used as an economical adsorbent for remediation of wastewater containing heavy metal ions.

Biosorption process using Cereus jamacaru DC, Cactaceae for Pb2+ removal from aqueous systems

Lead is a highly toxic metal associated with many human health diseases that can be caused by several environmental changes. Innovative sustainable solutions for water remediation have been recently encouraged by using renewable, low-cost and earth-abundant biomass materials to ensure public health conditions. In this article, Cereus jamacaru DC (popularly known as Mandacaru) was investigated as a biosorbent in the Pb2+ removal from aqueous solution using a two-level factorial design. The analysis of variance suggested a significant and predictive model (R2 = 0.9037). The maximum efficacy of Pb2+ removal in the experimental design was 97.26%, being the optimized conditions: pH 5.0, contact time 4 h without adding NaCl. The Mandacaru was divided into three types according to the plant structure and this parameter did not present a significant interference in the biosorption process. This result corroborates with slight differences in the total soluble proteins, carbohydrates and phenolic compounds found in the Mandacaru types investigated. FT-IR analysis revealed the presence of O-H, C-O and C = O groups that were responsible for the ion biosorption process. The optimized procedure was capable to remove 97.28% of the Pb2+ added in the Taborda river water sample. The kinetic adsorption results show the pseudo-second-order model, suggesting chemisorption process. Thus the treated water sample can be considered in accordance with technical standards issued by CONAMA Resolution Num. 430/2011 and Ordinance GM/MS Num.888/2021 of WHO. In this way, the Mandacaru proved to be an efficient, fast and easy-to-apply bioadsorbent in Pb2+ removal and has great environmental application potential.

Potentials of mono- and multi-metal ion removal from water with cotton stalks and date palm stone residuals

In this work, cotton stalks (Gossypium barbadense) and date palm stones (Phoenix dactylifera) have been used as biosorbents to remove cadmium; Cd(II), lead; Pb(II), and zinc; Zn(II) from mono- and multi-solutions. Each biosorbent was characterized using SEM-EDX, and FT-IR. The findings showed that pH, dose, contact time, metal concentration, and particle size affect the treatment process. The adsorption pattern was Pb(II) > Cd(II) > Zn(II) for both biosorbents. The adsorption performance of cotton stalks was higher than that of date palm stones. The fitted maximum uptake capacities; qm of cotton stalks were higher than those of date palm stones. The maximum adsorption at optimum conditions of Pb(II), Cd(II), and Zn(II) with cotton stalks were 98%, 92.1%, and 78.9%, respectively, within 30 min. While the maximum adsorption of Pb(II), Cd(II), and Zn(II) with date palm stones were 94.6%, 76%, and 68.6%, respectively. Results confirmed the antagonistic effect of heavy metal removal at optimum conditions. Biosorbents could remove ~ 100% of the metal ions from real wastewater samples. Regeneration investigation revealed a successful reusability of both biosorbents for four cycles.

The Adsorption of Pb(II) from Aqueous Solution Using KOH-Modified Banana Peel Hydrothermal Carbon: Adsorption Properties and Mechanistic Studies

Adopting banana peel as a raw material, the adsorption properties of banana peel hydrothermal carbon modified with a KOH solution for lead ions in aqueous solution were studied. The surface structure and functional groups of the modified hydrothermal carbon were analyzed by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, the Brunner-Emmet-Teller (BET) method, element analysis, and Raman spectroscopy. The results showed that an adsorption capacity of 42.92 mg/g and a removal rate of 86.84% were achieved when the banana peel hydrothermal carbon was modified with a KOH solution of 0.5 mol/L, with a pH of 6 and a solid-liquid ratio of 1 g/L. The equilibrium adsorption time for lead ions in solution being adsorbed using KOH-modified hydrothermal carbon was 240 min, the adsorption process satisfied the quasi-second-order kinetic model and the Redlich-Peterson isotherm equation, and the equilibrium removal efficiency was 88.62%. The adsorption of lead ions using KOH-modified hydrothermal carbon is mainly chemical-physical adsorption.

Remediation of water tainted with noxious aspirin and fluoride ion using UiO-66-NH2 loaded peanut shell

One green adsorbent, UiO-66-NH2 modified peanut shell (c-PS-MOF), was prepared in a green synthetic route for improving the capture level of aspirin (ASP) and fluoride ion (F-). The adsorption properties of c-PS-MOF were evaluated by batch experiments and its physicochemical properties were explored by various characterization methods. The results showed that c-PS-MOF exhibited a wide range of pH applications (ASP: 2-10; F-: 3-12) and high salt resistance in the capturing processes of ASP and F-. The unit adsorption capacity of c-PS-MOF was as high as 84.7 mg·g-1 for ASP as pH = 3 and 11.2 mg·g-1 for F- under pH = 6 at 303 K from Langmuir model, respectively. When the solid-liquid ratio was 2 g·L-1, the content of ASP (C0 = 100 mg·L-1) and F- (C0 = 20 mg·L-1) in solution can be reduced to 0.48 mg·L-1 and 1.05 mg·L-1 separately. The recycling of c-PS-MOF can be realized with 5 mmol·L-1 NaOH as eluent. Analysis of simulated water samples showed that c-PS-MOF could be used to remove ASP and F- from actual water. The c-PS-MOF is promising to bind ASP and F- from rivers, lakes, etc.

Soursop (Annona muricata) Properties and Perspectives for Integral Valorization

The increased international interest in the properties of soursop (Annona muricata) alerts us to the sustainability of productive chain by-products, which are rich in phytochemicals and other properties justifying their industrial application in addition to reducing the environmental impact and generating income. Chemical characteristics of soursop by-products are widely known in the scientific community; this fruit has several therapeutic effects, especially its leaves, enabling it to be used by the pharmaceutical industry. Damaged and non-standard fruits (due to falling and crushing) (30-50%), seeds (3-8.5%), peels (7-20%), and leaves, although they constitute discarded waste, can be considered as by-products. There are other less cited parts of the plant that also have phytochemical components, such as the columella and the epidermis of the stem and root. Tropical countries are examples of producers where soursop is marketed as fresh fruit or frozen pulp, and the valorization of all parts of the fruit could represent important environmental and economic perspectives. Based on the chemical composition of the fruit as well as its by-products and leaves, this work discusses proposals for the valorization of these materials. Soursop powder, bioactive compounds, oil, biochar, biodiesel, bio-oil, and other products based on published studies are presented in this work, offering new ideas for opportunities for the regions and consumers that produce soursop.

Modification of sugarcane bagasse with iron(III) oxide-hydroxide to improve its adsorption property for removing lead(II) ions

Lead contamination in wastewater results in toxicity of aquatic life and water quality, it is recommended to remove lead before discharging. Four sugarcane bagasse adsorbent materials of sugarcane bagasse powder (SB), sugarcane bagasse powder doped iron(III) oxide-hydroxide (SBF), sugarcane bagasse powder beads (SBB), and sugarcane bagasse powder doped iron(III) oxide-hydroxide beads (SBFB) were synthesized and characterized with various techniques. Their lead removal efficiencies were investigated by batch experiments on the effects of dose (0.1-0.6 g), contact time (1-6 h), pH (1, 3, 5, 7, 9, 11), and concentration (5-30 mg/L), adsorption isotherms, kinetics, and desorption experiments. All materials were amorphous phases presenting specific peaks of cellulose. SBB and SBFB detected sodium alginate peaks, and iron(III) oxide-hydroxide peaks were detected in SBF and SBFB. SB and SBF were scales or overlapping plate surfaces whereas SBB and SBFB had spherical shapes with coarse surfaces. The main functional groups of O-H, C=O, C-H, C-O, and C=C were observed in all materials, whereas Fe-O and -COOH were only found in materials with adding iron(III) oxide-hydroxide or bead material. The point of zero charges (pH_pzc) of all materials was higher than 4. The optimum conditions of SB, SBF, SBB, and SBFB with the highest lead removal efficiency at a lead concentration of 10 mg/L and pH 5 were 0.6 g and 6 h (96.08%), 0.2 g and 3 h (100%), 0.2 g and 2 h (98.22%), and 0. 1 g and 2 h (100%), respectively. Since SBFB spent less adsorbent dose and contact time than other materials with a lead removal efficiency of 100%, it was a more potential adsorbent than other materials. Thus, adding iron(III) oxide-hydroxide and changing material form helped to improve material efficiencies for lead adsorption. The maximum adsorption capacities of SB, SBF, SBB, and SBFB were 6.161, 27.027, 23.697, and 57.471 mg/L, respectively by fitting the Langmuir model. Langmuir isotherm was best fitted for SB and SBB, whereas the Freundlich model was best fitted for SBF and SBFB. The pseudo-second-order kinetic model was best fitted for all materials. Moreover, all adsorbents could be reused for more than 5 cycles with the lead removal efficiency of more than 73%. Therefore, SBFB was potential material to further apply for lead removal in industrial applications.

Modeling the Biosorption Process of Heavy Metal Ions on Soybean-Based Low-Cost Biosorbents Using Artificial Neural Networks

Pollution of the environment with heavy metals requires finding solutions to eliminate them from aqueous flows. The current trends aim at exploiting the advantages of the adsorption operation, by using some low-cost sorbents from agricultural waste biomass, and with good retention capacity of some heavy metal ions. In this context, it is important to provide tools that allow the modeling and optimization of the process, in order to transpose the process to a higher operating scale of the biosorption process. This paper capitalizes on the results of previous research on the biosorption of heavy metal ions, namely Pb(II), Cd(II), and Zn(II) on soybean biomass and soybean waste biomass resulting from biofuels extraction process. The data were processed by applying a methodology based on artificial neural networks (ANNs) and evolutionary algorithms (EAs) capable of evolving ANN parameters. EAs are represented in this paper by the differential evolution (DE) algorithm, and a simultaneous training and determination of the topology is performed. The resulting hybrid algorithm, hSADE-NN was applied to obtain optimal models for the biosorption process. The expected response of the system addresses biosorption capacity of the biosorbent (q, mg/g), the biosorption efficiency (E, %), as functions of input parameters: pH, biosorbent dose (DS, mg/g), the initial concentration of metal in the solution (c0, mg/L), contact time (tc, h), and temperature (T, °C). Models were developed for the two output variables, for each metal ion, finding a high degree of accuracy. Furthermore, the combinations of input parameters were found which can lead to an optimal output in terms of biosorption capacity and biosorption efficiency.

Ecofriendly Biosorbents Produced from Cassava Solid Wastes: Sustainable Technology for the Removal of Cd2+, Pb2+, and Crtotal

This research is aimed at investigating the possible use of cassava agroindustry solid wastes in manufacturing adsorbents and their use in removing heavy metals Cd2+, Pb2+, and Crtotal from water. Thus, a pilot study was conducted in two main steps: (1) obtaining and characterizing the adsorbents and (2) laboratory studies focused on the evaluation of critical physicochemical parameters on adsorption, such as pH of the solution containing heavy metals, the effect of adsorbent dose, besides kinetics and equilibrium adsorption and desorption studies. Three adsorbents were studied, cassava barks, bagasse, and their mixture. SEM, FTIR, pHPZC, acid digestion, and chemical composition analysis were employed for adsorbent characterization. The pH of the contaminated solution was evaluated within 4.0 to 7.0, while the adsorbent doses varied from 5.0 to 24.0 g L-1. The adsorption kinetics was evaluated within 5 to 180 minutes and interpreted using pseudofirst- and second-order models. Finally, equilibrium and desorption studies were performed by evaluating adsorbent performance within 5 to 200 mg L-1 of heavy metals, using several nonlinear models for results interpretation. SEM analysis reveals a heterogeneous structure full of cavities. FTIR before and after adsorption reveals gaps related to missing functional groups, suggesting a significant role of alkenes, carboxylic acid, alcohol, anhydride, and ether. pHPZC is found at pH 6.02, 6.04, and 6.26 for adsorbents derived from barks, bagasse, and their mixture. In low concentrations of metals, the higher adsorption capacities were found at pH 7.0 (94.9%) using 16 g L-1 of adsorbent, with the most cost-benefit dose found using 8.0 g L-1. The removal of metals reaches equilibrium within 5-10 minutes of contact time with pseudosecond-order best adjustments to the observed phenomena. The adsorption of metals by a cassava adsorbent is better adjusted to the Freundlich model, with significant and critical information provided by Sips, Redlich-Peterson, Temkin, Liu, and Khan models. Adsorption/desorption studies indicate that cassava adsorbent performs, on average, -10% of the adsorption of metals compared to activated carbon. Nevertheless, factors such as low cost and availability favor the use of such natural materials.