Optimization of the use of a biosorbent to remove heavy metals: Regeneration and reuse of exhausted biosorbent

Pharmaceutical Pollutants: Ecotoxicological Impacts and the Use of Agro-Industrial Waste for Their Removal from Aquatic Environments

Medicines are pharmaceutical substances used to treat, prevent, or relieve symptoms of different diseases in animals and humans. However, their large-scale production and use worldwide cause their release to the environment. Pharmaceutical molecules are currently considered emerging pollutants that enter water bodies due to inadequate management, affecting water quality and generating adverse effects on aquatic organisms. Hence, different alternatives for pharmaceuticals removal from water have been sought; among them, the use of agro-industrial wastes has been proposed, mainly because of its high availability and low cost. This review highlights the adverse ecotoxicological effects related to the presence of different pharmaceuticals on aquatic environments and analyzes 94 investigations, from 2012 to 2024, on the removal of 17 antibiotics, highlighting sulfamethoxazole as the most reported, as well as 6 non-steroidal anti-inflammatory drugs (NSAIDs) such as diclofenac and ibuprofen, and 27 pharmaceutical drugs with different pharmacological activities. The removal of these drugs was evaluated using agro-industrial wastes such as wheat straw, mung bean husk, bagasse, bamboo, olive stones, rice straw, pinewood, rice husk, among others. On average, 60% of the agro-industrial wastes were transformed into biochar to be used as a biosorbents for pharmaceuticals removal. The diversity in experimental conditions among the removal studies makes it difficult to stablish which agro-industrial waste has the greatest removal capacity; therefore, in this review, the drug mass removal rate (DMRR) was calculated, a parameter used with comparative purposes. Almond shell-activated biochar showed the highest removal rate for antibiotics (1940 mg/g·h), while cork powder (CP) (10,420 mg/g·h) showed the highest for NSAIDs. Therefore, scientific evidence demonstrates that agro-industrial waste is a promising alternative for the removal of emerging pollutants such as pharmaceuticals substances.

Synthesis of a novel functionalized biosorbent from mango stone and its application in the pharmaceutical's removal from water and a synthetic mixture

This paper explores the feasibility of functionalizing mango stones with iron oxide magnetic nanoparticles (MS-Fe3O4) by coprecipitation in batch adsorption processes. The synthesized material was characterized and applied in chloroquine (CQN) and sertraline hydrochloride (SER) removal from contaminated waters. The biosorbent was subjected to a regenerative study and treatment using a synthetic mixture of contaminants to evaluate its applicability in real effluents. The biosorbent was analyzed by transmission electron microscopy images, scanning electron microscopy, dispersive X-ray spectroscopy, Fourier transform infrared spectra, and zeta potential to characterize its chemical and morphology properties. The techniques applied showed the effectiveness of the proposed modification. In the adsorption experiments, the optimal adsorbent dosage was 0.01 g for both contaminants. The pH strongly influenced the adsorption of the drugs on MS-Fe3O4, and the best results were obtained in the pH range of 5-6. Kinetic data showed a better fit to the pseudo-second-order model, and the equilibrium time was achieved in 16 h for CQN and 4 h for SER. Isotherm studies revealed maximum adsorptive capacities of 49.42 and 64.79 mg g-1, respectively, for CQN and SER, at 318 K, demonstrating that the increase in temperature is a favorable factor, and the Sips model better describes the process. The thermodynamic parameters indicate an endothermic (ΔH° >0), spontaneous (ΔG° <0), and reversible (ΔS° >0) nature of the adsorption. This process is essentially governed by physical forces, such as hydrogen and π-π bonds. However, it is also valid to consider the presence of electrostatic forces due to the ionizing nature of CQN and SER. The MS-Fe3O4 biosorbent showed good performance when evaluated in a synthetic mixture of four contaminants, with an overall removal efficiency of approximately 86% and the regenerative capacity of three reusing cycles.

Pitahaya Fruit (Hylocereus spp.) Peels Evaluation for Removal of Pb(II), Cd(II), Co(II), and Ni(II) from the Waters

The present study investigated the performance of Pitahaya (Hylocereus spp.) peel (PP) as a low-cost biosorbent in the removal of Co(II), Cd(II), Pb(II), and Ni(II) from single and multi-component solutions. The characterization of the samples was carried out by pHpzc, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Biosorption was carried out by batch experimental procedure to examine the effects of contact time, solution pH, initial concentration of metal ions, and biosorbent dosage. The results indicate that the biosorption of Pb(II), Cd(II), Co(II), and Ni(II) Pitahaya peels followed pseudo-second-order kinetics, and equilibrium adsorption followed the Langmuir model. The maximum sorption capacities of PP for the metallic species were found to be as follows: Pb (82.64 mg g−1) > Cd (17.95 mg g−1) > Co (6.013 mg g−1) > Ni (5.322 mg g−1). However, the efficiency of the biosorption change when the metallic species are mixed. The re-generation of the PP after the adsorption of the metallic species was done using 0.1 M HNO3 solution, and the reusability of the biomass was carried out using two adsorption and desorption cycles.

Adsorption of Toxic Zinc by Functionalized Lignocellulose Derived from Waste Biomass: Kinetics, Isotherms and Thermodynamics

Heavy metals pollution receives worldwide attention due to great toxicity, significant bio-accumulation and non-biodegradability. Adsorption is a promising technique for removing heavy metals from wastewater. Adsorption of zinc (Zn(II)) from aqueous solution was investigated by functionalized lignocellulose derived from fallen leaves. Alkalized lignocellulose (AC), xanthated lignocellulose (XC) and carboxylated lignocellulose (CC) were characterized by Fourier transform infrared spectrum (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The effect of sorbent dosage, solution pH, sorption time and initial Zn(II) concentration on Zn(II) sorption was investigated by single-factor experiment. Sorption kinetics, isotherms and thermodynamics were examined to reveal sorption mechanism. The sorption capacity and removal rate remarkably depend on experimental variables. Zn(II) sorption onto AC, XC and CC is well described by the pseudo second order kinetics and Langmuir isotherm. The sorption process is fast, reaching sorption equilibrium at 30 min. The maximum sorption capacity of Zn(II) onto CC is 46.49 mg/g, higher than that onto AC, XC and other reported sorbents. Thermodynamic parameters indicate that Zn(II) sorption is a spontaneous process. Sorption mechanism is majorly attributed to surface complexation. This work shows the feasibility of removing toxic Zn(II) from aqueous solution by locally available biomass, providing a sustainable approach for wastewater treatment.

Mechanisms of halosulfuron methyl pesticide biosorption onto neem seeds powder

The current investigation was designed to remove halosulfuron methyl from aqueous media by means of neem seed powder (NSP) in batch modes. Characterizations of NSP were carried out by using EDX, SEM, FTIR, point of zero charge and surface analysis. Optimum operation conditions were scrutinized by studying the influence of different factors like solution pH, dose of NSP, contact time, initial halosulfuron methyl concentration and temperature. Result indicates the dependency of the removal of halosulfuron methyl on solution pH and maximal removal (54%) was achieved in acidic medium (i.e. pH 3.0). To identify the chemical surface of NSP, point of zero charge of NSP was determined and was found to be 6.5 which imply that the surface of NSP is positively charged below pH 6.6 and favored the anionic sorption. Kinetics of halosulfuron methyl were demonstrated well by pseudo second order due to highest R2 (0.99) owing to the nearness between experimental and calculated sorption capacities. Isotherm results imply that Langmuir was found to the principal model to explain the removal of halosulfuron methyl and maximum monolayer sorption capacity was determined to be 200 mg g-1. Thermodynamic parameters like ΔH°, ΔG° and ΔS° were calculated from van't Hoff plot and were found negative which suggest that removal of halosulfuron methyl is exothermic and spontaneous at low temperature. These outcomes insinuate that neem seed power may be a valuable, inexpensive and ecofriendly biosorbent for the removal of pesticides.

Biosorption of Co2+ Ions from Aqueous Solution by K2HPO4-Pretreated Duckweed Lemna gibba

The wastewater of the many industries that use divalent cobalt (Co2+)-containing compounds has elevated levels of this metal. Thus, novel technology is needed to efficiently remove Co2+ ions from aqueous solutions. Biosorption is a low-cost technique capable of removing heavy metals from contaminated water. This study aims to evaluate the performance of KH2PO4-pretreated Lemna gibba (PLEM) as a biosorbent of Co2+ in aqueous solutions tested under different conditions of pH, particle size, and initial Co2+ concentration. Kinetic, equilibrium, and thermodynamic studies were conducted. The capacity of biosorption increased with a greater initial Co2+ concentration and was optimal at pH 7.0 and with small-sized biosorbent particles (0.3–0.8 mm). The pseudo-second-order sorption model best describes the experimental data on Co2+ biosorption kinetics. The Sips and Redlich-Peterson isotherm models best predict the biosorption capacity at equilibrium. According to the thermodynamic study, biosorption of Co2+ was endothermic and spontaneous. The effect of pH on the biosorption/desorption of Co2+ suggests that electrostatic attraction is the main biosorption mechanism. SEM-EDX verified the presence of Co2+ on the surface of the pretreated-saturated biosorbent and the absence of the metal after desorption.

Continuous dye adsorption and desorption on an invasive macrophyte (Salvinia minima)

The continuous adsorption-desorption of methylene blue (MB) on an invasive macrophyte, Salvinia minima, was investigated in fixed-bed columns. The effects of bed depth (h) (9.30, 18.70, and 28 cm), inlet dye concentration (C₀) (51 ± 1.20, 154 ± 2.00, and 250 ± 1.50 mg L^-1), and flow rate (Q) (7 and 14 mL min^-1) on dye removal and breakthrough curves were assessed. Thomas, modified dose-response (MDR) and bed depth service time (BDST) models were fitted to the experimental data. Desorption and regeneration studies were also performed. The breakthrough time was affected by h, C₀, and Q. The dynamic bed capacity at the breakthrough point (q_b) increased with increasing h but decreased with increasing C₀ and Q. Dynamic bed capacities (q_e) from 318 to 322 mg g^-1 were achieved at h = 28 cm, C₀ = 154 ± 2.0, or 250 ± 1.50 mg L^-1, independently of the Q value. High MB removals were also observed (75-78%). FTIR analysis revealed that hydroxyl and carboxyl groups could be involved in dye adsorption. MDR and BDST models were both successfully used to predict the breakthrough curves of MB adsorption onto S. minima. A high regeneration efficiency (> 87%) was obtained after three adsorption-desorption cycles. These results confirm that the use of S. minima biomass could be a very efficient and eco-friendly alternative for MB adsorption in continuous mode.

Neural fuzzy modelization of copper removal from water by biosorption in fixed-bed columns using olive stone and pinion shell

Continuous copper biosorption in fixed-bed column by olive stone and pinion shell was studied. The effect of three operational parameters was analyzed: feed flow rate (2-6 ml/min), inlet copper concentration (40-100 mg/L) and bed-height (4.4-13.4 cm). Artificial Neural-Fuzzy Inference System (ANFIS) was used in order to optimize the percentage of copper removal and the retention capacity in the column. The highest percentage of copper retained was achieved at 2 ml/min, 40 mg/L and 4.4 cm. However, the optimum biosorption capacity was obtained at 6 ml/min, 100 mg/L and 13.4 cm. Finally, breakthrough curves were simulated with mathematical traditional models and ANFIS model. The calculated results obtained with each model were compared with experimental data. The best results were given by ANFIS modelling that predicted copper biosorption with high accuracy. Breakthrough curves surfaces, which enable the visualization of the behavior of the system in different process conditions, were represented.

Combustion of a Pb(II)-loaded olive tree pruning used as biosorbent

The olive tree pruning is a specific agroindustrial waste that can be successfully used as adsorbent, to remove Pb(II) from contaminated wastewater. Its final incineration has been studied in a thermobalance and in a laboratory flow reactor. The study aims at evaluating the fate of Pb during combustion, at two different scales of investigation. The flow reactor can treat samples approximately 10(2) larger than the conventional TGA. A detailed characterization of the raw and Pb(II)-loaded waste, before and after combustion is presented, including analysis of gas and solids products. The Pb(II)-loaded olive tree pruning has been prepared by a previous biosorption step in a lead solution, reaching a concentration of lead of 2.3 wt%. Several characterizations of the ashes and the mass balances proved that after the combustion, all the lead presents in the waste remained in ashes. Combustion in a flow reactor produced results consistent with those obtained in the thermobalance. It is thus confirmed that the combustion of Pb(II)-loaded olive tree pruning is a viable option to use it after the biosorption process. The Pb contained in the solid remained in the ashes, preventing possible environmental hazards.