Copper (II) is widely used in industrial processes, and even at low concentrations, it can be toxic to aquatic organisms and humans. “To ensure safety for human consumption and the environment, copper remediation technologies aim to meet the WHO permissible limit of 2.0 mg Cu/L for drinking water and the U.S. EPA maximum goal of 1.3 mg Cu/L, while also addressing the acute toxicity to fish that can occur even at small concentrations in natural water. Exceeding this limit poses risks to human health and the environment. Therefore, effective treatment of wastewater and soil contaminated with copper is essential to reduce these risks” [1]-[5]. “Biosorption is defined as the removal of heavy metal ions from aqueous solutions using living or dead, freely or immobilised biological materials” [3][6]. [7] “Biosorption method is particularly effective for treating wastewater with low metal concentrations (1 - 100 mg/L) where traditional methods are economically unviable” [3][8]-[12]. Copper (II) biosorption is an eco-friendly and cost-effective separation process that utilizes biological materials-such as bacteria, fungi, algae, and agricultural wastes-to remove or recover copper ions from aqueous environments.

“Copper uptake by Rhizopus arrhizusbiomass ranged between 50 and 150 mg/mL (de Rome and Gadd, 1987) [13] while the results by Preetha and Viruthagiri (2007) [14] recorded that under optimized process conditions (4.14 of pH, 37.75˚C of temperature, 53.84 mg/L of initial copper ion concentration, and 8.17 g/L of biomass loading) about 98.34% copper removal from aqueous solution can be achieved” [13][14].

“Biosorption is exhibited by bacteria, algae, fungi and yeasts. Not only living organisms, but also residuals of dead bodies of microorganisms shows biosorbent properties like agricultural wastes including husk, seeds, peels and stalks of different crops. Different factors affect the rate of biosorption which includes temperature, pH, nature of biosorbents, surface area to volume ratio, concentration of biomass, initial metal ion concentration and metal affinity to biosorbent. Various models including Freundlich model and Langmuir model can be used to describe biosorption. Recovery of biosorbed metals can be done using agents like thiosulfate, mineral acids and organic acids. Choice of desorption agent should be carefully selected to prevent alteration of physical properties of a biosorbent” [15]. “This technology is particularly valuable because copper is a heavy metal that is toxic to living organisms at elevated concentrations, causing health issues like liver and kidney damage, Wilson’s disease, and anemia” [16].

“Rhizopus arrhizus IMI 280098 was grown and maintained at 30˚C on GMY medium containing glucose (30 g/L), malt extract (10 g/L), yeast extract (10 g/L) and 1.2% agar for the solid medium. In order to obtain freely suspended cells, liquid medium was inoculated with Rhizopus arrhizus spore suspension in sterile distilled water at 0.5%(v/v) level. After cessation of growth, immobilized cultures were washed twice with double distilled water and then inactivated using 1% formaldehyde. This dead immobilized biomass was used for the removal of copper from solutions of 2 - 100 mg/L initial concentration. Copper solutions for biosorption experiments were prepared using (NO₃)₂. 3H₂O in double distilled water. Copper concentration was measured by an atomic absorption Spectrophotometer (AA, Model IL151, Instrumentation Laboratory NC, Massachusetts, USA). A 6-litre bioreactor was employed for the copper biosorption batch kinetic studies. Rhizopus arrhizus cells were immobilized naturally by physical entrapment within the open pore network of reticulated polyurethane foam (Declon, Corby, Northants, UK) or stainless-steel knitted mesh material (Knit Mesh Ltd, Surrey, UK). Immobilized biomass could be used as a technical adsorbent in the same way as granular carbon or nonexchange resins in a packed bed, a batch or continuous stirred tank reactor to separate metal ions from aqueous solutions” [3][17].

“Rhizopus arrhizus cell wall is approximately 90% polysaccharides, primarily composed of chitin, chitosan (polymers of N-acetyl D-glucosamine), mannans, and glucans. The wall contains various ligands that act as functional groups for metal binding, including carboxyl (-COOH), phosphate ( PO 4 3 − ), amino/amine (-NH), hydroxyl (-OH), and sulfhydryl (-SH) groups” [18]. Rhizopus arrhizus is a zygomycete fungus recognized for its rapid growth and resilience to acidic and oxidative conditions. Biomass is typically killed and stabilized using 1% formaldehyde. While living biomass can be used, dead (non-viable) biomass is often preferred for industrial applications because it requires no nutrient supply, is resistant to metal toxicity, and can be stored for long periods (up to 10 months). To enhance structural stability and reuse in bioreactors, cells are often immobilized within reticulated polyurethane foam or stainless-steel mesh. This creates a high-porosity mycelial mat permeable to the bulk liquid. Isotherm models describe the equilibrium relationship between the concentration of the metal in the aqueous phase and the amount of metal adsorbed on the biomass at a constant temperature. “Copper solutions for the biosorption experiments were prepared using distilled water and Cu (NO)₂·3H₂O (copper nitrate) from Fisons (AR grade). The pH of the synthetic solution was adjusted to 5.5 or 7.0 using 1 M KOH and 1 M HNO₃” [3].

“The actual wastewater samples were obtained from the Kidsgrove Sewerage Treatment Works located in the town of Kidsgrove, Manchester, England. The sample I (author) collected from Kidsgrove Sewerage Treatment Works the trade effluent as discharged to sewer from ICL’s factory in the town. A process which produces a copper bearing effluent. The bulk of the copper is removed by a treatment plant prior to discharge to enable ICL to meet the consent conditions laid down by North West Water Ltd. Since they had not analysed the sample supplied it could only be guessed as to what might have been presented in it. In such effluents, normally copper is in the range of 2 - 3 mg/L (measured as 3 mg/L) and there are probably lesser amounts of tin and lead, approximately 0.5 mg/l. The effluent has little organic strength, a COD of less than 100 mg/1 (measured as 90 mg/L), with only trace quantities of detergents, organic acids esters, alcohols and glycols which are used in some of their processes. There will also be inorganic salts, predominantly nitrate from the nitric acid for etching but also sulphates and chlorides (measured as 37 mg/L). pH of the effluent was 7.95. ICL’s effluent is mixed with domestic sewage and they are treated together at Kidsgrove Sewage Treatment Works. The works is a conventional activated sludge plant treating 7000 m³ per day. Sewage sludge, having been treated by an on—site digestion plant, is disposed of on farmland. The sample, taken from the influent of the advanced treatment plant, contains organic and inorganic pollutants at varying concentrations; this complex solution contains 3 mg/L of copper. Its pH is 7.95. Based on the sources, the removal efficiency for the real effluent was qualitatively described as high, even though the initial copper concentration was relatively low at 3 mg/L” [3].

The biosorption mechanism of copper by Rhizopus arrhizus is a complex, multi-stage process primarily involving passive physicochemical interactions with the fungal cell wall, although it can also involve active metabolic accumulation in living cells. In living systems, this stage includes active bioaccumulation, where metal ions penetrate the cell membrane and are transported into the intracellular space. The mechanism is generally categorized into the following stages and processes: Research indicates that copper uptake occurs in two distinct kinetic stages: Physical/Passive Sorption (Stage 1): This is a metabolism-independent, extremely rapid event where approximately 89% - 98% of total uptake occurs within the first 3 to 10 minutes. This phase is characterized by extracellular binding where copper ions interact with the cell wall surface through ion exchange, physical adsorption, and inorganic microprecipitation. Chemical/Biological Sorption (Stage 2): This is a slower phase (taking longer than 10 minutes) involving diffusion and chemical complexation.

“These factors explain why researchers observe a typical drop in uptake efficiency—approximately 25% between the first and third cycles in batch systems and 28% over six cycles in continuous bioreactors. In large-scale bioreactors, the biomass is often subjected to shear stress caused by agitation. For industrial viability, biosorbents must be regenerable. Desorbing agents such as 0.1 M HCl, 1 M HNO₃, or 0.1 M EDTA have shown up to approximately 90% - 100% recovery of bound copper, allowing materials like Rhizopus arrhizus to be reused for 3 (Batch Sheet Bioreactor, BSB) to 6 consecutive cycles (Continuous Sheet Bioreactor, CSB) with minimal loss (25% - 28%) in performance. The reduction in the accessibility of functional groups over several biosorption-desorption cycles is primarily caused by a combination of physical structural damage, chemical alterations from regeneration agents, and changes in the biomass’s surface area” [3][6][28]. Continuous Sheet Bioreactor (CSB) copper biosorption and desorption results (based on the initial biomass concentration) are shown in Figure 4Figure 4.

(Source: Author’s own elaboration).

Figure 4. Continuous Sheet Bioreactor (CSB) Copper Biosorption and Desorption Results (based on the initial biomass concentration). (Continuous Sheet Bioreactor experiment: pH = 5.5, T = 30˚C, C_b0 = 100 mg Cu/L; Agitation = 400 rpm, volume = 6 L, biosorbent = 5.45 g d.w./L, flow rate=100 mL/min, stainless steel sheets = 1.6 - 2.0 stitches per cm. (16x14x6x0.5 cm. sheets), Desorption: 0.1 M HCl.

Regeneration of exhausted biomass was possible by using 0.1 M HC1. Exhausted biomass can be regenerated using 0.1 M HCl, though uptake efficiency typically drops by approximately 25% between the first and third cycles in regeneration system in Batch Sheet Bioreactor (BSB). Research utilized Batch Sheet Bioreactors (BSB) and Continuous Sheet Bioreactors (CSB) to test Rhizopus arrhizus (immobilized dead biofilm, synthetic copper solutions) capacity. Saturation capacity is average 52 mg Cu (II)/g dry weight biosorbent for BSB, average 51 mg Cu (II)/g dry weight biosorbent for CSB bioreactors in optimum conditions. For industrial applications (real effluents), immobilized dead Rhizopus arrhizus in a BSB/CSB configuration is highly effective for removal of copper ions. The immobilized dead biomass maintains structural stability and significant functional capacity over multiple reuse cycles.

The overall uptake efficiency for the CSB system typically drops by approximately 28% between the first (59.7 mg Cu/g biomass)/and sixth cycles (42.7 mg Cu/g biomass). Despite this decline, the bioreactor maintains a high overall removal efficiency, generally ranging between 70% and 95%. The immobilised dead biomass could be used effectively in a 6-liter bioreactor continuously for at least 6 cycles of biosorption to exhaustion and then desorption with little change in the performance. The saturation uptake capacity for immobilised dead cells in the continuous system was initially 59.7 mg Cu (II)/g and after six cycles, 42.7 mg Cu (II)/g. Though uptake efficiency typically drops by approximately 28% between the first and sixth cycles in continuous sheet bioreactor (CBS) system. “Desorption studies have been performed to evaluate the regeneration potential of the selected biosorbents. Since acids are reported in the literature as the best eluents for desorption compared to other alternatives, a non-destructive method using nitric acid (0.1 M HNO₃ and 1 M HNO₃) and EDTA (0.1 M) was employed to conduct the desorption experiments. The desorption behavior confirms that the adsorption of copper ions involves reversible interactions, including ion exchange and coordination with the functional groups of the four biosorbents. This reversibility allows plant-based biosorbents to be efficiently regenerated and reused, enhancing their practicality and cost-effectiveness. From a practical and ecological perspective, EDTA is the preferred eluent. It is effective across all biosorbents while reducing the need for highly acidic conditions, making it a more environmentally friendly and less corrosive option for sorbent regeneration. The adsorption capacity of MO (Melissa officinalisL., plant material) decreases only slightly, from 82% in the first cycle to 77% in the fourth cycle. Meanwhile, the desorption capacity remains high, with 100% desorption efficiency for the first three cycles and 96% for the fourth cycle. These findings demonstrate that the studied plant-based materials are promising biosorbents due to their reversible adsorption mechanism, which is highly advantageous for applications in water purification and heavy metal recovery” [34].

“The capacity of dead waste sludge is highly sensitive to the pH of the solution (often optimal around pH 5.0 - 6.0 for cations) and the initial metal concentration. Additionally, chemically treated sludge (e.g., with sulphuric acid) generally exhibits higher capacities than untreated or formaldehyde-treated forms because the treatment can increase surface area and the accessibility of functional groups like carboxyl and amino groups” [3][19].

“Other sources mention that formaldehyde is also used to inactivate fungal biomass like Rhizopus arrhizus to improve structural stability and resistance to chemicals, allowing the dead biomass to be used for up to 10 months without losing its activity” [17].

“The pH of biosorbents is another critical factor influencing adsorption. The studied biosorbents have pH values ranging from 5.8 to 6.3. This near-neutral pH range makes the biosorbents suitable for use in environments where extreme pH conditions might otherwise limit their effectiveness. The acidity of the environment is a critical parameter in the biosorption process. It influences the chemical state of the active centers of the biosorbent, the form and concentration of metal ions in the solution, the surface charge of the biosorbent, and the tendency to form complexes” [34].

“The removal capacity exhibited a direct proportional relationship to pH elevation, achieving optimal performance at pH 7.0. At higher pH values, the removal capacity decreased significantly. The reason for such a situation might be that cell wall ligands exhibit a strong affinity for hydronium ions at lower pH values. Temperature plays a pivotal role in heavy metal removal by live biosorbents, as it directly influences biomass growth and metabolic activity. A decline in removal effectiveness may result from departures from the optimal temperature range. the removal capacity of strain ZC255 (Rossellomorea sp.ZC255) for Cu (II) increased as the temperature increased from 15˚C to 28˚C but declined at higher temperatures. The maximum removal capacity was 253.4 mg/g biomass under optimum conditions (pH 7.0, 28˚C, and 2% inoculation amount). Meanwhile, kinetic analysis confirmed that adsorption follows pseudo-second-order kinetics, indicating chemisorption as the dominant mechanism. Equilibrium isotherm studies revealed that adsorption behavior aligns with both the Langmuir (monolayer adsorption) and the Freundlich (heterogeneous surface) models, suggesting complex interactions between Cu (II) and bacterial surfaces” [51].

“This scientific paper examines the process of biosorption, which utilizes non-living biological matter to extract low-level pollutants like heavy metals from industrial wastewater. The researchers specifically investigated how dead Rhizopus arrhizus cells, trapped within foam or steel mesh structures, could effectively remove copper ions from a solution. Through repeated experimental cycles, the study demonstrates that these immobilized cells maintain high efficiency and stability over long periods, offering a cost-effective and renewable method for water purification. By applying mathematical models and testing various environmental conditions, the authors conclude that this biological approach provides a significant improvement for the recovery and removal of toxic contaminants in large-scale applications” [8][9].

“This research paper details the development of a mathematical model (the orthogonal collocation method) designed to simulate how dead immobilized biomass removes copper ions from wastewater within a batch bioreactor. By utilizing the fungus Rhizopus arrhizus trapped in porous foam or steel mesh sheets, the authors created a system where mass transfer and biosorption kinetics work together to decontaminate aqueous solutions. The study emphasizes that internal transport, involving both diffusion and convection through the biomass, is a critical factor in determining the efficiency of metal recovery. Through sensitivity analysis, the researchers demonstrated that variables such as initial metal concentration, biomass density, and mat thickness significantly influence the speed and capacity of the biosorption process. Ultimately, the work provides a theoretical framework for designing more effective industrial systems for heavy metal removal using biological adsorbents” [3][6][8][9][29].

The removal efficiency of dead Rhizopus arrhizus is characterized by high performance and rapid kinetics, particularly for heavy metals like copper. In synthetic solutions (10 mg/L initial concentration), freely dead Rhizopus arrhizus achieved a removal yield of 89% within the first 10 minutes and reached 98% at equilibrium (60 minutes). The saturation uptake capacity was found to be 40 - 94 mg Cu (II)/g dry weight for immobilised dead cells compared to 100 - 172 mg Cu (II)/g dry weight for freely suspended dead cells, ranges depending on the process parameters. Use of a real effluent reduced the biomass copper uptake capacity. The saturation uptake was found to be 23.4 mg Cu (II)/g dry weight for immobilised dead cells compared to 33.8 mg Cu (II)/g dry weight for freely suspended dead cells.

“Researchers employ isotherm models like Langmuir, Freundlich, and Sips to describe surface saturation” [36]. “Several studies report that the Freundlich model provides the best correlation for immobilized cells, often outperforming the Langmuir and BET models. The Freundlich isotherm model prediction far the immobilised cells was close to the Langmuir and BET models; however, the former gave a better correlation” [3][6][8][9].

Different biosorbents and adsorbents uptake capacities vary depending on the conditions. Based on the provided sources (see Table 3), the modified watermelon shell exhibits the highest recorded copper uptake capacity, reaching up to 357.14 mg Cu/g. Among specifically designated biological composites, the Algal-Fe₂O₃ nanoparticle composite follows with a maximum capacity of 297.7 mg Cu/g. For pure bacterial strains, Rossellomorea sp.ZC255 shows a high performance of 253.4 mg Cu/g under optimized conditions. The saturation uptake capacity was found to be 40 - 94 mg Cu (II)/g dry weight for immobilised dead cells compared to 100 - 172 mg Cu (II)/g dry weight for freely suspended dead cells ranges depending on the process parameters using shake flasks. Rhizopus arrhizus (immobilized living biomass) shows a lower capacity of 19.46 mg Cu/g compared to its dead forms. Rhizopus arrhizus (immobilized dead) in real wastewater effluents, the capacity drops significantly in complex solutions to 23.4 mg Cu/g. Dead biomass is highly resistant to metal toxicity, whereas living cells may be inhibited or killed by high concentrations of the heavy metals they are intended to remove. From a performance perspective, dead biomass typically exhibits significantly higher copper uptake capacities; for example, freely dead Rhizopus arrhizus can reach up to 172 mg Cu/g, while living forms of the same fungus typically range between 10.76 and 37.785 mg Cu/g. While biosorption is a highly efficient and cost-effective technology, its widespread industrial application is hindered by several significant technical, physical, and environmental challenges. Biosorption systems are highly sensitive to fluctuations in pH, temperature, and ionic strength, which can alter the structure of the sorbent or the chemical form of the metal ions. In multi-metal systems, the uptake of copper is generally reduced because various metal ions and other pollutants compete for the same non-specific functional groups (active binding sites) on the biosorbent’s surface. The presence of high total concentrations of various metal ions in real solutions leads to rapid saturation of the biosorbent. Copper (II) biosorption is an eco-friendly and cost-effective separation process that utilizes biological materials—such as bacteria, fungi, algae, and agricultural wastes—to remove or recover copper ions from aqueous environments. It notes that the process is used not only to remove toxic pollutants but also to recover valuable metal resources, aligning with sustainable industrial practices discussed in this critical review.

The conclusions reached in this work can be listed as follows:

Copper (II) is toxic heavy metal to aquatic organisms even at low levels (1 - 100 mg/L); found in shellfish, liver, and mushrooms.Biosorption is defined as the removal of heavy metal ions from aqueous solutions using living or dead, freely or immobilised biological materials. Biosorption method is particularly effective for treating wastewater with low metal concentrations (1 - 100 mg/L) where traditional methods are economically unviable.Copper (II) biosorption is an eco-friendly and cost-effective separation process that utilizes biological materials-such as bacteria, fungi, algae, and agricultural wastes-to remove or recover copper ions from aqueous environments.Rhizopus arrhizus is a zygomycete fungus recognized for its rapid growth and resilience to acidic and oxidative conditions. Rhizopus arrhizus (from the order Mucorales) was selected for its wide surface area, high hanging capacity, and harmlessness to humans.There is very little difference between the growth patterns of immobilised and freely suspended Rhizopus arrhizus,showing that the method of immobilisation has no detrimental effect.Rhizopus arrhizus immobilised in reticulated polyurethane foam and stainless-steel knitted mesh sheets can be used for the removal of copper from aqueous solutions.Grown at 30˚C, inactivated (using formaldehyde or sulfuric acid), and dried to a concentration of 4.3 g dry weight R.arrhizus/L for experimental use.Used in its dead form to avoid the need for continuous nutrient addition, which would otherwise increase Biological Oxygen Demand (BOD) or Chemical Oxygen Demand (COD).The stability of the dead immobilised Rhizopus arrhizus was tested by storing at room temperature in formaldehyde over a period of at least 10 months and it was found that the immobilised cells did not lose their biosorption activity.Dead immobilised biomass can be used for the removal of copper from solutions of 1 - 100 mg/1 initial concentration.Studies show that biosorption is a two-stage process: Physical Stage: Rapid (3 - 10 minutes), involving ion exchange and micro-precipitation at the surface. Chemical/Biological Stage: Slower (>10 minutes), involving diffusion and complexation. The Pseudo-second order rate model typically provides the highest correlation coefficients, suggesting that the rate-limiting step is chemisorption involving valency forces through electron sharing.Repeated batch runs were also performed and it was found that the immobilised dead cells could be repeatedly used for 250 successive batches using shake flasks.The saturation uptake capacity was found to be 40 - 94 mg Cu (II)/g dry weight for immobilised dead cells compared to 100 - 172 mg Cu (II)/g dry weight for freely suspended dead cells, ranges depending on the process parameters using shake flasks.Regeneration of exhausted biomass was possible by using 0.1 M HC1. Exhausted biomass can be regenerated using 0.1 M HCl, though uptake efficiency typically drops by approximately 25% between the first and third cycles in regeneration system in Batch Sheet Bioreactor (BSB).Research utilized Batch Sheet Bioreactors (BSB) and Continuous Sheet Bioreactors (CSB) to test Rhizopus arrhizuscapacity. Saturation capacity is average 52 mg Cu (II)/g dry weight biosorbent for both bioreactors in optimum conditions. For industrial applications (real effluents), Rhizopus arrhizus in a BSB/CSB configuration is highly effective for copper.The immobilised dead biomass could be used effectively in a 6-liter bioreactor continuously for at least 6 cycles of biosorption to exhaustion and then desorption with little change in the performance. The saturation uptake capacity for immobilised dead cells in the continuous system was initially 59.7 mg Cu (II)/g and after six cycles, 42.7 mg Cu (II)/g. Though uptake efficiency typically drops by approximately 28% between the first (59.7) and sixth cycles (42.7) in continuous sheet bioreactor (CBS) system. MATLAB is essential for solving complex mathematical frameworks that couple biosorption kinetics with mass transfer. The immobilised fungal sorption isotherm is a favourable type. The Freundlich model (immobilized dead Rhizopus arrhizus) prediction (the orthogonal collocation method) [3][17], was close to the Langmuir, BET and Sips (Langmuir-Freundlich hybrid) models however, the Sips gave a little better correlation by MATLAB analysis [19]19] for freely suspended dead Rhizopus arrhizus. The Sips (Langmuir-Freundlich hybrid) model has also been identified for freely suspended dead Rhizopus arrhizusbiosorption of copper a superior fit, yielding an R² of 0.9931. It is used to solve the partial and first-order differential equations resulting from steady-state mass balances.It employs techniques such as the orthogonal collocation method [3][17] and the fourth-order Runge-Kutta method [19] to simulate concentration profiles over time in bioreactors. Used the orthogonal collocation method to predict copper concentration profiles in the bulk liquid, showing how the system parameters affect biosorption performance.When initial copper concentration increased the removal efficiency decreased.Removal of copper from the solution was more efficient with increasing pH.The amount of copper adsorbed per unit weight was maximal at lower biomass concentrations and decreased with increasing concentrations of biomass.The saturation capacity depends on the state of the biomass and the type of solution. Free dead Rhizopus arrhizus demonstrated the highest capacity in synthetic solutions at 100 - 172 mg Cu²⁺/g and in real industrial wastewater, this dropped to 33.8 mg/g. Immobilized dead Rhizopus arrhizus are capacities in synthetic solutions ranged from 40 to 94 mg/g, and dropped to 23.4 mg/g in real industrial effluents. The real effluent sample, taken from the influent of the advanced treatment plant, contains organic and inorganic pollutants at varying concentrations; this complex solution contains 3 mg/L of copper. Its pH is 7.95. Real effluent also includes amounts of tin and lead, approximately 0.5 mg/L, chlorides as 37 mg/L and COD as 90 mg/L. Use of a real effluent reduced the biomass copper uptake capacity. The saturation uptake was found to be 23.4 mg Cu (II)/g dry weight for immobilised dead cells compared to 33.8 mg Cu (II)/g dry weight for freely suspended dead cells.The high elution efficiency (up to 94% - 100%) using 0.1 M HCl confirms that immobilized dead Rhizopus arrhizus is a highly durable and regenerable biosorbent for laboratory and industrial copper removal possible applications.The results have shown that immobilised dead Rhizopus arrhizus can successfully remove copper from aqueous solution.“Biosorption systems are often highly sensitive to environmental changes, such as fluctuations in pH, temperature, and ionic strength, which can alter the sorbent structure or metal speciation” [3][10][12][17][73].

A list of suggestions for further research prompted by the work presented in this study can be listed as follows:

Biosorption reactor system should be applied for real effluent treatment for in larger systems in real life.Immobilised or freely dead biomass should be produced from domestic, agricultural or industrial waste biomass for it to be a more applicable, reasonable, economic, cheaper, competitive, sustainable and ecofriendly biosorbent.Biosorption reactor studies performed have utilized a single 6-liter bioreactor in studies. Investigations should be performed to elucidate the possible advantages that could be obtained from the use of bioreactors in series in larger systems for improved removal efficiency for conforming to standards irrigation or process water.Biosorption methods should be usable as an alternative and competitive for the recovery of rare earth elements and valuable elements. In this regard, laboratory researches should not be limited; additional field studies should be increased. The transition from laboratory modeling to real-world application should be demonstrated through both industrial bioreactors and portable community filters.

The article is single-authored. No potential conflict of interest was reported by the author(s).

The author stated that this study did not require ethical approval or informed consent because it reviewed existing literature and did not involve new data collection from human participants.

The author stated that control of English language has been used DeepL Translator (pro version, fee paid).

All data generated from open access literature and this study and analysed during this study are available for sharing when appropriate request is directed to the author.