Zinc and cadmium removal by biosorption on Undaria pinnatifida in batch and continuous processes

Role of Organic Fertilizer in the Transfer of Lead to Vegetables Produced in Tropical Mountain Agroecosystems

Understanding the relationship between the aerobic transformation of organic matter (OM) and the bioavailability of lead to plants may allow the safe application of organic fertilizers (OF) in agriculture. The present study aimed to elucidate the relationship of different OM structures with Pb, revealing the action of OF (poultry litter) on Pb dynamics, presenting the effects of OM transformations on bioavailability and transfer to vegetables produced in tropical mountain agroecosystems (TMA). The association of Pb with hydrophilic structures (CAlk-O and CAlk-di-O) during the aerobic transformation of poultry litter (PL) contributes to the increase in the water-soluble form of this metal (3.17-15.30%). The structural changes promoted by the transformation of OM, in addition to reducing the adsorption capacity of Pb in PL (Kd reduction from 1135.50 to 87.49), favor the formation of outer-sphere complexes. PL that have a more labile structure, i.e., those that are less humified, have greater affinity for Pb. The greater affinity of Pb for labile structures that are preserved in PL during OM transformations contributed to its increase and transport to edible plant parts. Considering the edible parts of vegetables grown in TMA and fertilized with fresh PL, 100% of broccoli, 91.78% of cabbage, 80.00% of tomato, 65.96% of parsley, 49.19% of lettuce, and 32.88% of cauliflower showed Pb contamination that exceeded the permitted level. Therefore, OF contributes to lead contamination of food produced in TMA, representing a risk to human health. Studies are needed to propose additional treatments for this residue before its use.

Controlling factors of heavy metal(loid) accumulation in rice: Main and interactive effects

Identifying the key determinants of heavy metal(loid) accumulation in rice and quantifying their contributions are critical for precise prediction of heavy metal(loid) concentrations in rice and the formulation of effective pollution control strategies. The accumulation of heavy metal(loid)s in rice can be influenced by both natural and anthropogenic factors, which may interact with each other. However, distinguishing the independent roles (main effects) from interactive effects and quantifying their impacts separately pose challenges. To address this knowledge gap, we employed TreeExplainer-based SHAP and random forest algorithms in this study to quantitatively estimate the primary influencing factors and their main and interactive effects on heavy metal(loid)s in rice. Our findings reveal that soil cadmium (SCd) and rice cultivation time (C_TIME) were the primary contributors to rice cadmium (RCd) and rice arsenic (RAs), respectively. Soil lead (SPb) and sampling distances from roads significantly contributed to rice lead (RPb). Additionally, we identified significant interactive effects of SCd and C_TIME, C_TIME and RCd, and RCd and rice variety on RCd, RAs, and RPb, respectively, emphasizing their significance. These insights are pivotal in improving the accuracy of heavy metal(loid) concentration predictions in rice and offering theoretical guidance for the formulation of pollution control measures.

Plummeting toxic contaminates from water through phycoremediation: Mechanism, influencing factors and future outlook to enhance the capacity of living and non-living algae

Freshwater habitats hold a unique role in the survival of all living organisms and supply water for drinking, irrigation, and life support activities. In recent decades, due to anthropogenic activities, deterioration in the water quality has been a long-lasting problem and challenge to the scientific fraternity. Although, these freshwater bodies have a bearable intrinsic capacity for pollution load however alarming increase in pollution limits the intrinsic capacities and requires additional technological interventions. The release of secondary pollutants from conventional interventions further needs revisiting the existing methodologies and asking for green interventions. Green interventions such as phycoremediation are natural, eco-friendly, economic, and energy-efficient alternatives and provide additional benefits such as nutrient recovery, biofuel production, and valuable secondary metabolites from polluted freshwater bodies. This systemic review in a nut-shell comprises the recent research insights on phycoremediation, technological implications, and influencing factors, and further discusses the associated mechanisms of metal ions biosorption by living and non-living algae, its advantages, and limitations. Besides, the article explores the possibility of future research prospects for applicability at a field scale that will help in the efficient utilization of resources, and improved ecological and health risks.

Comparison of Heavy Metals and Arsenic Species in Seaweeds Collected from Different Regions in Korea

We evaluated the levels of heavy metals and arsenic (As) species in 11 different types of seaweed collected from major coastal cities in Korea. The concentration ranges of heavy metals in the seaweed were as follows: cadmium (0.023–0.232 mg/kg fresh weight [fw]), and lead (0.025–0.222 mg/kg fw), with most meeting international regulations for edible seaweeds. The amount of total As, however, was high, ranging from 1.020 to 20.525 mg/kg fw. Especially in the case of Sargassum seaweed, the fraction of inorganic As, including arsenate (As [V]) and arsenate (As [III]), which have potent toxicity, ranged from 5.198 to 16.867 mg/kg fw, while other seaweeds, such as Pyropia sp., Enteromorpha sp., Undaria sp., and Saccharina sp., predominantly contained a non-toxic organic As (i.d. arsenosugars). Multivariate analysis revealed that the Sargassum genus group had high levels of inorganic As. Sargassum seaweeds had a high fraction of inorganic As, but most of them are considered inedible seaweeds. Of these, Sargassum fusiforme (hijiki) is widely recognized as an edible seaweed, but the average daily intake is quite low based on statistical data from Asian countries and S. fusiforme is considered a safe food when eaten at the recommended daily intake.

Invasive plants as biosorbents for environmental remediation: a review

Water contamination is an environmental burden for the next generations, calling for advanced methods such as adsorption to remove pollutants. For instance, unwanted biowaste and invasive plants can be converted into biosorbents for environmental remediation. This would partly solve the negative effects of invasive plants, estimated at 120 billion dollars in the USA. Here we review the distribution, impact, and use of invasive plants for water treatment, with emphasis on the preparation of biosorbents and removal of pollutants such as cadmium, lead, copper, zinc, nickel, mercury, chromate, synthetic dyes, and fossil fuels. Those biosorbents can remove 90-99% heavy metals from aqueous solutions. High adsorption capacities of 476.190 mg/g for synthetic dyes and 211 g/g for diesel oils have been observed. We also discuss the regeneration of these biosorbents.

Gallium-binding peptides as a tool for the sustainable treatment of industrial waste streams

Here we provide a proof of principle for an application-oriented concept for the peptide-based recovery of gallium in industrial wastewater, which was supported by biosorption studies with a real wastewater sample. We investigated the interaction of the gallium-binding peptides TMHHAAIAHPPH, NYLPHQSSSPSR, SQALSTSRQDLR, HTQHIQSDDHLA, and NDLQRHRLTAGP with gallium and arsenic through different experimental and computational approaches. Data obtained from isothermal titration microcalorimetry indicated a competitive influence by the presence of acetate ions with an exothermic contribution to the otherwise endothermic peptide gallium interactions. For peptide HTQHIQSDDHLA, a stabilizing influence of acetate ions on the metal peptide interaction was found. Peptide NYLPHQSSSPSR showed the highest affinity for gallium in ITC studies. Computational modeling of peptide NYLPHQSSSPSR was used to determine interaction parameters and to explain a possible binding mechanism. Furthermore, the peptides were immobilized on polystyrene beads. Thus, we created a novel and exceptionally robust peptide-based material for the biosorption of gallium from an aqueous solution. Data obtained from isothermal titration microcalorimetry indicated a competitive influence by the presence of acetate ions with an exothermic contribution to the otherwise endothermic peptide gallium interactions. For peptide HTQHIQSDDHLA, a stabilizing influence of acetate ions on the metal peptide interaction was found. Peptide NYLPHQSSSPSR showed the highest affinity for gallium in ITC studies. Computational modeling of peptide NYLPHQSSSPSR was used to determine interaction parameters and to explain a possible binding mechanism. Furthermore, the peptides were immobilized on polystyrene beads. Thus, we created a novel and exceptionally robust peptide-based material for the biosorption of gallium from an aqueous solution.

Analysis of Minerals and Heavy Metals Using ICP-OES and FTIR Techniques in Two Red Seaweeds (Gymnogongrus griffithsiae and Asparagopsis taxiformis) from Tunisia

In this study, the mineral and heavy metals (arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), potassium (K), manganese (Mn), sodium (Na), phosphorus (P), and lead (Pb)) in two red Tunisian seaweeds Gymnogongrus griffithsiae (G. griffithsiae) and Asparagopsis taxiformis (A. taxiformis), were evaluated. Mineral and trace element analyses were achieved using inductively coupled plasma optical emission spectrometry (ICP-OES). Fourier transform infrared (FTIR) spectroscopy was used to predict the major functional groups that would be implicated in the seaweeds mineral uptake. Our results showed that the studied A. taxiformis species had much higher mineral and heavy metal concentrations than G. griffithsiae. Na (200.60 mg/kg) was the most abundant element followed by K (137.84 mg/kg) > P (35.93 mg/kg) for A. taxiformis species. However, only Na (165.23 mg/kg) and P (51.19 mg/kg) were detected in G. griffithsiae alga. As regards heavy and toxic metals, allowable concentrations have been found in both seaweeds. The concentration ranges for the most undesirable heavy metals were as follows: Pb (0.39-0.51 mg/kg), As (0.11-0.40 mg/kg), Cd (0.01-0.02 mg/kg), and Hg (0.00-0.02 mg/kg). According to FTIR analysis, the major functional groups present in the studied seaweeds were carboxyl, hydroxyl, sulfate, and phosphate groups that are considered as excellent binding sites for metal retention.

Mercury interactions with algal and plastic microparticles: Comparative role as vectors of metals for the mussel, Mytilus galloprovincialis

The adsorption and desorption of Hg onto and from microplastics (MP) and microalgae (MA) were investigated, and fitted using pseudo-first-order and pseudo-second order kinetics models. Then, the potential role of MP as vector for the entrance and accumulation of Hg (MP-Hg) in comparison to natural pathways (via MA -MA-Hg-, and dissolved -WB-Hg-) was investigated in mussel. Mussels were exposed to a single dose of Hg (2375 ng ind^-1) for 4 h. Although the clearance of MP-Hg was relevant (82 %), it was lower than that of MA (95 %) and MA-Hg (94 %). The amount of the Hg accumulated and eliminated was higher in mussels exposed to MP-Hg (1417 ng Hg) than in those exposed to MA-Hg (882 ng Hg) and WB-Hg (1074 ng Hg). However, Hg accumulation was similar in the three mussel groups (≈800 ng Hg). This was related to the fast elimination of Hg still attached to MP by MP-Hg mussels. Hg was mainly accumulated in digestive gland in MA-Hg and MP-Hg mussels, and in gills in WB-Hg mussels. Overall, the results indicated that MP facilitated the entrance of Hg in mussel but also promoted Hg elimination, which could limit the toxicological risk of Hg adsorbed onto MP.

Proximal Composition of Undaria pinnatifida from San Jorge Gulf (Patagonia, Argentina)

Undaria pinnatifida is a brown macroalga considered a high quality natural food because of its numerous health benefits. The aim of this paper is to provide seasonal information on the chemical content of blades and sporophylls of U. pinnatifida from San Jorge Gulf (SJG, Chubut, Argentina) in order to evaluate their different uses. Moreover, samples of algae deposited on the beach are also studied. A multi-elemental analysis is made by Total Reflection X-ray Fluorescence (TXRF). Sixteen elements are quantified: As, Br, Ca, Cr, Cu, Fe, K, Mn, Ni, P, Pb, Rb, S, Sr, V and Zn. The results reveal that the mineral content in blades of U. pinnatifida is high, especially in autumn. Some elements show an important seasonal variation, such as: K (14-54.8 g kg-1), P (2.7-7.0 g kg-1), Sr (361-569 mg kg-1), Fe (62-140 mg kg-1), Zn (8-103 mg kg-1), Br (45-94 mg kg-1) and Rb (4-24 mg kg-1). In the case of potentially toxic elements, a variation was seen mainly in arsenic, with higher values during summer and autumn. The concentrations of nickel and lead are below the limit of detection (0.9 mg kg-1). Sporophylls contain high concentrations of macro and micronutrients, with maximum values in spring. Besides, reproductive structures showed higher total arsenic values than blades. This could indicate that arsenic is mainly accumulated in sporophylls. Algae deposited on the beach are considered a waste; but they show a similar elemental composition to the samples extracted from the sea. We concluded that all samples analyzed could be used as food or fertilizers by local populations.

Silica-Coated Magnetic Nanocomposites for Pb2+ Removal from Aqueous Solution

Magnetic iron oxide-silica shell nanocomposites with different iron oxide/silica ratio were synthesized and structurally characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), small-angle neutron scattering, magnetic and N2-sorption studies. The composite that resulted with the best properties in terms of contact surface area and saturation of magnetization was selected for Pb2+ adsorption studies from aqueous media. The material presented good absorption capacity (maximum adsorption capacity 14.9 mg·g−1) comparable with similar materials presented in literature. Its chemico-physical stability and adsorption capacity recommend the nanocomposite as a cheap adsorbent material for lead.

Characterization and mechanism of lead and zinc biosorption by growing Verticillium insectorum J3

Verticillium insectorum J3 was isolated from a local lead-zinc deposit tailing, and its biosorption characteristics and reaction to the toxicities of different Pb(II) and Zn(II) concentrations were investigated. SEM, FTIR, a pH test and a desorption experiment were carried out to identify a possible mechanism. The biosorption of J3 presented an inhibition trend at low concentrations (25-75 mg L-1) and promotion at high concentrations (100-300 mg L-1). J3 absorbed Pb(II) prior to Zn(II) and produced alkaline substances, while mycelial and pellet morphology modifications were important for the removal of Pb(II) and Zn(II) under different stressful conditions (SEM results). Both intracellular accumulation and extracellular absorption may contribute to the removal of Pb(II) at lower concentrations (25-50 mg L-1), although mainly extracellular biosorption occurred at higher concentrations (75-300 mg L-1). However, Zn(II) bioaccumulation occurred at all concentrations assayed. Verticillium insectorum J3 may have evolved active defenses to alleviate the toxicity of heavy metals and proved to be a highly efficient biosorbent, especially for Pb(II) at high concentrations. This study is a useful reference for the development of biotreatment technologies to mitigate heavy metal waste.

Biosorptive removal of Zn(II) ions by Pongamia oil cake (Pongamia pinnata) in batch and fixed-bed column studies using response surface methodology and artificial neural network

Design of experiment and artificial neural networks (ANN) have been effectively employed to predict the rate of uptake of Zn(II) ions onto defatted pongamia oil cake. Four independent variables such as, pH (2.0-7.0), initial concentration of Zn(II) ions (50-500 mg/L), temperature (30ºC-50 °C), and dosage of biosorbent (1.0-5.0 g/L) were used for the batch mode while the three independent variables viz. flowrate, initial concentration of Zn(II) ions and bed height were employed for the continuous mode. Second-order polynomial equations were then derived to predict the Zn(II) ion uptake rate. The optimum conditions for batch studies was found to be pH: 4.45, metal ion concentration: 462.48 mg/L, dosage: 2.88 g/L, temperature: 303 K and on the other hand the column studies flow rate: 5.59 mL/min, metal ion concentration: 499.3 mg/L and bed height: 14.82 cm. Under these optimal condition, the adsorption capacity was 80.66 mg/g and 66.29 mg/g for batch and column studies, respectively. The same data was fed to train a feed-forward multilayered perceptron, using MATLAB to develop the ANN based model. The predictive capabilities of the two methodologies were compared, by means of the absolute average deviation (AAD) (4.57%), model predictive error (MPE) (4.15%), root mean square error (RMSE) (3.19), standard error of prediction (SEP) (4.23) and correlation coefficient (R) (0.99) for ANN and for RSM AAD (16.27%), MPE (21,25%), RMSE (13.15%), SEP and R (0.96) by validation data. The findings suggested that compared to the prediction ability of RSM model, the properly trained ANN model has better prediction ability. In batch studies, equilibrium data was used to determine the isotherm constants and first and second order rate constants. In column, bed depth service time (BDST) and Thomas model was used to fit the obtained column data.

Study on Adsorption of Cu and Ba from Aqueous Solutions Using Nanoparticles of Origanum (OR) and Lavandula (LV)

Wild herbs (Origanum (OR) and Lavandula (LV)) were used as environment-friendly adsorbents in this study. The adsorbents were used for adsorption of Cu and Ba from water. The adsorption of heavy metals onto OR and LV was dependent on particle size, dose, and solution pH. The diameter of adsorbent particles was less than 282.8 nm. The adsorption follows second-order kinetics. Langmuir and Freundlich models have been applied to describe the equilibrium data, and the thermodynamic parameters, the Gibbs free energy, ∆G°, enthalpy, ∆H°, and entropy, ∆S°, have been determined. The positive value of ∆H° suggests that the adsorption of heavy metals by the wild herbs is endothermic. The negative values of ∆G° at all the studied temperatures indicate that the adsorption is a spontaneous process. It can be concluded that OR and LV are promising adsorbents for the removal of heavy metals from aqueous solutions over a range of concentrations.

Brown marine macroalgae as natural cation exchangers for toxic metal removal from industrial wastewaters: A review

The discharge of inadequately treated or untreated industrial wastewaters has greatly contributed to the release of contaminants into the environment, including toxic metals. Toxic metals are persistent and bioaccumulative, being their removal from wastewaters prior to release into water bodies of great concern. Literature reports the use of brown marine macroalgae for toxic metals removal from aqueous solutions as an economic and eco-friendly technique, even when applied to diluted solutions. Minor attention has been given to the application of this technique in the treatment of real wastewaters, which present a complex composition that can compromise the biosorption performance. Therefore, the main goal of this comprehensive review is to critically outline studies that: (i) applied brown marine macroalgae as natural cation exchanger for toxic metals removal from real and complex matrices; (ii) optimised the biosorption process in a fixed-bed column, which was further scaled-up to pilot plants. An overview of toxic metals sources, chemistry and toxicity, which are relevant aspects to understand and develop treatment techniques, is initially presented. The problem of water resources pollution by toxic metals and more specifically the participation of metal finishing industries in the environmental contamination are issues also covered. The current and potential decontamination methods are presented including a discussion of their advantages and drawbacks. The literature on biosorption was reviewed in detail, considering especially the ion exchange properties of cell wall constituents, such as alginate and fucoidan, and their role in metal sequestration. Besides that, a detailed description of biosorption process design, especially in continuous mode, and the application of mechanistic models is addressed.

Biosorption of Zn(II) from industrial effluents using sugar beet pulp and F. vesiculosus: From laboratory tests to a pilot approach

The aim of this work was to demonstrate the feasibility of the application of biosorption in the treatment of metal polluted wastewaters through the development of several pilot plants to be implemented by the industry. The use as biosorbents of both the brown seaweed Fucus vesiculosus and a sugar beet pulp was investigated to remove heavy metal ions from a wastewater generated in an electroplating industry: Industrial Goñabe (Valladolid, Spain). Batch experiments were performed to study the effects of pH, contact time and initial metal concentration on metal biosorption. It was observed that the adsorption capacity of the biosorbents strongly depended on the pH, increasing as the pH rises from 2 to 5. The adsorption kinetic was studied using three models: pseudo first order, pseudo second order and Elovich models. The experimental data were fitted to Langmuir and Freundlich isotherm models and the brown alga F. vesiculosus showed higher metal uptake than the sugar beet pulp. The biomasses were also used for zinc removal in fixed-bed columns. The performance of the system was evaluated in different experimental conditions. The mixture of the two biomasses, the use of serial columns and the inverse flow can be interesting attempts to improve the biosorption process for large-scale applications.

Interpretation of single and competitive adsorption of cadmium and zinc on activated carbon using monolayer and exclusive extended monolayer models

In this work, a modeling analysis based on experimental tests of cadmium/zinc adsorption, in both single-compound and binary systems, was carried out. All the experimental tests were conducted at constant pH (around neutrality) and temperature (20 °C). The experimental results showed that the zinc adsorption capacity was higher than that of cadmium and it does not depend on cadmium presence in binary system. Conversely, cadmium adsorption is affected by zinc presence. In order to provide good understanding of the adsorption process, two statistical physics models were proposed. A monolayer and exclusive extended monolayer models were applied to interpret the single-compound and binary adsorption isotherms of zinc and cadmium on activated carbon. Based on these models, the modeling analysis demonstrated that zinc is dominant in solution and more favorably adsorbed on activated carbon surface. For instance, in single-compound systems, the number of ions bound per each receptor site was n (Zn²⁺) = 2.12 > n (Cd²⁺) = 0.98. Thus, the receptor sites of activated carbon are more selective for Zn²⁺ than for Cd²⁺. Moreover, the determination of adsorption energy through the adopted models confirmed that zinc is more favored for adsorption in single-compound system (adsorption energies equal to 12.12 and 7.12 kJ/mol for Zn and Cd, respectively) and its adsorption energy does not depend on the cadmium presence in binary system. Finally, the adsorption energy values suggested that single-compound and binary adsorption of zinc and cadmium is a physisorption.

Biosorption of neodymium on Chlorella vulgaris in aqueous solution obtained from hard disk drive magnets

In recent years, biosorption is being considered as an environmental friendly technology for the recovery of rare earth metals (REE). This study investigates the optimal conditions for the biosorption of neodymium (Nd) from an aqueous solution derived from hard drive disk magnets using green microalgae (Chlorella vulgaris). The parameters considered include solution pH, temperature and biosorbent dosage. Best-fit equilibrium as well as kinetic biosorption models were also developed. At the optimal pH of 5, the maximum experimental Nd uptakes at 21, 35 and 50°C and an initial Nd concentration of 250 mg/L were 126.13, 157.40 and 77.10 mg/g, respectively. Analysis of the optimal equilibrium sorption data showed that the data fitted well (R2 = 0.98) to the Langmuir isotherm model, with maximum monolayer coverage capacity (qmax) of 188.68 mg/g, and Langmuir isotherm constant (KL) of 0.029 L/mg. The corresponding separation factor (RL) is 0.12 indicating that the equilibrium sorption was favorable. The sorption kinetics of Nd ion follows well a pseudo-second order model (R2>0.99), even at low initial concentrations. These results show that Chlorella vulgaris has greater biosorption affinity for Nd than activated carbon and other algae types such as: A. Gracilis, Sargassum sp. and A. Densus.

Cow bones char as a green sorbent for fluorides removal from aqueous solutions: batch and fixed-bed studies

Cow bone char was investigated as sorbent for the defluoridation of aqueous solutions. The cow bone char was characterized in terms of its morphology, chemical composition, and functional groups present on the bone char surface using different analytical techniques: SEM, EDS, N₂-BET method, and FTIR. Batch equilibrium studies were performed for the bone chars prepared using different procedures. The highest sorption capacities for fluoride were obtained for the acid washed (q = 6.2 ± 0.5 mg/g) and Al-doped (q = 6.4 ± 0.3 mg/g) bone chars. Langmuir and Freundlich models fitted well the equilibrium sorption data. Fluoride removal rate in batch system is fast in the first 5 h, decreasing after this time until achieving equilibrium due to pore diffusion. The presence of carbonate and bicarbonate ions in the aqueous solution contributes to a decrease of the fluoride sorption capacity of the bone char by 79 and 31 %, respectively. Regeneration of the F-loaded bone char using 0.5 M NaOH solution leads to a sorption capacity for fluoride of 3.1 mg/g in the second loading cycle. Fluoride breakthrough curve obtained in a fixed-bed column presents an asymmetrical S-shaped form, with a slow approach of C/C ₀ → 1.0 due to pore diffusion phenomena. Considering the guideline value for drinking water of 1.5 mg F^-/L, as recommended by World Health Organization, the service cycle for fluoride removal was of 71.0 h ([F^-]_feed ∼ 9 mg/L; flow rate = 1 mL/min; m _sorbent = 12.6 g). A mass transfer model considering the pore diffusion was able to satisfactorily describe the experimental data obtained in batch and continuous systems.

Heavy Metal Adsorption onto Kappaphycus sp. from Aqueous Solutions: The Use of Error Functions for Validation of Isotherm and Kinetics Models

Biosorption process is a promising technology for the removal of heavy metals from industrial wastes and effluents using low-cost and effective biosorbents. In the present study, adsorption of Pb²⁺, Cu²⁺, Fe²⁺, and Zn²⁺ onto dried biomass of red seaweed Kappaphycus sp. was investigated as a function of pH, contact time, initial metal ion concentration, and temperature. The experimental data were evaluated by four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models). The adsorption process was feasible, spontaneous, and endothermic in nature. Functional groups in the biomass involved in metal adsorption process were revealed as carboxylic and sulfonic acids and sulfonate by Fourier transform infrared analysis. A total of nine error functions were applied to validate the models. We strongly suggest the analysis of error functions for validating adsorption isotherm and kinetic models using linear methods. The present work shows that the red seaweed Kappaphycus sp. can be used as a potentially low-cost biosorbent for the removal of heavy metal ions from aqueous solutions. Further study is warranted to evaluate its feasibility for the removal of heavy metals from the real environment.