Aqueous Waste Research Articles

Molecular Insights of Separation of Lanthanide Metals from Aqueous Waste by Using Directional Solvent Extraction

Molecular Insights of Separation of Lanthanide Metals from Aqueous Waste by Using Directional Solvent Extraction

Comparative study of Ni nanoparticles synthetized using electroless Ni plating waste and an analytical Ni reagent. Characterization and possible application in magnetic fluids

Wastewater from the electroless industry represents a potential danger to the environment and health, mainly due to its heavy metal content. In this study, nickel nanoparticles were synthesized through chemical reduction precipitation by using an electroless nickel plating waste and hydrazine sulfate as reducing agent. The aim of the present work is twofold. First we want to extract the metal from the aqueous medium, minimizing its content to levels allowed by environmental regulations. Second, we aim to valorize the residue by recovering the precipitated nickel to be applied as a solid phase in a magnetic fluid (MF). It is found that the present synthesis method using N2H4 as reducing agent, allowed us to minimize the Ni concentration in the aqueous waste in 97.49 %. The properties of the recovered Ni precipitate is compared with the Ni nanoparticles (NPs) obtained from a solution prepared with analytical grade nickel sulfate. The synthesized materials from both the waste (Ni-R) and analytical reagent (Ni-A) were characterized by comparing their chemical, physical, and morphological properties. In both cases, the Ni-R and Ni-A precipitates, spherical Ni NPs of 8–10 nm crystallite sizes are obtained, agglomerated in a bimodal size distribution centered at 174.6 and 383.4 nm, and a monomodal size distribution centered at 63.6 nm, respectively. Both Ni precipitated samples are ferromagnetic, but the Ni-R sample has a higher magnetic saturation of 40 emu/g compared to 8 emu/g of the Ni-A sample. The difference in the rheological behavior of both precipitates could be attributed to the presence of surface oxidation having a relatively less contribution in the case of the Ni-R particles due to the higher average size of the particles. The Fe content, probably coming from the nickel-plated parts in spent baths, is slightly higher in the Ni-R sample. Thus, the present work shows that it is possible to valorize an industrial Ni-based residue, by obtaining Ni precipitates that in magnetic fluids give even better results than those expected under more rigorous experimental conditions, i.e., in cases where the quality of the chemical precursors is usually a determining factor.

Reinventing primary reactive oxygen species evolved from H2O2 heterolysis on FeOCl via SiO2 encapsulation

Feδ+/3+ defects on FeOCl surface interact with H2O2 to produce diverse reactive oxygen species (ROS) including •OH, •OOH, O2•-, Fe4+=O, and 1O2, whose relative contributions to aqueous pollutant degradation have been debatable and only partially clarified. Herein, SiO2 with O2- acting as an electron donor served to encapsulate FeOCl to form FeOCl-SiO2, whose interface bore Feδ+/3+ distinct from those of FeOCl surface under H2O2-containing aqueous phases in terms of composition and electron affinity. The FeOCl-SiO2 interface bore plentiful Feδ+ and minute Fe3+, from which Fe4+=O was generated yet remained barely accessible to bulky contaminants. Conversely, the FeOCl surface afforded plentiful Fe3+ and a non-negligible amount of Feδ+, from which copious O2•- and a moderate amount of Fe4+=O were produced, respectively, with high accessibility to bulky pollutants. Albeit with the production of •OH on FeOCl and FeOCl-SiO2, plots of their initial contaminant decomposition rates versus contaminant ionization potentials subjected to the correction for contaminant adsorption or Feδ+/3+ leaching along with scavenging/recycle runs corroborated that Fe4+=O and/or 1O2 function as the major ROS in fragmenting aqueous wastes upon exposure of the FeOCl-containing catalysts to H2O2-rich conditions. This was unanticipated when considering that the lifetimes and redox potentials of Fe4+=O and 1O2 are smaller than the corresponding values of •OH and that the evolution of •OH, Fe4+=O, and 1O2 on FeOCl was energetically favorable, as demonstrated by density functional theory calculations.

Supercritical hydrothermal combustion and enhanced degradation characteristics of phenol

Supercritical hydrothermal combustion is a green combustion technology that produces flames in supercritical water (SCW), which can realize efficient disposal of aqueous wastes. In this study, the typical pollutant phenol is investigated through tubular reactor experiments and mechanism analysis to explore its hydrothermal combustion properties and enhanced degradation effects on refractory species. The results show that 3.06 and 3.41 wt% phenol can be self-ignited in the tubular reactor with a critical preheating temperature of 460 °C. Methanol could improve the ignition and burnout characteristics of phenol. As the COD ratio of methanol was greater than 0.35, the ignition temperature of phenol was reduced to 420 °C, with TOC removal rate achieving 99.9%. At 460 °C, phenol positively influenced the heat release during combustion of phenol/methanol. In oxidation of phenol/ammonia, 1.61 wt% phenol resulted in the reaction temperature rising by around 62.0 °C, allowing a NH4-N removal rate of 92.8% through its synergistic kinetic and thermal effects. Whereas, the nitrogen-containing intermediates from ammonia inhibited phenol oxidation. Finally, a mechanism-based kinetics model for oxidation of phenol in SCW was developed by means of real gas properties and sensitive reaction step modifications, which was viable for simulating the ring-opening path of phenol.

Effect of operating variables on selective radiostrontium separation from aqueous waste matrices using a novel crown ether-based amino-modified mesoporous silica sorbent

A new sorbent, DFDB18C6@SBA-NH2, created by grafting diformal dibenzo-18-crown-6-ether (DFDB18C6) onto amino-modified mesoporous silica (SBA-NH2) has been used for the selective removal of radiostrontium (r-Sr: 90Sr) from aqueous waste. The Sr-sorption behavior was investigated at various operating conditions, including pH, contact time, initial Sr2+ concentration, temperature, and the presence of competing ions (e.g., Li, Na, K, Rb, Ca, Mg, and Ba). Kinetic investigations showed that the sorption process followed pseudo-second order kinetics, whereas isotherm modeling demonstrated that the Langmuir model provided the most excellent fit, implying monolayer sorption. The thermodynamic study indicated that the sorption process is endothermic. The sorbent effectively removed 90Sr (∼99.67 %) from Chornobyl-derived radioactive wastewater in the presence of other ions. These findings suggest the potential of DFDB18C6@SBA-NH2 as an effective tool for 90Sr separation from aqueous waste matrices.

Supported liquid membrane with selective stripping for separative recovery of copper and zinc from plating wastewater

For separation and recovery of different but chemically similar metal from dilute wastewater with reduced process complexity and cost, a supported liquid membrane (SLM) system that utilizes a single carrier together with strip dispersion for selective stripping of coextracted metal ions was proposed to enable concurrent separation and recovery. This study aims to investigate the effectiveness of the proposed SLM system for separative recovery of copper and zinc from real plating wastewater. Solvent extraction experiments were conducted to understand the effect of feed pH and carrier concentration on organic phase migration to the aqueous phase. The effect of stirring speed on the SLM transport rate was studied using synthetic feed. Combined with the insights from our previous study, appropriate settings were identified and applied to the SLM system. The SLM system could recover 83.7% copper with 91.0% purity and 85.5% Zn with 99.3% purity from the plating wastewater in 30 h. The findings indicate the feasibility of using SLM with selective stripping for the concurrent separation and recovery of copper and zinc from a dilute aqueous waste stream predominantly containing these two metals.

Evaluation of low-cost adsorbent of Manilkara zapota for phenol removal in aqueous solution

Industrial waste water is aqueous waste that results from the dissolution or suspension of materials in water. Phenol is the substances that are utilized in the industry. The main aim of the study is to treat the wastewater for the removal of phenol by batch mode adsorption using the agricultural waste that is Manilkara zapota. The characterization of the adsorbent was determined by FTIR, SEM and XRD. The adsorption process is to evaluate the kinetics of adsorption and the pseudo second order kinetics showed good regression value of 0.995 for 60 mg/L. The Langmuir capacity was found to be 9.8 mg/g. The optimum time to reach equilibrium of adsorption is 2 hours. From the findings the Manilkara zapota prove to be a promising adsorbent for the removal of phenol from the aqueous environment.

Ammonia recovery via stripping from hydrothermal liquefaction aqueous from sludge for anaerobic co-digestion pretreatment

Hydrothermal liquefaction (HTL) is a thermo-chemical method of processing wastewater solids that could be preferential over anaerobic digestion (AD) because it produces a greatly reduced volume of solids. Instead, the effluent can be separated into biocrude refined into fuel, hydrochar a carbon-rich solid and HTL aqueous waste. Unfortunately, HTL aqueous is high in ammonia, phenolics, and nitrogen heterocyclic compounds that can inhibit AD if used for treatment. Ammonia stripping was tested for pretreatment of HTL aqueous from dewatered mixed sludge at 350 °C, 15 min and recovering ammonia. Seven stripping reactor conditions were run, and the best results were seen at 85 °C, a pH of 9.3 and 500 mL/min air flow rate. This case achieved ammonia and total phenolic compounds removal of 79.5 ± 0.1 and 32 ± 1 %, respectively, in 4 h. The ammonia stripping was coupled with acid adsorption to produce an ammonium sulphate salt with fertilizer value. The ideal ammonia stripping conditions produced a salt with a purity of 98.0 ± 0.05 % and represented an ammonia recovery of 73.9 ± 0.04 %. Semi-continuous flow bench-scale thermophilic anaerobic co-digestion of HTL aqueous with municipal sludge found that 12 % of influent chemical oxygen demand (COD) can come from HTL aqueous without inhibition if pretreated with ammonia stripping, while the digester fed with a similar COD from non-pretreated HTL aqueous showed inhibition. Under mesophilic conditions, semi-continuous flow anaerobic co-digestion was successful for non-pretreated and pretreated HTL aqueous even with 24 % and 22 % of influent COD provided by HTL aqueous, respectively.

A Polymer‐Functionalized GO Composite Prepared through Pickering Emulsion Polymerization for Selective Removal of Zr from Acidic Solutions

AbstractFor the selective removal of Zr from PUREX originated acidic aqueous waste of metallic fuel, an adsorbent based on graphene oxide (GO)‐polystyrene composite functionalized with amide functional group was developed. Improved Hummers’ oxidation of graphite powder was utilized to produce GO and the amide moiety was linked to GO via chemical functionalization. The amide modified GO was converted to GO‐polystyrene composite microspheres through pickering emulsion assisted route. FT‐IR, XRD and SEM analyses were employed to characterize the composite adsorbent. The adsorption behavior of Zr was examined under varying experimental conditions. Adsorption was modeled using several adsorption and kinetic models. The Zr adsorption capacity calculated based on the Langmuir adsorption isotherm and Pseudo‐first‐order models exhibited a close agreement. Adsorption studies using simulated U‐Pu‐Zr originated PUREX aqueous waste signifies the superior Zr‐adsorption capacity (~50 mg g−1), even in the presence of other possible interfering elements present in SHLLW.

Theoretical investigations of the potential application of PVA-mixed-valent tunnel structured manganese oxide nano-composite in continuous simultaneous removal of multi-contaminants from aqueous waste stream

The potential use of PVA-mixed-valent tunnel structured manganese oxide nano-composite in the removal of multi-contaminants form aqueous solutions was assessed by studying the continuous simultaneous removal of lead, caesium, and cobalt. Within this context, the morphology and the nature of nanoparticle inclusion into the PVA matrix was assessed using SEM–EDX analysis. The nanoparticles are homogenously distributed in the polymeric matrix with some agglomerated inclusions of these particles. The thermal and chemical stability analyses prove the stability of the material up to 180 °C and in slightly acidic to slightly alkaline solutions. The analysis of the gravimetric thermal data shows that the thermal treatment is a feasible end of life management route for this material. The values of percentage uptake and bed capacity indicate the feasibility of the use of this material in the simultaneous removal of lead, caesium and cobalt. The breakthrough curves analyses provide insights into the breakthrough characteristics and underlying removal mechanisms. It was found that the removal reaction follows Langmuir kinetics of adsorption–desorption and that the rate driving forces follow second order reversible reaction kinetics, where the sorption occur at energetically equal sites.

“PAW” a smart analytical process assessing lipophilicity of solutes in mixtures

BackgroundThe analysis of mixtures of contaminants remains a challenging task in many fields, including water quality and waste management. For example, the degradation of industrial waste such as plastics, leads to complex mixtures with hundreds of organic contaminants and often non-referenced analytes. In such cases, non-targeted or effects-based analyses provide complementary information to classical targeted-analyses, regarding contaminants nature or properties (molecular mass, lability, toxicity). In this study, a novel analytical method is proposed to characterise mixtures of unknown organic contaminants, with a focus on the lipophilicity of solutes. ResultsThe proposed process, named “PAW“ (Partition of Aqueous Waste), aims at the quantification of octanol-water partition coefficients (POW) of mixed organic analytes. The process is based on sequential liquid-liquid partition equilibria. The output result is a lipophilicity histogram of the solutes, screened according to the chosen detection method. The process quantifies the distribution of analytes as a function of their octanol-water partition coefficients, without requiring any identification or prior knowledge. The PAW process is applicable with various detectors (UV–Visible, total carbon, liquid scintillation, etc.) allowing to focus on specific families of contaminants (e.g. organic solutes, colloids, 14C-bearing, etc.). Experimental proofs of concept are proposed, illustrating process implementation and possible fields of application. The first example deals with purity analysis of synthetic radiolabeled compounds. The second example aims the monitoring of cellulose degradation and quantification of the lipophilicity of degradation products. SignificanceThe PAW analytical process seems especially useful for characterisation of mixtures containing both hydrophilic and lipophilic compounds, e.g. neutral and ionizable organic contaminants, hardly characterisable simultaneously by chromatographic methods. It could be complementary to more detailed targeted or screening analysis of samples and effluents. For example it may help assessing the composition and environmental fate of mixtures of unknown analytes, thus facilitating waste management or mitigation strategies.

Radiation grafted polyacrylic acid–polyurethane foam copolymer for efficient toxic metal removal from aqueous waste: a sustainable approach to waste management

The acrylic acid-grafted functionalized base polyurethane foam (PAA-g-PUf) is synthesized through mutual radiation grafting technique using acrylic acid as functional monomers and polyurethane form (PUf) with macroporous structure as base polymer, for the extraction of lead from the aqoueous waste streams. The incorporation of functionality on PUf is identified and confirmed by FT-IR spectroscopy, degree of grafting and thermal stability by TGA–DSC technique while the surface morphology, and pores dimensions are evaluated by SEM techniques. The kinetics measurements indicate that the synthesized sorbent reaches its saturation sorption capacity within 10 min at ~ 25 °C under near-neutral pH condition. The monolayer sorption capacity of the synthesized PAA-g-PUf for lead ion (Pb2+) is calculated from Langmuir’s model and found to be ~ 257 mg g−1, which is quite good as compared to the other functionalized material available. These grafted foams are quite efficient over a wide range of concentrations and temperature of the experimental solutions. In this study, the adsorbed lead ions are eluted out in 0.5 M HCl strippent efficiently. These sorbents exhibit excellent reusability up to five cycles without losing appreciable capacity, suggesting better usability in real water samples for many cycles. The polyurethane foam used was obtained from municipal waste, and hence, they cannot generate any additional secondary waste to the environment and make the process more sustainable and economically viable.Graphical abstract

Degradation of diethyl phthalate by photolysis of hydrogen peroxide electrogenerated using a Printex L6 carbon modified with Benzophenone cathode in an improved tangential flow cell

In this work, a gas diffusion electrode (GDE) made of Printex L6 carbon modified with 2.0% w/w of benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (PL6C/BTDA 2%) was employed as cathode in a new 3D printed electrochemical cell with tangential flow. With this configuration, the performance of the technology was evaluated for hydrogen peroxide (H2O2) electrogeneration and remediation of aqueous wastes contaminated with diethyl phthalate (DEP) using different H2O2-based advanced oxidation processes (AOPs). The electrogeneration study was carried out varying the current density applied to the system, and it was found that 50 mA cm-2 was the best performing value, resulting in remarkable Faradaic efficiencies of nearly 100%. This led to the production of higher amounts of H2O2 (442.5 mg L-1) in 90 minutes at an acceptable energy consumption (8.5 kWh kg-1) compared to values reported in the literature. Based on these findings, H2O2-based AOPs were employed to investigate the removal of DEP in cathodic compartment, including mediated electrochemical degradation with electrogenerated H2O2 (e-H2O2) and the integration of this technology with ultraviolet-C (UVC) photolysis (e-H2O2/UVC). The integrated e-H2O2/UVC obtained the best performance compared to single photolysis and e-H2O2, leading to the total elimination of DEP (90 μmol L-1) within only 30 min of treatment, reaching the highest kinetic rate constant (0.3 min-1). Fifteen by-products, generated through oxidation processes studied, were successfully identified by LC-MS/MS, enabling the proposal of the degradation mechanism of DEP.

Hydrometallurgical Method of Producing Lithium Perrhenate from Solutions Obtained during the Processing of Li-Ion Battery Scrap

The work presents the research results regarding the development of an innovative technology for the production of lithium perrhenate. The new technology is based entirely on hydrometallurgical processes. The source of lithium was solutions created during the processing of Li-ion battery masses, and the source of rhenium was perrhenic acid, produced from the scraps of Ni-based superalloys. The research showed that with the use of lithium carbonate, obtained from post-leaching solutions of Li-ion battery waste and properly purified (by washing with water, alcohol, and cyclic purification with CO2), and perrhenic acid, lithium perrhenate can be obtained. The following conditions: room temperature, time 1 h, 30% excess of lithium carbonate, and rhenium concentration in the acid from 20 g/dm3 to 300 g/dm3, allowed to produce a compound containing a total of 1000 ppm of metal impurities. The developed technology is characterized by the management of all aqueous waste solutions and solid waste and the lack of loss of valuable metals such as rhenium and lithium after the initial precipitation step of lithium carbonate.

Highly efficient hydrophobic nanocomposite in the decontamination of micropollutants and bacteria from aqueous wastes: A sustainable approach

Micro-pollutants (specifically antibiotics and personal care products) and potential bacterial contamination pose a severe threat to human health and marine life. The study derives indigenous novel fibrous hydrophobic nanocomposite, efficient in decontaminating the micro-pollutants (tetracycline (TC) and bisphenol A (BPA)) and potential pathogens (S. pyogenes and E. coli) from aqueous wastes. A facile method synthesizes the fibrous attapulgite (ATP)- poly(4-vinylpyridine-co-styrene) (PVP) framework decorated in situ with the Ag0 nanoparticles (ATP@PVP/Ag0). A greener method using the Artocarpus heterophyllus leaf extract derives the Ag0(NPs). Various analytical methods extensively characterize the materials. A comprehensive study that includes pH, concentration, background electrolytes, and ionic strength reveals the sorptive removal insights of TC and BPA utilizing the ATP@PVP solid. The elimination of tetracycline (TC) and bisphenol A (BPA) agrees well with the pseudo-second-order kinetics. The pH 3.07 and 6.06 favor removing TC and BPA with the capacity of 10.86 mg/g and 17.36 mg/g at 25 °C. The hydrogen bonding and hydrophobic interactions predominate the sorption mechanism, and the material shows remarkable stability and reusability in repeated sorption/desorption operations. Similarly, the natural water implications and flow-bed system show fair applicability of solid in decontaminating the TC and BPA in an aqueous medium. Further, the material ATP@PVP/Ag0 exhibits very high inhibition of potential pathogens S. pyogenes and E. coli and optimizes the solid dose and solution pH.

Glass formulation and lab-scale testing of glasses designed for in-can Melter and in-container Vitrification of high-assay low-enriched uranium aqueous polishing Raffinate waste

Glasses were designed for processing a nuclear waste from aqueous polishing of high-assay low-enriched uranium using either In-Can Melter or GeoMelt® In-Container Vitrification™ (ICV) technologies, which operate at temperatures of Tp ≤ 1100 °C and Tp ≤ 1450 °C, respectively. Due to the different operating conditions, the melt and glass properties were optimized differently for each technology. Each glass was designed to optimize for maximum waste loading while simultaneously satisfying processing (e.g., crystallization, viscosity, conductivity) and product quality (e.g., durability, hazard characteristic, crystal content) constraints. The raffinate waste contains high nitric acid (4 M) and low total solids (9 g∙L−1) concentrations. Feed preparation processes were tested to facilitate concentration and nitrate destruction/removal while controlling redox of the melter feed. A successful lab-scale feed process including sugar addition and spray-drying was performed to generate an adequate melter feed for ICV processing.

Naphthenic acids removal using N-doped hemp fibers based mesoporous carbon from aqueous waste stream

There is a substantial need for removing the contaminants from aqueous waste stream using affordable, stable, and active adsorbents, such as heteroatom-doped carbonaceous materials. Heteroatom such as N-doped carbonaceous materials greatly improve the performance of carbon materials by enhancing their conductivity, basicity, oxidation stability, catalytic activity and adsorption capacity. In this study, hemp fibers (HFs) and N-aminoguanidine were utilized as carbon and nitrogen precursors to synthesize N-functionalized mesoporous carbon materials (N-HFCs) via simultaneous activation and carbonization with ZnCl2. Higher BET surface area with a distinctive mesoporous structure and the covalent bond between N and C was developed in the prepared carbon, making N-HFCs suitable for adsorbing naphthenic acids (2-naphthoic acid and benzoic acid) from aqueous waste streams. Developed covalent bond helps to prevent the leaching of carbonaceous materials during adsorption study. The results showed that N-HFC-2 (ZnCl2: N-HFs ratio = 2:1) exhibited a higher removal efficiency of naphthenic acids (2-naphthoic acid and benzoic acid) compared to nonfunctionalized porous carbon (HFC). Adsorption of 2-naphthoic acid and benzoic acid on the adsorbents followed the typical monolayer type of Langmuir adsorption model. The maximum adsorption capacity of HFC after 48 h was evaluated as 70 and 27 mg/g for 2-naphthoic acid and benzoic acid. Likewise, the maximum adsorption capacity of N-HFC-2 for 2-naphthoic acid and benzoic acid was found to be 71 and 33 mg/g. In the adsorption kinetic experiment, adsorption of 2-naphthoic acid and benzoic acid reached equilibrium within 1 h using both the adsorbents (N-HFC-2 and HFC). Adsorption kinetics were analyzed using pseudo-first-order and pseudo-second-order kinetic models and were found to follow a pseudo-second-order kinetic model. Although changing pH from 4.4 to 8.5 did not have any significant effect on the removal efficiency of 2-napthoic acid using HFC and N-HFC-2, the removal efficiency of benzoic acid was decreased from 94 to 60 % using HFC and increased from 98 to 100 % using N-HFC-2. Comparative evaluations demonstrated that the mesoporous carbonaceous materials derived from HFs are an attractive adsorbent for removal of such contaminants from contaminated aqueous streams.

Rapid wet grinding carbonation of sintering red mud for highly efficient CO2 sequestration and Cr solidification

Sintering red mud (SRM) is an alkaline and aqueous solid waste from bauxite sintering for alumina production. The challenges in the effective utilization of SRM are strong alkalinity, aqueous state and leaching toxicity of the heavy metals. Herein, a rapid wet grinding carbonation technique of simultaneous injection of CO2 in wet grinding process was proposed. The rapid carbonation of alkaline metal ions and the efficient solidification of heavy metal ions were achieved in the wet grinding carbonation. After 40 min of short-term carbonation, the CO2 uptake and carbonation degree of SRM reached 30.25 g CO2/100 g SRM and 79.31% respectively. The high-efficiency CO2 uptake of SRM was attributed to the continuous stripping of the attached surface CaCO3 layer by wet grinding, the constantly exposed new surface area after refinement and the largely increased Ca2+ concentration, which was 12.5 times the initial value at 10 min. Furthermore, the simultaneous carbonation realized the solidification of dissolved chromium ion (Cr(III)/Cr(VI)), which was transformed into CaCrO4, Ca3Cr2(OH)12 or Cr(OH)n(CO3)n(3n-3)- complexes under the weak acid environment of CO2. After 40 min of wet grinding carbonation, the Cr concentration was notably decreased by 85.71 %, which was lower than the limit of groundwater standard requirement.

Synthesis and characterization of nanostructured mesoporous alumina embedded PES beads for uranium extraction from aqueous radioactive waste

Synthesis and characterization of nanostructured mesoporous alumina embedded PES beads for uranium extraction from aqueous radioactive waste

Roles of pH and phosphate in rare earth element biosorption with living acidophilic microalgae

The increasing demand for rare earth elements (REEs) has spurred interest in the development of recovery methods from aqueous waste streams. Acidophilic microalgae have gained attention for REE biosorption as they can withstand high concentrations of transition metals and do not require added organic carbon to grow, potentially allowing simultaneous sorption and self-replication of the sorbent. Here, we assessed the potential of Galdieria sulphuraria for REE biosorption under acidic, nutrient-replete conditions from solutions containing ≤ 15 ppm REEs. Sorption at pH 1.5–2.5 (the growth optimum of G. sulphuraria) was poor but improved up to 24-fold at pH 5.0 in phosphate-free conditions. Metabolic activity had a negative impact on REE sorption, additionally challenging the feasibility of REE biosorption under ideal growth conditions for acidophiles. We further examined the possibility of REE biosorption in the presence of phosphate for biomass growth at elevated pH (pH ≥ 2.5) by assessing aqueous La concentrations in various culture media. Three days after adding La into the media, dissolved La concentrations were up to three orders of magnitude higher than solubility predictions due to supersaturation, though LaPO4 precipitation occurred under all conditions when seed was added. We concluded that biosorption should occur separately from biomass growth to avoid REE phosphate precipitation. Furthermore, we demonstrated the importance of proper control experiments in biosorption studies to assess potential interactions between REEs and matrix ions such as phosphates.Key points• REE biosorption with G. sulphuraria increases significantly when raising pH to 5• Phosphate for biosorbent growth has to be supplied separately from biosorption• Biosorption studies have to assess potential matrix effects on REE behavior