Adsorption of vanadium (V) ions from the aqueous solutions on different biomass-derived biochars

Removal of vanadium(V) ions from acidic water using reusable manganese oxide sorbents

Manganese oxide (MnOx) was studied for its ability to adsorb vanadium (V) ions for applications in acidic water treatment. Three MnOx types: naturally-occurring (NatMnO), commercially-derived (ComMnO), and laboratory synthesised (SynMnO) were examined in batch systems under varying pH, adsorbent dosage, ionic strength, and contact time. The greatest V sorption occurred at acidic pH, following the order: NatMnO > SynMnO > ComMnO, with maximum adsorption capacities of 54.0, 26.0, and 10.4 mg/g, respectively (at pH 3.0, mass/volume ratio of 2 g/L, concentration of 100 mg/L, 24 hours). Adsorption equilibrium data best fit the Freundlich isotherm, indicating multilayer adsorption, while kinetic data followed a two-constant rate model, suggesting both physical and chemical sorption. Solution pH was found to have a significant impact, with V removal by MnOx most effective at low pH, likely due to the negative zeta potential of the MnOx under such conditions. MnOx reusability was investigated using repeated sorption and desorption experiments with 0.1 M HCl, 0.1 M NaOH, and deionised water to regenerate the MnOx. The regenerated MnOx exhibited similar or enhanced ability to sorb V ions from solution. Overall, these results confirm the unique ability of MnOx as a reusable sorbent for V removal from acidic water, while also enhancing our mechanistic understanding of the removal process. This finding supports the development of sustainable solutions for acidic water treatment, contributing to efforts to address this critical environmental challenge.

Remediation of vanadium(V)-contaminated groundwater by the Shewanella oneidensis MR-1, Fe2O3, and biochar composite

Vanadium, essential for steel production and energy storage, is increasingly found in groundwater due to extensive mining and industrial activities. Its high mobility and reactivity pose significant environmental risks. This study developed an Shewanella oneidensis MR-1- Fe2O3-biochar composite to enhance vanadium bioremediation. The composite exhibited strong vanadium resistance, achieving 92.5 ± 1.48% removal of pentavalent vanadium [V(V)] at 100 mg/l with an optimal biochar/Fe₂O₃ ratio of 10:1. Its efficiency was further assessed under varying pH, organic carbon levels, and V(V) concentrations. XPS analysis confirmed the presence of tetravalent vanadium [V (IV)] and divalent iron [Fe (II)], while FTIR spectroscopy identified functional groups (-OH, C=C, C=O) within the composite. These results suggest a synergistic removal mechanism involving complexation, dissimilatory iron reduction, and microbial V(V) reduction. This study provides a promising strategy for remediating V(V)-contaminated groundwater. PRACTITIONER POINTS: A novel composite consisted of Shewanella oneidensis MR-1, Fe2O3, and biochar was synthesized Complex promoted microbial life and increased resistance towards V(V) Complexation, Fe (II) oxidation, and bioreduction collectively contributed to V(V) removal.

New fruit waste-derived activated carbons of high adsorption performance towards metal, metalloid, and polymer species in multicomponent systems

The main aim of the study was to develop new fruit waste-derived activated carbons of high adsorption performance towards metals, metalloids, and polymers by the use of carbon dioxide (CO2)-consuming, microwave-assisted activation. The authors compared morphology, surface chemistry, textural parameters, and elemental composition of precursors (chokeberry seeds, black currant seeds, orange peels), as well as biochars (BCs) and activated carbons (ACs) obtained from them. The adsorption mechanisms of metals (copper, cadmium), metalloids (arsenic, selenium), and macromolecular compounds (bacterial exopolysaccharide, ionic polyacrylamides) on the surface of selected materials were investigated in one- and two-component systems. Consequently, the capacities of BCs and ACs prepared through direct/indirect physical activation, using conventional/microwave heating were determined. It was noted that microwave heating favoured surface development and thus enhanced adsorbent ability to bind ions or macromolecules. Direct biomass activation led to higher microporosity compared to indirect (two-stage) one, whilst CO2-consuming activation increased aromaticity and hydrophobicity of the solids. In the two-component systems, polymers could favour metal/metalloid adsorption based on complexation phenomena. However, the most efficient and environmentally safe activated carbon turned out to be the one obtained from orange peels by microwave-assisted, direct activation at 800 °C in the CO2 atmosphere.

Scalable mesoporous biochars from bagasse waste for Cu (II) removal: Process optimisation, kinetics and techno-economic analysis

As the world faces the brink of climatological disaster, it is crucial to utilize all available resources to facilitate environmental remediation, especially by accommodating waste streams. Lignocellulosic waste residues can be transformed into mesoporous biochar structures with substantial pore capacity. While biochars are considered a method of carbon dioxide removal (CDR), they are in fact an environmental double-edged sword that can be used to extract metal ions from water bodies. Biochars possess high chemical affinities through chemisorption pathways that are tuneable to specific pH conditions. This work demonstrates how biochars can be enhanced to maximise their surface area and porosity for the removal of Cu (II) in solution. It was found that bagasse derived mesoporous biochars operate preferentially at high pH (basic conditions), with the 1.18 mKOH/mSCB material reaching 97.85% Cu (II) removal in 5 min. This result is in stark contrast with the majority of biochar adsorbents that are only effective at low pH (acidic conditions). As a result, the biochars produced in this work can be directly applied to ancestral landfill sites and carbonate-rich mine waters which are highly basic by nature, preventing further metal infiltration and reverse sullied water supplies. Furthermore, to assess the value in the use of biochars produced and applied in this way, a techno-economic assessment was carried out to determine the true cost of biochar synthesis, with possible routes for revenue post-Cu being removed from the biochar.

Phallusia nigra-mediated vanadium removal from brine: Assessment and optimization

The rejected brines from desalination plants contain significant amounts of heavy metals. In this study, we evaluated the effectiveness of Phallusia nigra Savigny, 1816 (P. nigra) in removing vanadium from the rejected brines of desalination plants through the bioaccumulation process. Initial assessments revealed a remarkably high accumulation rate of vanadium in P. nigra with a bioaccumulation factor exceeding 4.7 × 104 in the tunic and 5.1 × 105 in the mantle body. Acclimation experiments demonstrated that P. nigra could survive salinities up to 56 practical salinity units (psu), temperatures of ≤32 °C, and pH of 6.5-8.5. We employed the L-16 Taguchi approach in experimental design to optimize environmental conditions for vanadium removal by P.nigra. Our results indicated that temperature has the most significant effect on increasing vanadium bioaccumulation in P. nigra, followed by salinity and pH. Under optimal conditions, the vanadium concentration reached 1892.30 ppm in the entire body of P. nigra compared to 350 ppm in natural conditions. Considering that, a high concentration of vanadium is toxic to the environment and the conventional methods of its removal from brine are costly and include the use of chemicals that pollute the environment, therefore, vanadium removal from brine using P. nigra can be considered a cost-effective and environmentally friendly method in the future, as opposed to some chemical methods.

Heavy metals immobilization and bioavailability in multi-metal contaminated soil under ryegrass cultivation as affected by ZnO and MnO2 nanoparticle-modified biochar

Pollution by heavy metals (HMs) has become a global problem for agriculture and the environment. In this study, the effects of pristine biochar and biochar modified with manganese dioxide (BC@MnO2) and zinc oxide (BC@ZnO) nanoparticles on the immobilization and bioavailability of Pb, Cd, Zn, and Ni in soil under ryegrass (Lolium perenne L.) cultivation were investigated. The results of SEM-EDX, FTIR, and XRD showed that ZnO and MnO2 nanoparticles were successfully loaded onto biochar. The results showed that BC, BC@MnO2 and BC@ZnO treatments significantly increased shoots and roots dry weight of ryegrass compared to the control. The maximum dry weight of root and shoot (1.365 g pot-1 and 4.163 g pot-1, respectively) was reached at 1% BC@MnO2. The HMs uptake by ryegrass roots and shoots decreased significantly after addition of amendments. The lowest Pb, Cd, Zn and Ni uptake in the plant shoot (13.176, 24.92, 32.407, and 53.88 µg pot-1, respectively) was obtained in the 1% BC@MnO2 treatment. Modified biochar was more successful in reducing HMs uptake by ryegrass and improving plant growth than pristine biochar and can therefore be used as an efficient and cost effective amendment for the remediation of HMs contaminated soils. The lowest HMs translocation (TF) and bioconcentration factors were related to the 1% BC@MnO2 treatment. Therefore, BC@MnO2 was the most successful treatment for HMs immobilization in soil. Also, a comparison of the TF values of plant showed that ryegrass had a good ability to accumulate all studied HMs in its roots, and it is a suitable plant for HMs phytostabilization.

Elimination of hazardous Se(IV) through adsorption-coupled reduction by iron nanoparticles embedded on mesopores of chitin obtained from waste shrimp shells

Selenium is an essential nutrient for biological function. However, there is a detrimental effect on the aquatic environment associated with higher concentrations of > 40 µg/L. The utilization of waste shrimp shells for the removal of high-concentrated selenium from wastewater is a commendable strategy in both the pollution control and waste management sectors. In the present study, a chitin-iron polymer complex hybrid material (Fe@SHC) was prepared from shrimp shell-derived hydrochar (SHC), and the synthesized composite was successfully employed to uptake selenium from wastewater. The highest removal performance of 79.18 mg/g was attained by Fe@SHC, whereas the capacity of SHC was 15.30 mg/g. It was found that the calcium content of Fe@SHC (1.98%) was lower than that of SHC (25.20%) and pHzpc of Fe@SHC was extended to 7.78 compared with that of SHC (2.00). The abundance of protonated hydroxyl (-OH2+) and amine (-NH3+) functional groups that developed through the iron co-precipitations resulted in the improved adsorption performance of Fe@SHC. XPS analysis demonstrated that the captured Se(IV) species were converted into less hazardous Se(0), which is accompanied by the electron transfer with both N-C = O (acetyl amine) and -NH2 (amine) functional groups. Adsorption kinetics disclosed that the adsorption process was governed by chemical sorption, and the Sips isotherm model provided the most accurate description of the isotherm equilibrium. This study proposed an inexpensive and environmentally friendly method for effective decontamination of Se from wastewater.

Nitrogen-rich carbon composite fabricated from waste shrimp shells for highly efficient oxo-vanadate adsorption-coupled reduction

Protein, calcium carbonate, and chitin are abundant in shrimp shells. In this study, chemical treatment followed by hydrothermal carbonization was used to synthesize the nitrogen-rich hydrochar (HSHC) from shrimp shells. The untreated hydrochar exhibited a higher amount of calcium (25.37%) and less amount of nitrogen (2.68%) with alkaline pH (9.1). Interestingly chemical pre-treatment on shrimp shells boosted the nitrogen content to 6.81% and eliminated the calcium while controlling the pH to 6.4, which was beneficial for oxo-vanadate removal. The HSHC achieved vanadium(V) adsorption capacity of 21.20 mg/g at an optimal solution pH of 3.0, whereas the pristine hydrochar performed poorly (0.66 mg/g). The abundance of oxygen and nitrogen-based functional groups that developed through the chemical treatment resulted in improved adsorption coupled reduction performance of HSHC. This study proposed an inexpensive and environmentally friendly method for converting waste shrimp shells into value-added adsorbent.

Functional biochar fabricated from red mud and walnut shell for phosphorus wastewater treatment: Role of minerals

A novel functional biochar (BC) was prepared from industrial waste red mud (RM) and low-cost walnut shell by one facile-step pyrolysis method to adsorb phosphorus (P) in wastewater. The preparation conditions for RM-BC were optimized using Response Surface Methodology. The adsorption characteristics of P were investigated in batch mode experiments, while a variety of techniques were used to characterize RM-BC composites. The impact of key minerals (hematite, quartz, and calcite) in RM on the P removal efficiency of the RM-BC composite was studied. The results showed that RM-BC composite produced at 320 °C for 58 min, with a 1:1 mass ratio of walnut shell and RM, had a maximum P sorption capacity of 15.48 mg g^-1, which was more than double that of the raw BC. The removal of P from water was found to be facilitated significantly by hematite, which forms Fe-O-P bonds, undergoes surface precipitation, and exchanges ligands. This research provides evidence for the effectiveness of RM-BC in treating P in water, laying the foundation for future scaling-up trials.

Removal of heavy metal vanadium from aqueous solution by nanocellulose produced from Komagataeibacter europaeus employing pineapple waste as carbon source

Environmental concerns have taken a center stage in our lives driving the society towards biorefinery. Bioprocess development to produce valuable products utilizing waste has its own significance in circular bioeconomy and environmental sustainability. In the present study, production of bacterial cellulose using pineapple waste as carbon source by Komagataeibacter europaeus was undertaken and it was applied for removal of vanadium, a heavy metal which is generated as waste by semiconductors industry in Taiwan. Highest yield of bacterial cellulose (BC) e.i. 5.04 g/L was obtained with pineapple core hydrolysate (HS-PC) replacing glucose in HS medium. The vanadium adsorption capacity by BC produced by HS medium was 5.24 mg/g BC at pH 4 and 2.85 mg/g BC was observed on PCH medium. BC was characterised via SEM, FTIR and XRD.

Vanadium(V) Removal from Aqueous Solutions and Real Wastewaters onto Anion Exchangers and Lewatit AF5

Adsorption abilities of weakly (Purolite A830), weakly basic/chelating (Purolite S984), and strongly basic (Lewatit MonoPlus SR7, Purolite A400TL, Dowex PSR2, Dowex PSR3) ion exchange resins of different functional groups and microporous Lewatit AF5 without functional groups towards vanadium(V) ions were studied in batch and column systems. In the batch system, the influence of the sorbent mass (0.01–0.1 g), pH (2–10), the phase contact time (1–1440 min),and the initial concentration (5–2000 mg/L) were studied, whereas in the column system, the initial concentrations (50, 100, and 200 mg/L) with the same bed volume and flow rate (0.4 mL/min) were studied. Desorption agents HCl and NaOH of 0.1–1 mol/L concentration were used for loaded sorbent regeneration. The pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models as well as the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models were used to describe kinetic and equilibrium data to acquire improved knowledge on the adsorption mechanism. The desorption efficiency was the largest using 0.5 mol/L NaOH for all sorbents under discussion. Purolite S984, Purolite A830, and Purolite A400TL, especially Purolite S984, are characterized by the best removal ability towards vanadium(V) from both model and real wastewater.

Screening the functions of modified rice straw biochar for adsorbing manganese from drinking water

The seasonal out-of-limit of manganese ions (Mn²⁺) in the drinking water reservoirs is an intractable problem to water supply, which can pose a threat to the human health. In this study, the removal of Mn²⁺ by using pristine (BC), pre-alkali (Pre-BC) and post-alkali (Post-BC) modified biochar originating from rice straw was investigated. The maximum adsorption capacities obtained for BC, Pre-BC, and Post-BC were 20.59, 28.37, and 8.06 mg g⁻¹, respectively. The Langmuir isotherm model and the pseudo-second-order kinetic model were suitable fitting models to describe the adsorption process. The investigation of adsorption functions was carried out that revealed that the predominant forces were precipitation and cation exchange with the proportions of 43.38–69.15% and 38.05–55.79%, respectively. With regard to precipitation, Mn(ii) particles (Al–Si–O–Mn and MnCO₃) and insignificantly oxidized insoluble Mn(iv) particles (MnO₂) were formed on the biochar surface. Alkali and alkaline earth metals facilitated the behavior of cation exchange, where the primary contributing ions for cation exchange were Na⁺, Mg²⁺ and Ca²⁺ during the adsorption process. These outcomes suggest that alkali pre-treated modification of biochar is practical for the application of manganese pollution control in lakes and reservoirs.

Modified biochar was used to remove Mn²⁺ from water with principal adsorption functions of precipitation and cation exchange. The MnCO₃ and Al–Si–O–Mn mainly driven precipitation and Na⁺, Mg²⁺ and Ca²⁺ primarily contributed to the cation exchange.