Phycoremediation of lithium ions from aqueous solutions using free and immobilized freshwater green alga Oocystis solitaria: mathematical modeling for bioprocess optimization

Utilization of Electrodeionization for Lithium Removal

In this work, usage of a hybrid polymeric ion exchange resin and a polymeric ion exchange membrane in the same unit to remove Li⁺ from aqueous solutions was reported. The effects of the applied potential difference to the electrodes, the flow rate of the Li-containing solution, the presence of coexisting ions (Na⁺, K⁺, Ca²⁺, Ba²⁺, and Mg²⁺), and the influence of the electrolyte concentration in the anode and cathode chambers on Li⁺ removal were investigated. At 20 V, 99% of Li⁺ was removed from the Li-containing solution. In addition, a decrease in the flow rate of the Li-containing solution from 2 to 1 L/h resulted in a decrease in the removal rate from 99 to 94%. Similar results were obtained when the concentration of Na₂SO₄ was decreased from 0.01 to 0.005 M. The selectivity test showed that the simultaneous presence of monovalent ions such as Na⁺ and K⁺ did not change the removal rate of Li⁺. However, the presence of divalent ions, Ca²⁺, Mg²⁺, and Ba²⁺, reduced the removal rate of Li⁺. Under optimal conditions, the mass transport coefficient of Li⁺ was found as 5.39 × 10^-4 m/s, and the specific energy consumption was found as 106.2 W h/g LiCl. Electrodeionization provided stable performance in terms of the removal rate and transport of Li⁺ from the central compartment to the cathode compartment.

Process optimization and modeling of Cd2+ biosorption onto the free and immobilized Turbinaria ornata using Box-Behnken experimental design

The release of effluents containing cadmium ions into aquatic ecosystems is hazardous to humans and marine organisms. In the current investigation, biosorption of Cd2+ ions from aqueous solutions by freely suspended and immobilized Turbinaria ornata biomasses was studied. Compared to free cells (94.34%), the maximum Cd2+ removal efficiency reached 98.65% for immobilized cells obtained via Box-Behnken design under optimized conditions comprising algal doses of 5.04 g L-1 and 4.96 g L-1, pH values of 5.06 and 6.84, and initial cadmium concentrations of 25.2 mg L-1 and 26.19 mg L-1, respectively. Langmuir, Freundlich, and Temkin isotherm models were suitably applied, providing the best suit of data for free and immobilized cells, but the Dubinin-Radushkevich model only matched the immobilized algal biomass. The maximum biosorption capacity of Cd2+ ions increased with the immobilized cells (29.6 mg g-1) compared to free cells (23.9 mg g-1). The Cd2+ biosorption data obtained for both biomasses followed pseudo-second-order and Elovich kinetic models. In addition, the biosorption process is controlled by film diffusion followed by intra-particle diffusion. Cd2+ biosorption onto the free and immobilized biomasses was spontaneous, feasible, and endothermic in nature, according to the determined thermodynamic parameters. The algal biomass was further examined via SEM/EDX and FTIR before and after Cd2+ biosorption. SEM/EDX analysis revealed Cd2+ ion binding onto the algal surface. Additionally, FTIR analysis confirmed the presence of numerous functional groups (hydroxyl, carboxyl, amine, phosphate, etc.) participating in Cd2+ biosorption. This study verified that immobilized algal biomasses constitute a cost-effective and favorable biosorbent material for heavy metal removal from ecosystems.

Algal-based system for removal of emerging pollutants from wastewater: A review

The bioremediation of emerging pollutants in wastewater via algal biotechnology has been emerging as a cost-effective and low-energy input technological solution. However, the algal bioremediation technology is still not fully developed at a commercial level. The development of different technologies and new strategies to cater specific needs have been studied. The existence of multiple emerging pollutants and the selection of microalgal species is a major concern. The rate of algal bioremediation is influenced by various factors, including accidental contaminations and operational conditions in the pilot-scale studies. Algal-bioremediation can be combined with existing treatment technologies for efficient removal of emerging pollutants from wastewater. This review mainly focuses on algal-bioremediation systems for wastewater treatment and pollutant removal, the impact of emerging pollutants in the environment, selection of potential microalgal species, mechanisms involved, and challenges in removing emerging pollutants using algal-bioremediation systems.

Biosorption of cationic Hg2+ and Remazol brilliant blue anionic dye from binary solution using Gelidium corneum biomass

Remazol brilliant blue (RBB) is an anthraquinone anionic dye that has several commercial uses, especially in the textile industries and is well-known for its detrimental impacts on marine life and the surrounding ecosystem. Mercury (Hg2+) is also one of the most severe hazardous environmental contaminants due to its bioaccumulation through the food chain and high toxicity to the human embryo and fetus. The biosorption potential of Gelidium corneum biomass for bioremoval of Hg2+ and RBB dye simultaneously from binary mixture was assessed. The effects of initial pH, contact time, Hg2+, RBB, and biomass concentrations on the biosorption process were investigated in 50 batch experiments using a Face-centered central composite design. The maximum removal percentage of Hg2+ (98.25%) was achieved in the run no. 14, under optimum experimental conditions: 200 mg/L Hg2+, 75 mg/L RBB, pH 5. At 30 °C, 4 g/L algal biomass was used, with a contact time of 180 min. Whereas, the maximum removal percentage of RBB (89.18%) was obtained in the run no. 49 using 200 mg/L Hg2+, 100 mg/L RBB, pH 5, 4 g/L algal biomass and 180 min of contact time. FTIR analysis of Gelidium corneum biomass surface demonstrated the presence of many functional groups that are important binding sites responsible for Hg2+ and RBB biosorption. SEM analysis showed apparent morphological alterations including surface shrinkage and the appearance of new shiny adsorbate ion particles on the Gelidium corneum biomass surface after the biosorption process. The EDX study reveals an additional optical absorption peak for Hg2+, confirming the role of Gelidium corneum biomass in Hg2+ biosorption. In conclusion, Gelidium corneum biomass has been shown to be an eco-friendly, sustainable, promising, cost-effective and biodegradable biosorbent to simultaneously biosorb Hg2+ and RBB dye from aquatic ecosystems.

The Upcoming 6Li Isotope Requirements Might Be Supplied by a Microalgal Enrichment Process

Lithium isotopes are essential for nuclear energy, but new enrichment methods are required. In this study, we considered biotechnology as a possibility. We assessed the Li fractionation capabilities of three Chlorophyte strains: Chlamydomonas reinhardtii, Tetraselmis mediterranea, and a freshwater Chlorophyte, Desmodesmus sp. These species were cultured in Li containing media and were analysed just after inoculation and after 3, 12, and 27 days. Li mass was determined using a Inductively Coupled Plasma Mass Spectrometer, and the isotope compositions were measured on a Thermo Element XR Inductively Coupled Plasma Mass Spectrometer. The maximum Li capture was observed at day 27 with C. reinhardtii (31.66 µg/g). Desmodesmus sp. reached the greatest Li fractionation, (δ⁶ = 85.4‰). All strains fractionated preferentially towards ⁶Li. More studies are required to find fitter species and to establish the optimal conditions for Li capture and fractionation. Nevertheless, this is the first step for a microalgal nuclear biotechnology.

Bioprocess development for biosorption of cobalt ions and Congo red from aquatic mixture using Enteromorpha intestinalis biomass as sustainable biosorbent

Because of the increased amount of cobalt and Congo red dye effluents attributable to the industrial operations, the capacity of Enteromorpha intestinalis biomass as a sustainable source to achieve significant biosorption percent for both pollutants from dual solution was assessed. A fifty batch FCCCD experiments for biosorption of cobalt ions and Congo red dye were performed. The complete removal of Congo red dye was obtained at 36th run using an initial pH value of 10, 1.0 g/L of Enteromorpha intestinalis biomass, 100 and 200 mg/L of Congo red and cobalt for a 20-min incubation time. Meanwhile, a cobalt removal percent of 85.22 was obtained at 35th run using a neutral pH of 7.0, 3.0 g/L of algal biomass, 150 and 120 mg/L of Congo red, and cobalt for a 60-min incubation time. For further illustration and to interpret how the biosorption mechanism was performed, FTIR analysis was conducted to inspect the role of each active group in the biosorption process, it can be inferred that -OH, C-H, C=O, O-SO3- and C-O-C groups were mainly responsible for Co2+ adsorption of from aqueous dual solution. Also, scan electron microscope revealed the appearance of new shiny particles biosorbed on E. intestinalis surface after the biosorption process. EDS analysis proved the presence of Co2+ on the algal surface after the biosorption process.

Production of Algal Biomass and High-Value Compounds Mediated by Interaction of Microalgal Oocystis sp. KNUA044 and Bacterium Sphingomonas KNU100

There is growing interest in the production of microalgae-based, high-value by-products as an emerging green biotechnology. However, a cultivation platform for Oocystis sp. has yet to be established. We therefore examined the effects of bacterial culture additions on the growth and production of valuable compounds of the microalgal strain Oocystis sp. KNUA044, isolated from a locally adapted region in Korea. The strain grew only in the presence of a clear supernatant of Sphingomonas sp. KNU100 culture solution and generated 28.57 mg/l/d of biomass productivity. Protein content (43.9 wt%) was approximately two-fold higher than carbohydrate content (29.4 wt%) and lipid content (13.9 wt%). Oocystis sp. KNUA044 produced the monosaccharide fucose (33 μg/mg and 0.94 mg/l/d), reported here for the first time. Fatty acid profiling showed high accumulation (over 60%) of polyunsaturated fatty acids (PUFAs) compared to saturated (29.4%) and monounsaturated fatty acids (9.9%) under the same culture conditions. Of these PUFAs, the algal strain produced the highest concentration of linolenic acid (C18:3 ω3; 40.2%) in the omega-3 family and generated eicosapentaenoic acid (C20:5 ω3; 6.0%), also known as EPA. Based on these results, we suggest that the application of Sphingomonas sp. KNU100 for strain-dependent cultivation of Oocystis sp. KNUA044 holds future promise as a bioprocess capable of increasing algal biomass and high-value bioactive by-products, including fucose and PUFAs such as linolenic acid and EPA.

Simultaneous bioremediation of cationic copper ions and anionic methyl orange azo dye by brown marine alga Fucus vesiculosus

Textile wastewater contains large quantities of azo dyes mixed with various contaminants especially heavy metal ions. The discharge of effluents containing methyl orange (MO) dye and Cu2+ ions into water is harmful because they have severe toxic effects to humans and the aquatic ecosystem. The dried algal biomass was used as a sustainable, cost-effective and eco-friendly for the treatment of the textile wastewater. Box-Behnken design (BBD) was used to identify the most significant factors for achieving maximum biosorption of Cu2+ and MO from aqueous solutions using marine alga Fucus vesiculosus biomass. The experimental results indicated that 3 g/L of F. vesiculosus biomass was capable of removing 92.76% of copper and 50.27% of MO simultaneously from aqueous solution using MO (60 mg/L), copper (200 mg/L) at pH 7 within 60 min with agitation at 200 rpm. The dry biomass was also investigated using SEM, EDS, and FTIR before and after MO and copper biosorption. FTIR, EDS and SEM analyses revealed obvious changes in the characteristics of the algal biomass as a result of the biosorption process. The dry biomass of F. vesiculosus can eliminate MO and copper ions from aquatic effluents in a feasible and efficient method.

Rotatable central composite design versus artificial neural network for modeling biosorption of Cr6+ by the immobilized Pseudomonas alcaliphila NEWG-2

Heavy metals, including chromium, are associated with developed industrialization and technological processes, causing imbalanced ecosystems and severe health concerns. The current study is of supreme priority because there is no previous work that dealt with the modeling of the optimization of the biosorption process by the immobilized cells. The significant parameters (immobilized bacterial cells, contact time, and initial Cr6+ concentrations), affecting Cr6+ biosorption by immobilized Pseudomonas alcaliphila, was verified, using the Plackett-Burman matrix. For modeling the maximization of Cr6+ biosorption, a comparative approach was created between rotatable central composite design (RCCD) and artificial neural network (ANN) to choose the most fitted model that accurately predicts Cr6+ removal percent by immobilized cells. Experimental data of RCCD was employed to train a feed-forward multilayered perceptron ANN algorithm. The predictive competence of the ANN model was more precise than RCCD when forecasting the best appropriate wastewater treatment. After the biosorption, a new shiny large particle on the bead surface was noticed by the scanning electron microscopy, and an additional peak of Cr6+ was appeared by the energy dispersive X-ray analysis, confirming the role of the immobilized bacteria in the biosorption of Cr6+ ions.

Bioprocessing optimization for efficient simultaneous removal of methylene blue and nickel by Gracilaria seaweed biomass

The pollution of water by heavy metal ions and dyes, particularly from industrial effluents, has become a global environmental issue. Therefore, the treatment of wastewater generated from different industrial wastes is essential to restore environmental quality. The efficiency of Gracilaria seaweed biomass as a sustainable biosorbent for simultaneous bioremoval of Ni²⁺ and methylene blue from aqueous solution was studied. Optimization of the biosorption process parameters was performed using face-centered central composite design (FCCCD). The highest bioremoval percentages of Ni²⁺ and methylene blue were 97.53% and 94.86%; respectively, obtained under optimum experimental conditions: 6 g/L Gracilaria biomass, initial pH 8, 20 mg/L of methylene blue, 150 mg/L of Ni²⁺ and 180 min of contact time. Fourier Transform Infrared Spectroscopy (FTIR) spectra demonstrated the presence of methyl, alkynes, amide, phenolic, carbonyl, nitrile and phosphate groups which are important binding sites involved in Ni²⁺ and methylene blue biosorption process. SEM analysis reveals the appearance of shiny large particles and layers on the biosorbent surface after biosorption that are absent before the biosorption process. In conclusion, it is demonstrated that the Gracilaria seaweed biomass is a promising, biodegradable, ecofriendly, cost-effective and efficient biosorbent for simultaneous bioremoval of Ni²⁺ and methylene blue from wastewater effluents.

Eco-friendly approach for biosorption of Pb2+ and carcinogenic Congo red dye from binary solution onto sustainable Ulva lactuca biomass

Dyes constitute an important group of organic contaminants and are recognized for its harmful effects on the aquatic environments and humans. Heavy metals are also the largest group of inorganic pollutants due to their accumulation in the environment, contaminate food chains and cause adverse effects on the living organisms. Biosorption capacity of Ulva lactuca biomass was assessed in batch experiments for simultaneous removal of Pb2+ and Congo red dye from binary solution. The process variables effects on Congo red dye and Pb2+ removal percentages were explored by performing 50 experiments using Face-centered central composite design. The highest removal percentages of Congo red dye (97.89%) and Pb2+ (98.78%) were achieved in the run no. 24, using 100 mg/L Congo red dye, 200 mg/L Pb2+, 3 g/L algal biomass, initial pH 6 and contact time was 120 min at 30 °C. FTIR analysis of the algal biomass showed the existence of many functional groups responsible for the biosorption process. After the biosorption process, SEM analysis revealed obvious morphological changes including surface shrinkage and the presence of new glossy Pb2+ particles, and the EDS spectra reveals presence of additional Pb2+ peak confirming the capacity of Ulva lactuca biomass to remove Pb2+ from binary solution.

Bioprocessing strategies for cost-effective simultaneous removal of chromium and malachite green by marine alga Enteromorpha intestinalis

A large number of industries use heavy metal cations to fix dyes in fabrication processes. Malachite green (MG) is used in many factories and in aquaculture production to treat parasites, and it has genotoxic and carcinogenic effects. Chromium is used to fix the dyes and it is a global toxic heavy metal. Face centered central composite design (FCCCD) has been used to determine the most significant factors for enhanced simultaneous removal of MG and chromium ions from aqueous solutions using marine green alga Enteromorpha intestinalis biomass collected from Jeddah beach. The dry biomass of E. intestinalis samples were also examined using SEM and FTIR before and after MG and chromium biosoptions. The predicted results indicated that 4.3 g/L E. intestinalis biomass was simultaneously removed 99.63% of MG and 93.38% of chromium from aqueous solution using a MG concentration of 7.97 mg/L, the chromium concentration of 192.45 mg/L, pH 9.92, the contact time was 38.5 min with an agitation of 200 rpm. FTIR and SEM proved the change in characteristics of algal biomass after treatments. The dry biomass of E. intestinalis has the capacity to remove MG and chromium from aquatic effluents in a feasible and efficient manner.