Efficiency of chitosan–algal biomass composite microbeads at heavy metal removal

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.

Phycoremediation of heavy metals and production of biofuel from generated algal biomass: a review

Due to human activity and natural processes, heavy metal contamination frequently affects the earth's water resources. The pollution can be categorized as resistant and persistent since it poses a significant risk to terrestrial and marine biological systems and human health. Because of this, several appeals and demands have been made worldwide to try and clean up these contaminants. Through bioremediation, algal cells are frequently employed to adsorb and eliminate heavy metals from the environment. Bioremediation is seen as a desirable strategy with few adverse effects and low cost. Activities and procedures for bioremediation involving algal cells depend on various environmental factors, including salinity, pH, temperature, the concentration of heavy metals, the amount of alga biomass, and food availability. Additionally, the effectiveness of removing heavy metals from the environment by assessing how environmental circumstances affect algal activities. The main issues discussed are (1) heavy metal pollution of water bodies, the role of algal cells in heavy metal removal, the methods by which algae cells take up and store heavy metals, and the process of turning the algae biomass produced into biofuel. (2) To overcome the environmental factors and improve heavy metals bioremediation, many strategies are applied, such as immobilizing the cells, consortium culture, and using dry mass rather than living cells. (3) The processes for converting produced algal biomass into biofuels like biodiesel and biomethanol. The present study discusses the life cycle assessment and the limitations of biofuel products from algae biomass.

Developing nano-micro size chitosan beads using imidazolium-based ionic liquid: A perspective

The aggressive search for unique materials in recent years has put forward chitosan and modified-chitosan as materials with unique structural and morphological characteristics for various important applications. Just as imidazolium-based ionic liquids are the commonly applied ionic liquids (ILs) type for chitosan modifications for various applications, their further modifications into beads for enhancing their properties is now gaining most attention. However, most of the currently prepared imidazolium ILs modified-chitosan beads are not in nano size due to preparation difficulties. In response to this and referencing the research works in the literature, the possible breakthrough directions including synthesis routes, and physical and mechanical transformation processes are proposed. These procedures are expected to provide certain theoretical and empirical basis, as well as technical guide for developing nano-micro size chitosan beads using imidazolium based ILs.

A systematic review on carbohydrate biopolymers for adsorptive remediation of copper ions from aqueous environments-Part B: Isotherms, thermokinetics and reusability

The presence of copper in aquatic environment is a serious threat for human health and ecosystem conservation. Adsorption is a powerful, operable and economic method for remediation of copper ions from aqueous phase. Carbohydrate biopolymers have emerged as promising, effective and environmental-friendly adsorbents for copper remediation. In part A of this review, different types of carbohydrate biopolymer adsorbents were surveyed focusing on prevalent and novel synthesis and modification methods. In current work (part B of the review), isothermal, thermodynamic and kinetic aspects of the copper adsorption by carbohydrate-based adsorbents as well as the regeneration and reusability of the biopolymer adsorbents are overviewed. Adsorption capacity, time required for equilibrium (adsorption rate), thermal-sensitivity of the adsorption, favorability extent, and sustainability of the adsorbents and adsorption processes are valuable and useful outcomes, resulted from the thermokinetic and reusability investigations. Such considerations are critical for the process design and scale up regarding technical, economical and sustainability of the adsorption process.

Ionic Cross-Linking Fabrication of Chitosan-Based Beads Modified with FeO and TiO2 Nanoparticles: Adsorption Mechanism toward Naphthalene Removal in Seawater from Cartagena Bay Area

Polycyclic aromatic hydrocarbons (PAHs) are complex molecules produced by the thermal decomposition of organic matter in anthropogenic activities. Novel composites with enhanced physicochemical properties aim to overcome limitations such as adsorption capacity, affinity, and stability for PAHs adsorption. Composites based on chitosan are promising due to the good biocompatibility and adsorption properties. This study focuses on the facile preparation of chitosan beads modified with iron oxide (FeO) and titanium dioxide (TiO₂) nanoparticles via ionic cross-linking (Ch-FeO/TiO₂). FeO and TiO₂ were synthesized performing co-precipitation and green chemistry methods, respectively. The characterization evidenced the formation of Ch-FeO/TiO₂ with good crystallinity, excellent thermal stability, and superparamagnetic response, attributed to the presence of FeO and TiO₂ nanoparticles. High thermal stability up to 270 °C was related to the cross-linked chitosan network. The enhanced adsorption mechanism of Ch-FeO/TiO₂ was determined by removing naphthalene from water and seawater samples. The Ch-FeO/TiO₂ showed a higher adsorption capacity of 33.1 mg/g compared to 29.8 mg/g of the unmodified chitosan (un-Ch) beads. This is due to the higher functional surface area of 27.13 m²/g, compared to that of 0.708 m²/g for un-Ch. We found a rapid adsorption rate of 240 min and the maximum adsorption capacity of 149.3 mg/g for Ch-FeO/TiO₂. A large number of actives sites allows for increasing the naphthalene molecules interaction. Adsorption in seawater samples from Cartagena Bay (Colombia) exhibits an outstanding efficiency of up to 90%. These results suggest a promising, cheap, and environmentally friendly composite for remediation of water sources contaminated with complex compounds.

In situ preparation of magnetic hydrochar by co-hydrothermal treatment of waste vinasse with red mud and its adsorption property for Pb(II) in aqueous solution

Herein, a new magnetic hydrochar was prepared through co-hydrothermal treatment of vinasse with red mud, two abundant industrial wastes, and its adsorption property was evaluated on Pb(II), selected model ion in aqueous solution. During co-hydrothermal process, Fe₂O₃ species in red mud was reduced to Fe₃O₄ form, hereby, in situ magnetization of hydrochar was achieved, which was confirmed by characterization studies. Produced hydrochar with porous structure (V_total = 0.071 cm³/g and BET surface area = 23 m²/g) had saturation magnetization (44.7 emu/g), providing easier separation from water by a magnet. Maximum Pb(II) adsorption was favored at pH ≥ 5.0 within 120 min of equilibrium time and Freundlich isotherm model was preferable. The contribution percentage of different mechanisms including cation-exchange (40.8 %), (electrostatic attraction + "cation-π" interaction) (31.2 %), precipitation (25.4 %) and complexation (2.6 %) to overall Pb(II) adsorption indicated that cation-exchange was the dominant mechanism. Finally, application to fortified real water demonstrated that in situ magnetic hydrochar produced by suggested approach was successful at adsorptive removal of Pb(II) from water with no matrix effects.

Sorption of Cu(II), Zn(II) and Pb(II) Ions in an Aqueous Solution on the PVC-Acetylacetone Composites

The possibility of removing Cu(II), Zn(II) and Pb(II) ions by sorption on new PVC-based composite materials with different contents of acetylacetone (acac) and porophor was investigated. Composites were characterized using a scanning electron microscope and by infrared spectral analysis (FTIR). Sorption tests were conducted at 20 °C. It has been shown that the equilibrium is established in about 4 h. The reduction in ion concentration in the solution depended on the content of both acac and porophor in the composite. The maximal reduction in ion concentration ranged from 8% to 91%, 10–85% and 6–50% for Cu(II), Zn(II) and Pb(II) ions, respectively, depending on the composite composition. The best results were obtained for the composite containing 30% w/w of acac and 10% of porophor. For this composite, the sorption capacity after 4 h sorption for Zn(II), Cu(II) and Pb(II) ions was 26.65, 25.40, and 49.68 mg/g, respectively. Kinetic data were best fitted with a pseudo–second-order equation.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Application of hybrid bead, persimmon leaf and chitosan for the treatment of aqueous solution contaminated with toxic heavy metal ions

In this study, hybrid beads, which are made by mixing persimmon leaf and chitosan, was used to remove Pb(II) and Cd(II) from aqueous solution. According to the Fourier transform infrared spectrometry (FT-IR) analysis, the hybrid bead has a structure that enables the easy adsorption of heavy metals because it has carboxylic, carbonyl groups, O-H carboxylic acid, and bonded -OH groups. The adsorption of Pb(II) and Cd(II) by hybrid beads was more suitable with the Langmuir isothermal adsorption and showed an ion exchange reaction which occurred in the uneven adsorption surface layer. The maximum adsorption capacity of Pb(II) and Cd(II) was determined to be 278.68 mg/g and 87.91 mg/g, respectively. Furthermore, the adsorption removal process of Pb(II) and Cd(II) using hybrid beads is a spontaneous exothermic reaction and the affinity of the adsorbed material for the adsorbent is excellent. Hybrid beads are inexpensive, have a high removal efficiency of heavy metals, and are environmentally friendly.

The potentiality of cross-linked fungal chitosan to control water contamination through bioactive filtration

Water contamination, with heavy metals and microbial pathogens, is among the most dangerous challenges that confront human health worldwide. Chitosan is a bioactive biopolymer that could be produced from fungal mycelia to be utilized in various applied fields. An attempt to apply fungal chitosan for heavy metals chelation and microbial pathogens inhibition, in contaminated water, was performed in current study. Chitosan was produced from the mycelia of Aspergillus niger, Cunninghamella elegans, Mucor rouxii and from shrimp shells, using unified production conditions. The FT-IR spectra of produced chitosans were closely comparable. M. rouxii chitosan had the highest deacetylation degree (91.3%) and the lowest molecular weight (33.2kDa). All chitosan types had potent antibacterial activities against Escherichia coli and Staphylococcus aureus; the most forceful type was C. elegans chitosan. Chitosan beads were cross-linked with glutaraldehyde (GLA) and ethylene-glycol-diglycidyl ether (EGDE); linked beads became insoluble in water, acidic and alkaline solutions and could effectively adsorb heavy metals ions, e.g. copper, lead and zinc, in aqueous solution. The bioactive filter, loaded with EGDE- A. niger chitosan beads, was able to reduce heavy metals' concentration with >68%, and microbial load with >81%, after 6h of continuous water flow in the experimentally designed filter.

Preparation and characterization of novel polysulfone-red mud composite capsules for the removal of fluoride from aqueous solutions

This study is the first investigation on the encapsulation of red mud by a polysulfone matrix through a phase inversion process to obtain composite capsules for the removal of fluoride from aqueous solutions.