Biomass-based Adsorbents Research Articles

Versatile preparation strategy of negatively charged saccharide-based polymers for selective removal of cationic organic pollutants

Pursuing special negatively charged adsorbents is critical to selectively removing cationic pollutants from effluent. Herein, we proposed a versatile preparation strategy of negatively charged saccharide-based polymers using easily available saccharides as building blocks and hexachlorocyclotriphosphazene as a linker in a facile “one-step” method. Because of the existence of numerous hydroxyl groups and phosphine nitrile units in the skeleton, these polymers show selective adsorption capacity towards cationic dyes and pharmaceuticals, but not for ionic dyes and uncharged bisphenol A. Notably, β-cyclodextrin-based polymers (β-CDPs) displayed remarkable adsorption towards methylene blue (Qm, 1563 mg g−1) and promethazine (Qm, 944 mg g−1). Systematic experiments revealed that the synergy of “host-guest” inclusion, electrostatic attraction, and π-π interaction promoted the selective and efficient adsorption of cationic pollutants. Given the efficiently selective adsorption of cationic dyes and pharmaceuticals, these negatively charged saccharide-based polymers should be candidates for the adsorption of other cationic pollutants, including heavy metal ions. This work expanded the scope of the special utilization of biomass-based adsorbents for water remediation.

Adsorptive removal of antibiotic pollutants from wastewater using biomass/biochar-based adsorbents.

This study explores adsorptive removal measures to shed light on current water treatment innovations for kinetic/isotherm models and their applications to antibiotic pollutants using a broad range of biomass-based adsorbents. The structure, classifications, sources, distribution, and different techniques for the remediation of antibiotics are discussed. Unlike previous studies, a wide range of adsorbents are covered and adsorption of comprehensive classes of antibiotics onto biomass/biochar-based adsorbents are categorized as β-lactam, fluoroquinolone, sulfonamide, tetracycline, macrolides, chloramphenicol, antiseptic additives, glycosamides, reductase inhibitors, and multiple antibiotic systems. This allows for an assessment of their performance and an understanding of current research breakthroughs in applying various adsorbent materials for antibiotic removal. Distinct from other studies in the field, the theoretical basis of different isotherm and kinetics models and the corresponding experimental insights into their applications to antibiotics are discussed extensively, thereby identifying the associated strengths, limitations, and efficacy of kinetics and isotherms for describing the performances of the adsorbents. In addition, we explore the regeneration of adsorbents and the potential applications of the adsorbents in engineering. Lastly, scholars will be able to grasp the present resources employed and the future necessities for antibiotic wastewater remediation.

Gaseous formaldehyde adsorption by eco-friendly, porous bamboo carbon microfibers obtained by steam explosion, carbonization, and plasma activation

To develop an eco-friendly biomass adsorbent for indoor formaldehyde, porous bamboo carbon microfibers (BCMFs) with different types and contents of oxygen (O)-containing and nitrogen (N)-containing functional groups were firstly prepared by combining high-pressure steam explosion, carbonization, and plasma activation. The BCMF adsorbents were characterized, and their adsorption performance and mechanism were evaluated and theoretically calculated. BCMF carbonized at 800 °C (BCMF-800) showed the highest specific surface area of 526.862 m2 g−1. The surfaces of the BCMFs were etched, with many additional micro/nanoscale pores and cavities. Functional groups, including O–CO, CO, CO, quaternary N, oxidized N, pyridinic N, amine N, and pyrrolic N were successfully introduced by plasma activation at various powers and atmospheres. BCMF-800 samples activated by O2 plasma at 240 W (BCMF-800-O-240) and by N2 at 120 W (BCMF-800-N-120) exhibited the highest formaldehyde adsorption capacities (179.53 mg g−1 and 205.28 mg g−1), which were 85.90 % and 112.50 % higher than that of BCMF-800, respectively. The samples introduced by carboxyl and pyrrolic N showed the highest adsorption energies (−14.54 kcal mol−1 and −11.58 kcal mol−1) with an increase of 83.82 % and 46.40 %, respectively, compared with the control, which were proved to be the optimal O-containing and N-containing functional groups for enhancing formaldehyde adsorption. This work provides a new insight into the natural biomass-based adsorbents for gaseous formaldehyde with a clean and eco-friendly preparation and modification process.

Production of nanopore structure bio-adsorbent from wood waste through a self-sustained carbonization process for landfill leachate treatment

The discharge of leachate poses a serious risk to both surface water and groundwater from landfills. As rainwater and moisture seep through waste in landfills, it will release leachate which is high in concentration of organic matter and ammonium nitrogen. Adsorption process using activated carbon was used as one of the tertiary treatment processes in the landfill. This paper presents the utilization of biomass-based adsorbents to substitute the current activated carbon in the landfills. The carbonization process was employed using a 3-tonne self-sustained pool-type reactor, to produce micropores biochar as bio-adsorbent. The carbonization proceeds for 48 h using feedstocks with different initial moisture content of 20% and 40%. The biochar produced had microporosity ranging from 1.8 to 15.4 nm and a surface area of 192.9–231 m2/g. The use of biochar for landfill leachate treatment has shown satisfactory results, with COD, ammoniacal nitrogen, and total Kjeldahl nitrogen removal at 73%, 70%, and 97%, respectively, and heavy metals content value below the Malaysian discharge limits. This exemplifies the potential of biochar as a bio-adsorbent for treating landfill leachate and the feasibility of up-scaling biochar production from wood waste.

Simultaneous Adsorption of Cu2+ and Cd2+ by a Simple Synthesis of Environmentally Friendly Bamboo Pulp Aerogels: Adsorption Properties and Mechanisms.

The highly efficient, pollution-free and degradable biomass-based adsorbents used for the purification of wastewater are currently being highlighted in the research. Bamboo is an excellent raw material for pulp production due to its characteristics of fast growth, wide distribution and high cellulose content. In this study, a tannin/chitosan/bamboo pulp aerogel (TCPA), an environmentally friendly, renewable and low-density adsorbent, was synthesized using a simple freeze-drying method and analyzed by FTIR, XPS, SEM, TEM, TGA and surface area and porosity methods. TCPA has a large specific surface area (137.33 m2/g) and 3D porous structure, and its surface has multiple functional groups including amino, carboxyl and hydroxyl groups, which lead to a simultaneous absorption effect with Me2+ (Cu2+ and Cd2+). The maximum adsorption capacity for Cu2+ and Cd2+ of the TCPA was 72.73 mg/g and 52.52 mg/g, respectively. The adsorption processes of Me2+ by TCPA follow the pseudo-second-order model and Langmuir isotherm mode, and the adsorption processes are spontaneous and endothermic. The study provides a promising candidate for the treatment of wastewater containing heavy metal mixtures.

Preparation of low-cost aluminum-loaded longan shell adsorbent for fluoride removal: Experimental and modeling studies

Low-cost adsorbents for efficient defluoridation from drinking water have been an issue of great concern. Aluminum-loaded longan shell (LGS-Al) was prepared by a chemical co-precipitation method and was optimized following the conditions of longan shell of 5.12 g/200 mL, aluminum chloride concentration of 0.34 mol/L and water bath temperature of 68.3 °C. The as-prepared LGS-Al exhibited the amorphous structure, which is beneficial to developing functional groups of -Cl and -OH, and high reactivity of coordinatively unsaturated aluminum. The adsorption kinetic and isotherm data were better described by the pseudo-second-order and Sips models, respectively. The maximum adsorption capacity was 21.49 mg/g, which was higher than numerous reported biomass-based adsorbents. LGS-Al showed over 89.7% fluoride removal and limited leaching of aluminum and dissolved organic carbon in the initial pH range of 6.0–8.0. The exchange action of -OH and -Cl between fluoride and the formation of Al-F bonds were also confirmed by attenuated total reflectance fourier transform infrared (ATR-FTIR) spectra and X-ray photoelectron spectroscopy (XPS). The adsorption energy (Eads) of the Al-OH site for F- (−826.7 kJ/mol) was lower than that of Al-Cl, illustrating that Al-OH dominated the removal of F-. On the contrary, the Eads of Al-Cl for HF was lower (−121.8 kJ/mol), suggesting Al-Cl was a priority to react with HF. These findings indicated that LGS-Al could be a promising low-cost material for fluoride removal from drinking water.

CO2 capture from biogas by biomass-based adsorbents: A review

• Recent advances in biogas upgrading by biomass-based adsorbents are reviewed. • An overview of the production process through activation, and characteristics of adsorbent. • Recyclability and selectivity of biomass-based adsorbents for CO 2 capture have been studied. • Selection of appropriate chemical additives can be considerably enhanced the CO 2 adsorption capacities. Biogas is one of the most important renewable energy sources containing methane, carbon dioxide, and small amounts of other gases and water. Raw biogas cannot be used because CO 2 and other inert gases reduce the energy content of biogas and calorific value. Biogas upgrading significantly improves the quality of biogas by removing CO 2 . One of the leading technologies of biogas enrichment is using an adsorption method on activated carbons due to their high selectivity for removing CO 2 . Activated carbon is a good choice due to its high adsorption capacity at atmospheric pressure, lower cost, hydrophobic properties, high surface area, and the ability to modify pore structure and surface performance. On the other hand, the massive production of agricultural waste and biomass negatively affects the environment, so recycling biowaste into valuable materials is essential economically and environmentally. To recycle and convert biowaste, activated carbon is simply made through carbonization and can be used as suitable adsorbents for separating gaseous mixtures, including CH 4 /CO 2 . In this review, bio-based adsorbents were investigated in porosity, morphology, composition, selectivity, and CO 2 capture to upgrade biogas.

Adsorption behavior of three-dimensional bio-adsorbent from maize stalk pith for methylene blue

To realize the comprehensive and convenient utilization of the whole biopolymers and the natural biological structure of agro-residual stalks during the dye-wastewater treatment, we reported a simple and effective strategy to directly convert corn stalk pith (CSP) into a three-dimensional bio-adsorption material (DCSP) by degreasing treatment for purification of methylene blue (MB) wastewater by filtration. The unique anisotropic structure of DCSP provided well-developed channels and pores for mass transfer; Removal of lipids from parenchyma and vessel cells of CSP led to a larger specific surface area, promoting the exposure of adsorption sites. Due to these structural advantages, the DCSP column with 3 cm length could adsorb MB from water as high as 99.1% under the batch condition of 9 mL/min filtration rate, 5 mg/L MB solution with initial pH 6.5 at 35 ℃. As demonstrated by adsorption kinetics, isotherms and thermodynamics, this adsorption process was chemisorbed, multilayer, endothermic, spontaneous and random. According to breakthrough investigation, the prominent features like volume of MB solution at the breakthrough point, adsorbent exhaustion rate and column capacity were 3000 mL, 0.70 g/L and 7.33 mg/g, respectively, when the biofilter height was 45 cm. Its performances of adsorption capacity (7.0809 mg/g) and MB removal efficiency (0.1811 g/mg/min) during continuous process were superior to other biomass-based adsorbents previously reported. This approach provides an agricultural-waster stalks as efficient filters for dye remediation. • The defatted corn stalk pith (DCSP) acted as an excellent three-dimensional filter. • Porous structure with rich biopolymer promoted DCSP to adsorb methylene blue (MB). • The filter removed MB more than 99.0% in the batch adsorption system. • Filter had a low adsorbent exhaustion rate (0.70 g/L) via breakthrough analysis. • The adsorption rate constants of MB by DCSP was up to 0.1811 g/mg/min.

Surface Chitosan-coated Fe3O4 immobilized lignin for adsorbed phosphate radicals in solution

The design of green, efficient, and conveniently recyclable biomass-based adsorbents is of great importance, but little has been reported. Therefore, magnetic Fe3O4 doped lignin-chitosan based microspheres (CS-Li@Fe3O4) was prepared by emulsion crosslinking for phosphate removal in water. The prepared CS-Li@Fe3O4 shows a spherical structure with a diameter of 5–40 µm. Benefiting from its unique morphological structure and the abundant functional groups on the surface, CS-Li@Fe3O4 exhibits excellent phosphate adsorption capacity and is applicable in environments with a pH of 2–10. More importantly, the CS-Li@Fe3O4 retains excellent adsorption capacity after 6 adsorption/desorption cycles, demonstrating remarkable recyclability and stability. The adsorption isotherm was well described by the Langmuir model, the adsorption kinetics accords with the pseudo-first order kinetic model, which indicates that the adsorption process is monolayer chemisorption. Hence, CS-Li@Fe3O4 holds promising future for water remediation owing to its green raw material and excellent phosphate capture properties.

Adsorptive removal of lead ion from water using banana stem scutcher generated in fiber extraction process

Lignocellulosic biomass-based adsorbents for removal of heavy metal ions from water have been reported. Importantly, a solid biomass waste known as Banana Stem Scutcher (BSS) is generated in banana stem fiber (BSF) extraction from lignocellulosic rich banana stem (BS). Here, for the first time, we report BSS characterization, and its ability for adsorption of lead (Pb(II)) ion from water. The maximum adsorption capacity for Pb(II) ion removal by BSS was determined to be 179.9 mg g−1. BSS was recycled five times without any significant loss in adsorption performance. Pb(II) ion adsorption onto BSS is exothermic (ΔH = −70.55 kJ mol−1), and spontaneous (ΔG = −3.52 kJ mol−1 at 303 K) with energy of activation as, 95.95 kJ mol−1. Further, interaction between Pb(II) ion and functional groups of BSS was confirmed by XPS and FTIR results. The relative cellulose content in BSS (74.25%) was higher than the BS (57.85%), as well as BSF (60.36%). The higher accessible cellulosic content in BSS was proposed for the enhanced Pb(II) ion adsorption by BSS, compared to BS and BSF. The study highlights a low cost and chemical free, mechanical based treatment of biomass useful to produce effective biomass-based adsorbents for removal of metal ions.

Adsorption-reduction of Cr(VI) onto unmodified and phytic acid-modified carob waste: Kinetic and isotherm modeling

Carob waste (CW) is an agro-biomass material abundant in nature with potential use for eco-friendly remediation. However, like many biomass-based adsorbents, it suffers from its low adsorption capacity for organic/inorganic pollutants. Therefore, modification using physical and/or chemical means is commonly applied to improve the adsorptive properties of biomass-based adsorbents. In this study, carob waste (CW) and carob waste functionalized with phytic acid (PA-CW), as an ecofriendly product, were applied for the first time for Cr(VI) elimination. Various methods were applied for the material characterization like Fourier-transform infrared spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA and DTG), X-ray photoelectron spectroscopy (XPS), specific surface area and porosity measurements. The results proved that both CW and PA-CW own appropriate features for efficient adsorption. Bach experiments revealed that the optimum parameters for Cr(VI) (100 mg/mL) removal at 25 °C were pH 2, 0.05 and 0.025 g as adsorbent dose for CW and PA-CW, respectively, over 120 min contact time. The kinetic of adsorption was well-described by the pseudo-second order model, whereas the isotherm modeling fitted well the modified Langmuir model. CW and PA-CW achieved respectively maximum adsorption capacities of 212.4 and 387.9 mg/g, which are among the highest values so far reported for biomass-based adsorbent materials. These results confirmed that CW and PA-CW could be alternative cost-effective adsorbents even for high concentrations of Cr(VI) in industrial wastewaters along with their reduction capacity.

New optimization approach for amphoteric/magnetic ramie biosorbent in dyestuff adsorption

There is growing interest for the utilization of biomass for environmentally friendly adsorbents, and optimizing the complicated and multi-functional structure of biosorbents remains challenging. Herein, ramie waste biomass-based adsorbents with amphoteric/magnetic multi-structures via two different fabrication routes were constructed, studied and optimized to fill the gaps between multi-structure of biosorbent and performance requirements. The results show that the biosorbents exhibit excellent adsorption and magnetic recovery performance, while the biosorbent with amphiprotic-magnetic structure exhibits higher adsorption capacities for methylene blue and congo red with maximum 195.9 mg/g and 147.7 mg/g. These results are attributed to optimization of multi-structure by regulating the introduction strategy of amphiprotic groups and Fe3O4 magnetic nanoparticles. The adsorption processes of the biosorbents accord well with the pseudo-second-order kinetic model and Langmuir isotherm model, which suggests dyestuff are adsorbed via a monolayer spontaneous chemical reaction, and hydrogen bonding and electrostatic interaction are the dominant adsorption mechanisms. These demonstrate that the optimized preparation of the biosorbent improves the adsorption capacity, reusability, and stability, and provides a new perspective for the preparation of high-efficient biosorbents with multi-structures and the purification of dye-polluted wastewater.

Adsorptive Removal of Copper from Waste Water Using Biomass & Biochar Based Materials

Heavy metal contamination has been one of the primary environmental concerns for many years in most developing countries. As the industries continue to search for low-cost and efficient adsorbents to treat their effluents contaminated with these toxic metal ions, biomass-based adsorbents have gained much attention. This work exploits such ten different biomass-based adsorbents (namely, Karanja de-oiled cake, Neem de-oiled cake, Neem leaves, Moringa Leaves, Bagasse, Mango Kernel, Wheat Bran, Eucalyptus, Fly ash, and Corn cob) for adsorption of copper ions in particular. Further, selected adsorbents (namely Karanja de-oiled cake, Neem de-oiled cake, Bagasse, Wheat Bran and Mango Kernel) were taken to the next stage and modified to biochar and tested again for copper removal. Among the biomass-based adsorbents, the highest adsorption capacity was observed for Neem de-oiled cake (equal to 9.6 mg/g). While for biochar-based adsorbents, Bagasse showed the highest adsorption capacity for copper (equivalent to 13.0 mg/g).

The effects of magnetization process on methylene blue removal using magnetically modified orange peel

Whilst adsorption process is the preferred method of purifying wastewater due to its benefits, problems with the recovery of spent adsorbents are still prevalent in wastewater treatment technology. The use of magnetized biomass-based adsorbents (biosorbents) to ease the regeneration process would be a novel approach to overcome this obstacle. The magnetization of orange peel adsorbent involves a series of preparation stages. In this context, there are several parameters that may affect the magnetization of orange peel (OP) such as the ratio between FeCl3•6H2O and FeCl2•4H2O, mass of untreated orange peel (UOP), volume of NH3 solution, magnetization temperature and magnetization period. In this study, Fractional Factorial Design (FFD) was adopted to identify the significant parameters affecting two different responses namely the success of magnetization process and methylene blue (MB) dye removal. Based on the ANoVA results, the significant parameters affecting the success of the magnetization process were magnetization temperature, interaction between ratio of FeCl2:FeCl3 and volume of ammonia, and mass of OP with duration of mixing. Whereas the significant parameters affecting the MB dye removal were all five of the individual parameters, along with the interaction of amount of OP with the other four parameters, interaction between volume of ammonia with duration of mixing and with ratio of FeCl2:FeCl3, interaction between duration of mixing with temperature and ratio of FeCl2:FeCl3, and interaction between temperature and ratio of FeCl2:FeCl3. The highest recorded MB removal was 89.18%, while the lowest recorded MB removal was 38.76%. The regeneration study also showed that magnetized orange peel could be regenerated at least six times without having a significant reduction in adsorption capacity. The major functional groups of magnetized orange peel before adsorption, after adsorption and after regeneration were all similar, indicating that the spent adsorbent could be regenerated.

A green route to CO2 adsorption on biomass chitosan derived nitrogen-doped micropore-dominated carbon nanosheets by different activators

As urbanization spreads, more fossil fuels are continuously needed, though they cause air pollution to worsen. The capture and storage of CO2 has become an area of intense research interest, as it could inhibit further environmental deterioration. Herein, a novel method of synthesizing nitrogen-doped carbon nanosheet adsorbents with highly developed microporosity is proposed. Using biomass chitosan and graphitic carbon nitride (g-C3N4) as starting materials not only ensures economically favorable properties but is also makes the adsorbents ecologically friendly. The amount of nitrogen doping agent and varied activation temperatures were found to be capable of precisely controlling the pore structure and nitrogen content in the resulting product. The CO2 capture capacity of the KOH-activated adsorbent under optimum conditions (a chitosan/graphitic carbon nitride weight ratio of 6 and activation temperature of 750 °C) was determined to be 3.91 mmol/g at 298 K and 1 bar. We also chose three different potassium salt activators to use in place of the strongly caustic KOH. The test results showed that the resulting porous carbon activated by KAc exhibited CO2 uptakes of 3.54 (298 K) and 5.64 mmol/g (273 K) at 1 bar. This adsorbent also exhibited fast adsorption kinetics, remarkable recyclability, moderately isosteric heats of adsorption and good CO2 selectivity over N2. The present work will provide new inspiration for biomass-based adsorbents for CO2 capture.

Biomass-Based Adsorbents for Removal of Dyes From Wastewater: A Review

Dyes, especially azo dyes contained in wastewaters released from textile, pigment, and leather industries, are entering into natural waterbodies. This results in environmental deterioration and serious health damages (for example carcinogenicity and mutagenesis) through food chains. Physiochemical, membrane processes, electrochemical technology, advanced oxidation processes, reverse osmosis, ion exchange, electrodialysis, electrolysis, and adsorption techniques are commonly used conventional treatment technologies. However, the limitations of most of these methods include the generation of toxic sludge, high operational and maintenance costs. Thus, technological advancements are in use to remediate dyes from effluents. Adsorption using the nonconventional biomass-based sorbents is the greatest attractive alternatives because of their low cost, sustainability, availability, and eco-friendly. We present and reviewed up-to-date publications on biomass-based sorbents used for dye removal. Conceptualization and synthesizing their state-of-the-art knowledge on their characteristics, experimental conditions used were also discussed. The merits and limitations of various biosorbents were also reflected. The maximum dye adsorption capacities of various biosorbents were reviewed and synthesized in the order of the biomass type (algae, agricultural, fungal, bacterial, activated carbon, yeast, and others). Surface chemistry, pH, initial dye concentration, temperature, contact time, and adsorbent dose as well as the ways of the preparations of materials affect the biosorption process. Based on the average dye adsorption capacity, those sorbents were arranged and prioritized. The best fit of the adsorption isotherms (for example Freundlich and Langmuir models) and basic operating parameters on the removal dyes were retrieved. Which biomass-based adsorbents have greater potential for dye removal based on their uptake nature, cost-effectiveness, bulk availability, and mono to multilayer adsorption behavior was discussed. The basic limitations including the desorption cycles of biomass-based adsorbent preparation and operation for the implementation of this technology were forwarded.

Highly compressible nanocellulose aerogels with a cellular structure for high-performance adsorption of Cu(II)

Cellulose-based aerogels have considerable potential for various application due to renewable, low cost, and high availability. However, mechanical robustness and functionalization remain major challenges. Here, we synthesized a compressible, recoverable cellulose nanofiber (CNF)/carboxymethyl cellulose (CMC)/branched polyethyleneimine (BPEI) aerogel via electrostatic-modulated interfacial covalent crosslinking and freeze-drying process. The porous BPEI@CNF/CMC aerogel possessed excellent mechanical compression and high-density metal-chelating groups, which exhibited fast adsorption kinetics and high adsorption capacity (452.49 mg g−1) in static copper adsorption process. Furthermore, BPEI@CNF/CMC aerogels displayed excellent recyclability and could still reach 85% after 10 cycles. The integrated analyses of ATR-FTIR and XPS suggested that the predominant adsorption mechanism included electrostatic interaction, ion-exchange and chelation. This strategy provides a sustainable route to fabricate efficient biomass-based adsorbents for selective copper removal from water.

Synthesis Strategies, Mechanisms, and Potential Risks of Biomass-Based Adsorbents (BAs) for Heavy Metal Removal from Aqueous Environment: a Review

Synthesis Strategies, Mechanisms, and Potential Risks of Biomass-Based Adsorbents (BAs) for Heavy Metal Removal from Aqueous Environment: a Review

Polysaccharides as Support for Microbial Biomass-Based Adsorbents with Applications in Removal of Heavy Metals and Dyes.

The use of biosorbents for the decontamination of industrial effluent (e.g., wastewater treatment) by retaining non-biodegradable pollutants (antibiotics, dyes, and heavy metals) has been investigated in order to develop inexpensive and effective techniques. The exacerbated water pollution crisis is a huge threat to the global economy, especially in association with the rapid development of industry; thus, the sustainable reuse of different treated water resources has become a worldwide necessity. This review investigates the use of different natural (living and non-living) microbial biomass types containing polysaccharides, proteins, and lipids (natural polymers) as biosorbents in free and immobilized forms. Microbial biomass immobilization performed by using polymeric support (i.e., polysaccharides) would ensure the production of efficient biosorbents, with good mechanical resistance and easy separation ability, utilized in different effluents’ depollution. Biomass-based biosorbents, due to their outstanding biosorption abilities and good efficiency for effluent treatment (concentrated or diluted solutions of residuals/contaminants), need to be used in industrial environmental applications, to improve environmental sustainability of the economic activities. This review presents the most recent advances related the main polymers such as polysaccharides and microbial cells used for biosorbents production; a detailed analysis of the biosorption capability of algal, bacterial and fungal biomass; as well as a series of specific applications for retaining metal ions and organic dyes. Even if biosorption offers many advantages, the complexity of operation increased by the presence of multiple pollutants in real wastewater combined with insufficient knowledge on desorption and regeneration capacity of biosorbents (mostly used in laboratory scale) requires more large-scale biosorption experiments in order to adequately choose a type of biomass but also a polymeric support for an efficient treatment process.

Technological Advancement for Efficiency Enhancement of Biodiesel and Residual Glycerol Refining: A Mini Review

Biodiesel or known as fatty acid methyl ester (FAME), is a diesel fuel substitute derived from the transesterification reaction of triglycerides with alcohol in the presence of suitable catalyst. The demand for biodiesel is increasing due to environmental and health awareness, as well as diminishing energy security. However, the presence of impurities in biodiesel will affect engine performance by corroding fuel tubes and damaging the injectors. Common methods for the purification of biodiesel include water washing, dry washing and membrane separation. This mini review compares the technological advancement for efficient enhancement of biodiesel and glycerol refining between wet washing, dry washing (activated compound, biomass-based adsorbents and silica-based adsorbents), ion exchange and membrane separation technology. The percentage of glycerol residues, soap, alcohol and catalyst from crude biodiesel was compared to reflect the resulting biodiesel purity variation. The advantages and disadvantages of each method were also discussed.