Sorption Cycles Research Articles

Batch Study of Cadmium Biosorption by Carbon Dioxide Enriched Aphanothece sp. Dried Biomass

The conventional method for cadmium removal in aqueous solutions (1–100 mg/L) is ineffective and inefficient. Therefore, a batch biosorption reactor using a local freshwater microalga (originating from an urban lake, namely, Situ Rawa Kalong-Depok) as dried biosorbent was tested. Biosorbent made from three kinds of cyanobacterium Aphanothece sp. cultivars (A0, A8, and A15) were used to eliminate cadmium (Cd2+) ions in aqueous solution (1–7 mg/L). The biosorbents were harvested from a photobioreactor system enriched with carbon dioxide gas of 0.04% (atmospheric), 8%, and 15% under continuous light illumination of about 5700–6000 lux for 14 d of cultivation. Produced dried biosorbents had Brunauer–Emmet–Teller (BET) surface area ranges of 0.571–1.846 m2/g. Biosorption of Cd2+ was pH and concentration dependent. Sorption was spontaneous (ΔG = −8.39 to −10.88 kJ/mol), exothermic (ΔH = −41.85 to −49.16 kJ/mol), and decreased randomness (ΔS = −0.102 to −0.126 kJ/mol. K) on the interface between solid and liquid phases when the process was completed. The kinetic sorption data fitted best to the pseudo-second-order model (k2 = 2.79 × 10−2, 3.96 × 10−2, and 4.54 × 10−2 g/mg.min). The dried biosorbents of A0, A8, and A15, after modeling with the Langmuir and Dubinin–Radushkevich isotherm models, indicated that cadmium binding occurred through chemisorption (qmax, D-R = 9.74 × 10−4, 4.79 × 10−3, and 9.12 × 10−3 mol/g and mean free energy of 8.45, 11.18, and 11.18 kJ/mol) on the monolayer and homogenous surface (qmax, Langmuir of 12.24, 36.90, and 60.24 mg/g). In addition, the results of SEM, EDX, and FTIR showed that there were at least nine functional groups that interacted with Cd2+ (led to bond formation) after biosorption through cation exchange mechanisms, and morphologically the surfaces changed after biosorption. Biosorbent A15 indicated the best resilient features over three cycles of sorption–desorption using 1 M HCl as the desorbing eluent. These biosorbents can be a potent and eco-friendly material for treating aqueous wastewater.

Efficient removal of uranium, cadmium and mercury from aqueous solutions using grafted hydrazide-micro-magnetite chitosan derivative

Magnetic chitosan microparticles are functionalized by grafting a new hydrazide derivative to produce HAHZ-MG-CH, which is applied to the sorption of metal cations. The functionalization (appearance of new groups) and synthesis mechanisms are confirmed using elemental analyses, FTIR and XPS spectrometry, TGA and EDX analysis, SEM observation and titration. HAHZ-MG-CH bears high nitrogen content (≈ 10.9 mmol N g−1). Maximum sorption capacities at pH 5 reach up to 1.55 mmol U g−1, 1.82 mmol Hg g−1 and 2.67 mmol Cd g−1. Sorption isotherms are preferentially fitted by the Langmuir model. In acidic solutions, the sorbent has a marked preference for Hg(II) over U(VI) and Cd(II), while at mild pH uranyl species are preferentially bound. The sorbent has a lower affinity for Cd(II) in multicomponent solutions. Sorption occurs within 60 min of contact. The pseudo-first-order rate equation fits well kinetic profiles. HCl solutions (0.5 M) successfully desorb all the metal ions (yield exceeds 97% at the first cycle). The sorbent can be recycled for 5 cycles of sorption and desorption: the loss in efficiencies does not exceed 8%. The sorbent removes Hg(II), Cd(II) and Pb(II) from local contaminated groundwater at levels compatible with irrigation and livestock uses but not enough to reach the levels for drinking water regulations.

Insights and utility of cycling-induced thermal deformation of calcium-based microporous material as post-combustion CO2 sorbents

On the quest of finding ideal sorbent for post-combustion CO2 capture, calcium-based sorbent seems to have the potential, but often it cannot sustain its reactivity, especially after repeated cycle of sorption. This work aims to unravel the controlling factors in carbonation reaction and thermal-induced deformation of skeleton pore network that limits the CO2 absorptivity of calcium-based sorbent. Through precise measurement of CO2 absorption activity using TGA/DSC and a series of characterization, this study paves the way for the development of next-generation CaO sorbent that has high CO2 uptake capacity and thermal stability. Key findings include CaO particles with severe point defects contribute to fast CO2 absorption activity. The transformation from CaCO3 phase to CaO phase from organic precursor is 4 times higher than the inorganic precursor. Decomposition of calcium formate is thermally stable regardless of calcination temperature. Citrate-based structure precursor is able to produce homogeneous nanosized CaO particle. Shifting of reaction controlling regime from fast carbonation reaction to diffusion limited stage happened at Thiele modulus of 1.35. Lastly, first stage of fast carbonation reaction will take place at CaO sorbent’s surface with proximate zero activation energy and second stage of slow carbonation reaction is controlled by high activation energy of ion diffusion behavior in CaCO3 ionic crystals at product diffusion layer. Future research direction can focus on reproducing long periodical citrate-like structural precursor using sol-gel method to mimic the behavior of calcium formate and calcium citrate to form nano-sized CaO particles with thermally stable crystal structure.

Modified Merrifield’s resin materials used in capturing of Pb(II) ions in water

In this paper, we report the synthesis of three new adsorbent materials for the recovery of Pb(II) ions in aqueous media by immobilization of the 3′,4′,5,7-pentahydroxyflavone (quercetin) on the Merrifield resin. The Merrifield’s resin was modified with different length alkyl chain spacers arms (oxi-alkyl-OH with six, seven and ten methylene groups) to immobilize quercetin on the resin. Materials characterization was performed by IR spectroscopy, molecular fluorescence and elemental microanalysis. The conversion rates showed yields higher than 95%. The adsorption properties of the Pb(II) ions showed that the highest retention is observed into the range of 0.64 to 1.21 mg g−1 in a dynamic regime at pH 5. The optimal concentration of the HNO3 eluent was 1 mol l−1 with 10 ml as the elution volume, and the pre-concentration factor was 4. Finally, a 93% of Pb(II) recovered was obtained on water supply employing the MR6Q resin, which also present stable behaviour and reusability in sorption and desorption cycles. These results encourage the use of these materials for pre-concentration and determination of Pb (II) in water.

Uranium(VI) and zirconium(IV) sorption on magnetic chitosan derivatives – effect of different functional groups on separation properties

AbstractBACKGROUNDThe recovery of metal ions from aqueous solutions for environmental preservation or resource saving requires the development of new sorbents with enhanced separation properties. A new process has been designed for the functionalization of magnetic chitosan microparticles with grafting of either amidoxime (AO‐AHC) or hydrazinyl amine (HZ‐AHC). Their sorption properties have been tested for the recovery of uranium(VI) and zirconium(IV) from aqueous solutions.RESULTSA wide range of analytical tools is used for characterizing not only the chemical modifications but also the interaction mode between the sorbent and target metal ions; including elemental analysis and titration, Fourier‐transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS) characterizations, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations, energy‐dispersive X‐ray spectroscopy (EDX) analysis and textural characterization. The optimum pH values were found in the range 4–5. The maximum sorption capacities depend on the metal and the kind of functionalization: up to 1.38 mmol U g−1 for AO‐AHC and up to 1.96 mmol Zr g−1 for HZ‐AHC. The small size of magnetic particles limits the contribution of diffusion mechanisms in the overall control of uptake kinetics and the equilibrium is reached within 40–60 min. Metal desorption is highly effective (almost quantitative over five successive cycles of sorption and desorption) using 0.3 M hydrochloric acid solutions.CONCLUSIONAO‐AHC sorbent is more selective than HZ‐AHC in terms of separation of uranium(VI) from zirconium(IV), especially at pH close to 4. The results obtained in the treatment of acidic ore leachates confirm these trends. © 2019 Society of Chemical Industry

Thermodynamic analyses on hybrid sorption cycles for low-grade heat storage and cogeneration of power and refrigeration

This paper investigates three ways of coupling a solid/gas sorption refrigeration cycle with a Rankine cycle to create innovative hybrid cycles enabling power and refrigeration cogeneration with intrinsic energy storage. A new methodology has been developed to analyze these hybrid cycles and assess five relevant performance criteria (required heat source temperature, energy efficiency, exergy efficiency, power production ratio, and exergy storage density). Screening of 103 reactive salts implemented in the different hybrid cycle configurations highlights the most favorable configuration and reagent to meet the requirements of various applications. Analyses show that energy and exergy efficiencies can reach 0.61 and 0.40, respectively. Exergy storage density ranges from 142 to 640 kJ/kgNH3 when the heat source temperature is increased from 107 °C to 250 °C.

Water Vapor Adsorption-Desorption Behavior of Surfactant-Coated Starch Particles for Commercial Energy Wheels.

This study reports on the adsorption (dehumidification)–desorption (humidification) behavior of cetylpyridinium bromide (CPB) coated starch particles (SPs), denoted as SP-CPB, as a potential desiccant material for air-to-air energy exchangers. CPB is a cationic surfactant with antibacterial activity that can be used to modify the surface properties of SPs, especially at variable CPB loading levels (SP-CPB0.5, SP-CPB2.5, and SP-CPB5.0, where the numeric suffix represents the synthetic loading level of CPB in mM). The SP-CPB0.5 sample displayed optimal surface area and pore structure properties that was selected for water sorption isotherm studies at 25 °C. The CPB-coated SPs sample (SP-CPB0.5) showed an improved water vapor uptake capacity compared to unmodified starch (SPs) and other desiccant systems such as high amylose starch (HAS15) and silica gel (SG13). Single-step and cyclic water vapor sorption tests were conducted using a small-scale exchanger coated with SP-CPB0.5. The calculated latent effectiveness values obtained from direct measurements using cyclic tests (65.4 ± 2%) agree closely with the estimated latent effectiveness from single-step tests (64.6 ± 2%) at controlled operating conditions. Compared to HAS15- and SG13-coated exchangers, the SP-CPB0.5-coated exchanger performed much better at controlled operating conditions, along with improved longevity due to the CPB surface coating. The presence of CPB did not attenuate the uptake properties of native SPs. Latent effectiveness of SP-CPB0.5-coated exchanger was enhanced (5–30% higher) over that of the SG13- or HAS15-coated exchangers, according to the wheel angular speed. This study reports on a novel and sustainable SP-CPB0.5 material as a promising desiccant coating with tunable uptake and surface properties with potential utility in air-to-air energy exchangers for ventilation systems.

Effects of nano-composites (FeB, FeB/CNTs) on hydrogen storage properties of MgH2

The carbon nanotubes (CNTs), the as-prepared FeB nanoparticles and the CNTs decorated with FeB nanoparticles (denoted as FeB/CNTs) are introduced respectively into MgH2 system by wet milling with cyclohexane (CYH), and results show that wet milling with CYH and adding dopants (CNTs, FeB or FeB/CNTs) both improve the hydrogen storage properties of MgH2. The MgH2−10 wt% FeB/CNTs (CYH) composite shows the best properties. Its onset dehydrogenation temperature is 196 °C, which is 114 °C lower than that of the MgH2 (without CYH). Furthermore, the hydrogen desorption activation energy of MgH2−10 wt% FeB/CNTs (CYH) is reduced to 89.7 kJ/mol. The composite starts to absorb hydrogen at temperature as low as 39 °C, and can take up 6.2 wt% of H2 at 150 °C and 5 MPa H2 within 10 min. The hydrogen sorption cycling measurements indicate that the kinetics of the MgH2−10 wt% FeB/CNTs (CYH) composite keeps almost stable within 20 cycles, and the hydrogen storage capacity remains at 6.02 wt% (93% of the initial capacity) after 20 cycles. It is believed that the in-situ formed Fe and B as the active species and the good thermal conductivity of CNTs help enhance the hydrogen storage properties of the MgH2.

New highly-percolating alginate-PEI membranes for efficient recovery of chromium from aqueous solutions

Highly percolating membranes are prepared by the interaction of polyethylenimine and alginate (with glutaraldehyde crosslinking). SEM illustrates the macroporous structure of the material. The material is characterized by FTIR before and after chromate anions sorption. Batch-simulated continuous sorption experiments revealed that the maximum sorption occurred at pH 2 and the flow rate has limited effect on sorption efficiency. Uptake kinetics and sorption isotherms are well fitted by the pseudo-second-order rate and Sips equations, respectively. Maximum sorption is found close to 314 mg g−1. Competition effects from Ca(II), Cu(II), Cl−, NO3−, and SO42− are investigated to evaluate sorbent selectivity. The membranes are applied to remediate a simulate of Cr(VI) contaminated electroplating wastewater. Successive cycles of sorption and desorption show that the membranes maintain sorption capacity higher than 200 mg Cr g−1 for both Cr(VI) and total chromium for the first two cycles. These new highly percolating membranes have promising performances for Cr(VI) removal.

Unraveling the Sorption Mechanism of CO2 in a Molecular Crystal without Intrinsic Porosity.

The facile uptake of CO2 gas in a nonporous molecular crystal constituted by long molecules with carbazole and ethynylphenyl moieties was reported in experiments recently. Herein, the mechanism of gas uptake by this crystal is elucidated using atomistic molecular simulations. The uptake of CO2 is shown to be facilitated by (i) the capacity of the crystal to expand in volume because of weak intermolecular interactions, (ii) the parallel orientation of the long molecules in the crystal, and (iii) the ability of the molecule to marginally bend, yet not lose crystallinity because of the anchoring of the terminal carbazole groups. The retention of crystallinity upon sorption and desorption cycles is also demonstrated. At high enough pressures, near-neighbor CO2 molecules sorbed in the crystal are found to be oriented parallel to each other.

2D/3D Assemblies of Amine-Functionalized Graphene Silica (Templated) Aerogel for Enhanced CO2 Sorption.

This work investigates the one-pot facile synthesis of novel 2D/3D assemblies containing graphene silica (templated) aerogel sorbents for CO2 capture, a greenhouse gas of major global concern. In this synthesis, 3D silica (templated) aerogels were formed along the planes of 2D graphene sheets, resulting in 2D/3D assemblies of flake-like shapes. The templates were burnt off from the 2D/3D assembly, leaving a mesoporous cavity which increased with the carbon chain length used in the synthesis method. As such, morphological features related to surface area and total pore volume increased significantly by over 80% as compared to blank (no template) samples and reached maximum values of 734 m2 g-1 and 0.42 cm3 g-1, respectively. The increase in total pore volume allowed for higher content of impregnated amine into the 2D/3D assembly followed by a freeze-drying method. The CO2 sorption capacity of the amine-functionalized 2D/3D assemblies reached high values at 4.9 mmol g-1 (mass over weight ratio), equivalent to 11.67 mmol cm-3 (mass over total pore volume ratio). The amine-functionalized 2D/3D assemblies were stable over 10 cycles of CO2 sorption and desorption. Further, heat of sorption results were generally low, with the lowest value reaching 59 kJ mol-1. These results are desirable for the deployment of 2D/3D assemblies as sorbents to capture CO2.

Extraordinary air water harvesting performance with three phase sorption

Water scarcity is a current concern and a future problem. Air-water harvesting (AWH) is a novel proposed solution to provide enough water for human-being's needs especially in remote areas. However, the sorbent material is one of the challenging components of these systems. Generally, a proper sorbent must have a high water uptake capacity, a low regeneration temperature and an easy replacement structure, suitable to deploy in the bed. Here we synthesized three active carbon felt composites with a layer structure and analyzed their potential for being used in AWH systems. The performance of these ACFs composites concerning three different salts was investigated. Experimental results showed that the highest capacity is 2.9 g water per g sorbent at 70% of RH without any leakage. Also, pore parameters, non-equilibrium and equilibrium adsorption, regeneration temperature, recyclability and thermal diffusivity of samples were tested. The thermodynamic cycle of the system is studied, and a three-phase sorption cycle is proposed in this study. The detailed analysis reveals that the presence of the combined use of adsorption-absorption process can improve the sorption capacity extensively. The experimental and theoretical studies proved that these composites are very promising materials for water harvesting applications. To demonstrate these materials capability, a prototype is proposed which adopts these materials as its desiccant. This small prototype automatically could harvest 1.51 g of fresh water per cycle per g of sorbent at RH of 70%, without any human involvement.

High-Power Adsorption Heat Pumps Using Magnetically Aligned Zeolite Structures.

Adsorption heat pumps offer a clean, zero-emission technology for universally applicable cooling or heating utilizing water as a refrigerant and waste or renewable heat as driving energy instead of electricity. Despite their attractive environmentally friendly prospects, the broader application of such classes of heat pumps has not yet been possible, mainly because of the low power density of adsorption heat exchangers and the corresponding large size and high cost of the adsorption heat pumps. We report an inexpensive route for the fabrication of zeolite coatings with high adsorption power density based on the bottom-up assembly of colloids directed by magnetic and capillary forces. Such an assembly process relies on the chaining of oil droplets under an external magnetic field during deposition of the coating, followed by the formation of a percolating network of bridged adsorbent particles upon drying. This results in vertically open channels and thermal bridges that facilitate directed mass and heat transport across the structured zeolite coating during sorption cycles. By reaching up to 3.3-fold higher performance than their unstructured counterparts using readily available zeolite as an adsorbent material, the architectured coatings produced through this facile, upscalable approach hold great potential for next-generation adsorption heat pumps.

Synthesis of polyaminophosphonic acid-functionalized poly(glycidyl methacrylate) for the efficient sorption of La(III) and Y(III)

After synthesis of parent PGMA micro-particles by dispersion polymerization method, diethylenetriamine (DETA) is grafted on the polymer (DETA-PGMA). In the last step, methylene phosphonic groups are grafted on DETA-PGMA by reaction of phosphonic acid groups onto amine functions in the presence of formaldehyde to produce polyaminophosphonic acid sorbent (PPA-PGMA). The sorbent is characterized by elemental analysis, FTIR spectrometry, XPS, XRD, TG-TDA and SEM-EDX analyses. The sorption properties of the material are tested for the sorption of La(III) and Y(III): the effect of pH on sorption performance is investigated before studying uptake kinetics, sorption isotherms (and thermodynamics), metal desorption and sorbent recycling. Maximum sorption capacities reach up to 0.79 mmol La g−1 and 0.73 mmol Y g−1 at pH 5 (optimum initial pH value). Sorption isotherms are characterized by a saturation plateau: the Langmuir equation fits well data. The sorption on micron-sized particles is fast and equilibrium is reached within 3–4 h: the kinetic profiles are modelled by the Crank equation (resistance to intraparticle diffusion) though the pseudo-first order rate equation fits well experimental data. Nitric acid (0.5 M) solutions can be used for metal recovery and the sorbent is re-used for at least 6 cycles of sorption and desorption with limited decrease in performance (less than 7%). The sorbent has a preference at pH 5 for La(III) vs. Y(III) but the selectivity coefficient is not high enough for potentiating the selective separation of the two metals.

Water sorption properties, diffusion and kinetics of zeolite NaX modified by ion-exchange and salt impregnation

Zeolite NaX is one of the most popular water sorption materials for dehumidification, thermal energy storage and sorption cooling. In this paper, zeolite NaX is modified by magnesium chloride to achieve ion-exchange (zeolite NaMgX) and salt impregnation (zeolite NaX/MgCl2) with the aim of improving water sorption capacity and thermal performance. The pore structure, desorption heat, water equilibrium sorption property, adsorption kinetics and cycling stability of zeolite NaX, NaMgX and NaX/MgCl2 were studied to evaluate their potential for sorption application. Experimental results show the zeolite NaMgX has stronger hydrophilic and can improve the water sorption capacity from 0.17 g/g to 0.20 g/g at 2500 Pa. The zeolite NaX/MgCl2 with 12.6 wt% salt confined inside the meso-/macro-pore, can improve the water sorption capacity from 0.17 g/g to 0.26 g/g with sorption heat of 842 J/g. The sorption rate of zeolite NaX/MgCl2 is much lower than that of pure zeolite NaX, while zeolite NaMgX has a slight lower sorption rate than pure zeolite NaX. The diffusivity of zeolite NaX is in the range of 8.03 × 10−10–1.97 × 10−9 m2/s at 1000–2500 Pa, while zeolite NaMgX and zeolite NaX/MgCl2 have diffusivities in the range of 5.22 × 10−10–1.73 × 10−9 m2/s and 3.76 × 10−10–9.87 × 10−10 m2/s respectively. The diffusivities of different zeolite samples increase with temperature which can be described by activated energy factor, and the relation between diffusivity and pressure is strongly coupled with the equilibrium equation. The modified zeolites have good thermal stabilities and no obvious uptake loss after ten adsorption-desorption cycles, making them feasible, scalable and economical for sorption thermal energy storage and cooling applications.

A semi-industrial preparation procedure of CaO-based pellets with high CO2 uptake performance

A semi-industrial preparation procedure of CaO-based sorbent pellets was developed for the calcium looping process. First, Ca12Al14O33, was incorporated into CaO-based sorbents to enhance the cyclic stability via a wet mixing method. Then, spray-drying technology, was chosen to obtain well-mixed precursor powders quickly and efficiently in an industrialized mode. Finally, the CaO-based pellets were fabricated via an extrusion-spheronization method for practical industrial application and doped with three novel types of pore formers (urea, polyethylene glycol and polyvinyl alcohol). It is found that the sorbent pellets with 5 wt% urea possess the optimal CO2 uptake. Even under the oxy-fuel calcination condition, the sorbent pellets still held a 0.29 g CO2/g sorbent capacity at the 25th cycle, which was approximately 10 times as high as that of limestone pellets. Moreover, the sorbent pellets exhibited a high anti-attrition capacity, with a weight loss of below 0.8% after 3000 rotations. Therefore, the sorbent pellets derived from the foregoing semi-industrial synthesis procedure can simultaneously satisfy the requirements of cyclic sorption performance, industrial production and practical industrial application. This work provides a possibility for the production of highly efficient CaO-based sorbent pellets, to some extent, which can pave the way for the application of calcium looping process.

2D/3D amine functionalised sorbents containing graphene silica aerogel and mesoporous silica with improved CO2 sorption

This work investigates the performance of amine functionalised 2D/3D sorbents for CO2 capture. The 2D/3D structures were based on a combination of flake-like reduced graphene-silica oxide (G-Si) aerogel and rod-like mesoporous silica SBA-15. The G-Si aerogel formed mainly silica microporous structures which enveloped graphene sheets. The SBA-15 displayed the classical rod-like mesoporous features with high pore volume. The addition of G-Si aerogel to SBA-15 for the amine functionalised samples significantly reduced the combined total surface area and pore volume. Interestingly, the CO2 sorption capacity increased and peaked for samples containing G-Si aerogel/SBA-15 at 1:20 mass ratio (4.7 wt%), though declining thereafter. This counterintuitive effect of increasing CO2 sorption capacity but decreasing surface area and pore volume was attributed to the special morphological features of the 2D/3D sorbent assembly. At these optimal conditions, the flake-like G-Si aerogel was well intercalated with the rod-like SBA-15. As a result, the inter-particle space formed between the flake-like and rod-like assembly accommodated TEPA which facilitate the mass transfer and reaction between the amine groups and CO2. These special 2D/3D morphological features delivered high CO2 sorption capacity of 6.02 mmol g−1. The 2D/3D sorbents were also very stable under sorption and desorption cycles whilst heat of sorption were up to 22% lower than the analogue 3D SBA-15/TEPA sorbent.

Пионеры синтеза ионообменных материалов. 120 лет со дня рождения Александра Борисовича Даванкова (1899-1971)

Представлена история создания отечественных ионообменников с конца 1930 гг. по начало 1970 гг. на основе анализа работ лаборатории ионитов МХТИ им. Д.И. Менделеева. Представлена биография Александра Борисовича Даванкова – одного из отечественных пионеров ионного обмена, а также ранее неизвестные факты биографий и научные работы некоторых ученых, внесших заметный вклад в данную область. Впервые проанализированы ключевые публикации и патенты этого периода с историко-научной точки зрения.

Композиционные сорбирующие изделия на основе силикагеля для осушки газовых сред

В работе рассматриваются сорбционные изделия, предназначенные для удаления влаги из газовых сред, на основе силикагеля марки КСМГ и полимерных матриц – водных растворов полиакриламида и поливинилового спирта. Определены физико-химические и прочностные характеристики разработанных материалов в различных условиях их эксплуатации. На протяжении 40 циклов осушкивлажного воздуха (90% отн. при (24±1)оС) до остаточного влагосодержания 0.3 г/м3 исследовались сорбционные свойства полученных изделий. Установлено, что применение поливинилового спирта в качестве матрицы позволяет продлить срок службы блочного изделия в сравнении с насыпной шихтой силикагеля при сохранении прочностных характеристик материала.

Heavy metal sorption in biosorbents – Using spent grain from the brewing industry

The sorption properties of brewer's spent grain (BSG) were assessed in terms of its usefulness in removing heavy metals from solutions. The specific objectives of the investigation involved studying sorption equilibrium and kinetics, assessing the influence of other cations on sorption efficiency, and examining the possibility of bed regeneration. The studies were carried out in a static system, with a constant ratio of solution volume to biosorbent mass, and using a flow through system. The affinity of metal cations to BSG functional groups was established and increased in the series: Mn2+ ≈ Zn2+ < Ni2+ < Cd2+ < Cu2+ < Pb2+. The BSG's sorption capacities (mmol g−1), determined using the Langmuir model, ranged from 0.020 (Mn) to 0.041 (Pb), with measurements of uncertainty not exceeding 20%. It was determined that a relatively high concentration of calcium cations (7.5 mmol L−1) versus copper cation concentration (0.03 mmol L−1) in solution, restricted the sorption efficiency by approximately 80%. The optimum pH of the solution used to carry out the sorption was determined to be within the range of 4.5–5.5. It was found that the functional groups of the BSG lose their efficacy over consecutive sorption and desorption cycles due to being blocked, or due to their chemical decomposition. This indicated that the proper interpretation of the results requires a statistical assessment of the measurements of uncertainty and of the uncertainty of determination of the sorption parameters.