scholarly journals Obtaining hydrogels of technical lignins

2021 ◽  
pp. 270-291
Author(s):  
Э.И. Евстигнеев ◽  
Е.В. Гриненко ◽  
А.В. Васильев
Keyword(s):  
Metal Cations ◽  
Strong Acid ◽  
Water Molecules ◽  
Chemical Plants ◽  
Weak Base ◽  
Sorption Ability ◽  
High Sorption ◽  
New Type ◽  
Low Solubility ◽  
Technical Lignins

Методами потенциометрического титрования, ИК-спектроскопии, твердофазной ЯМР-спектроскопии 13С и химического анализа исследовано гелеобразование технических лигнинов (окисленного гидролизного, сульфатного, натронного и лигносульфонатов) и лигнина Пеппера при взаимодействии с солями металлов: CaCl2, Mg(NO3)2,FeSO4, Co(NO3)2, Pb(NO3)2, Fe(NO3)3, CuSO4, AgNO3. Установлено, что способностью к гелеобразованию обладают соединения, представляющие собой соли слабого основания и сильной кислоты; катион металла имеет стандартный потенциал выше определенного значения, обладает умеренной способностью к гидролизу, а гидроксид катиона, образующийся в реакции гидролиза, имеет относительно низкую растворимость. При формировании геля образуется соединение состава R–COO–Mez+–OOC–R z = 2,3. Предложена схема межмолекулярных связей в точке образования гидрогеля лигнина, в соответствии с которой смежные молекулы лигнина связываются между собой тремя типами связей: ионной между карбоксильными группами лигнина и катионами металла, координационной между катионами металла и молекулами воды, входящими в координационную сферу; и водородными, связывающими все компоненты системы в единое целое. Гидрогели лигнина обладают высокой сорбционной способностью по отношению к тяжелым металлам, таким как свинец, железо и медь, составляющей в зависимости от содержания кислых групп в лигнине и молярной массы сорбата ~ 25–50% от массы лигнина. Это открывает возможность использовать новый вид гидрогелей лигнина для очистки сточных вод химических предприятий. Potentiometric titration, IR-spectroscopy of 13C solid-state NMR spectroscopy, and chemical analysis were used to study the gelation of technical lignins (oxidized hydrolysis, Kraft, sodium, and lignosulfonates) and Pepper lignin in interaction with metal salts: CaCl2, Mg(NO3)2,FeSO4, Co(NO3)2, Pb(NO3)2, Fe(NO3)3, CuSO4, AgNO3. It has been established that compounds that are salts of a weak base and a strong acid have the ability to gelation; the metal cation has a standard potential above a certain value, has moderate hydrolysis ability, and the cation hydroxide formed in the hydrolysis reaction has a relatively low solubility. During gel formation, a compound of the composition R–COO–Mez+–OOC–R z = 2,3 is formed. A scheme of intermolecular bonds at the point of lignin hydrogel formation is proposed, according to which adjacent lignin molecules bind to each other by three types of bonds: ionic between carboxyl groups of lignin and metal cations, coordination between metal cations and water molecules included in the coordination sphere, and hydrogen connecting all the components of the system into a single whole. Lignin hydrogels have a high sorption ability with respect to heavy metals such as lead, iron and copper, which, depending on the content of acid groups in lignin and the molar mass of the sorbate, is ~ 25–50% by weight of lignin. This opens up the possibility of using a new type of lignin hydrogels for wastewater treatment of chemical plants.

scholarly journals Synthesis of Silver-Impregnated Magnetite Mesoporous Silica Composites for Removing Iodide in Aqueous Solution

Toxics ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 175
Author(s):  
Sang-Eun Jo ◽  
Jung-Weon Choi ◽  
Sang-June Choi
Keyword(s):  
Aqueous Solution ◽  
Langmuir Isotherm ◽  
High Surface ◽  
High Surface Area ◽  
High Capacity ◽  
Maximum Adsorption Capacity ◽  
Initial Contact ◽  
Order Kinetic ◽  
Sorption Ability ◽  
High Sorption

Mag@silica-Ag composite has a high sorption ability for I− in aqueous solution due to its high surface area and strong affinity for the studied anion. The material adsorbed I− rapidly during the initial contact time (in 45 min, η = 80%) and reached adsorption equilibrium after 2 h. Moreover, mag@silica-Ag proved to selectively remove I− from a mixture of Cl−, NO3− and I−. The adsorption behavior fitted the Langmuir isotherm perfectly and the pseudo-second-order kinetic model. Based on the Langmuir isotherm, the maximum adsorption capacity of mag@silica-Ag was 0.82 mmol/g, which is significantly higher than previously developed adsorbents. This study introduces a practical application of a high-capacity adsorbent in removing radioactive I− from wastewaters.

scholarly journals Utilization of Extract of Sambang Getih Leaves (Hemigraphis colorata. Hall. F) as a Acid-Base Indicator

2020 ◽  
Vol 9 (1) ◽  
pp. 7-15
Author(s):  
Eksari Ekasari ◽  
Purnama Ningsih
Keyword(s):  
Leaf Extract ◽  
Strong Acid ◽  
Weak Base ◽  
Acid Base ◽  
Strong Base ◽  
Unique Color ◽  
Acid Base Titration ◽  
Naoh Solution ◽  
Ph Range ◽  
Color Pigment

Getih sambang leaves (Hemigraphis Colorata. Hall. F) are plants that have a distinctive and unique color, namely the upper surface of the leaf is green and the bottom of the leaf is burgundy where sambang leaves contain anthocyanin compounds. Anthocyanin is the color pigment in plants that forms the basis of the use of natural indicators. This study aims to prove whether getih cucumber leaves can be used as an acid-base indicator, to determine the type of acid-base titration that is suitable for indicators of getih cucumber leaves, and to find out what the pH-changing color route of getih cucumber leaves is. The method used is extraction, namely maceration. Wee leaves are macerated by using methanol as a solvent for 24 hours. The extract was previously tested using HCl solution and NaOH solution as a test to prove the presence of anthocyanin. The results obtained in this study, getih sambang leaf extract can be used as an indicator of acid base, and also the type of acid-base titration that is suitable for use in the indicator of getih leaf extract extract precisely on the titration of strong-base strong acid, and strong weak base-acid It is best used as a substitute for the phenolphthalein indicator. In titration of strong and weak acids and bases, it is good to be used as a substitute for the indicator of methyl orange. The pH range obtained from the getih sambang leaf extract is pH 4-7 (red-purple).

scholarly journals Copper Ions Removal from Water using A2B3 Type Hyperbranched Poly(amidoamine) Hydrogel Particles

Molecules ◽  
2019 ◽  
Vol 24 (21) ◽  
pp. 3866
Author(s):  
Hojung Choi ◽  
Youngsik Eom ◽  
Sanghwa Lee ◽  
Sang Youl Kim
Keyword(s):  
Metal Ion ◽  
Copper Ions ◽  
Suspension Polymerization ◽  
Spherical Shape ◽  
Synthetic Process ◽  
Metal Ion Removal ◽  
Hyperbranched Poly ◽  
Sorption Ability ◽  
Heavy Metal Ion Removal ◽  
High Sorption

Micrometer-sized hyperbranched poly(amidoamine) (hPAMAM) particles are prepared with a simple A2B3 type Aza–Michael addition reaction between aminoethylpiperazine (AEP) and methylenebisacrylamide (MBA) in an inverse suspension polymerization condition. The synthesized particles exhibited surprisingly high Cu2+ sorption capacity (0.223g/g) for a solid-type absorbent. In addition to the high sorption ability of the particle, its simple synthetic process and convenience, due to its micrometer-sized spherical shape and recyclability, make it a practical and attractive absorbent for heavy metal ion removal from aqueous solutions.

scholarly journals Cell Wall Saturation Limit and Selected Properties of Thermally Modified Oak Wood and Cellulose

Forests ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 640 ◽  
Author(s):  
Richard Hrčka ◽  
Viera Kučerová ◽  
Tatiana Hýrošová ◽  
Vladimír Hönig
Keyword(s):  
Molecular Weight ◽  
Cell Wall ◽  
Average Molecular Weight ◽  
Chemical Components ◽  
Water Molecules ◽  
Strong Negative Correlation ◽  
Oak Wood ◽  
Saturation Limit ◽  
Sorption Ability ◽  
Weighing Method

The interaction of water and oak wood is common in outdoor expositions and will remain a probable occurrence in the future. New insights into the recognition of a cell wall saturation limit are presented by a double-weighing method at 20 °C. The cell wall saturation limit, as the property of thermally modified oak wood, is significantly influenced by different treatment temperatures (20, 160, 180, 210 and 240 °C) on a 5% alpha level. A significantly higher equilibrium moisture content was reached by thermally modified oak wood at a temperature of 20 °C and relative humidity of 65% after its equilibrium in the water-in-reservoir. Moreover, the results are used in the treatment of woodchips to produce cellulose or decomposition of thermally modified wood to its basic chemical components. The investigated properties of cellulose revealed its relationship with water. The number of water molecules bonded to a cellulose chain was correlated with other measured compositions: average molecular weight, total crystalline index, lateral order index and polydispersity index. Analyses showed that there was a strong negative correlation between lateral order index and average molecular weight. The same was true between total crystalline index and average molecular weight. The rest of the properties were positively correlated with the number of water molecules bonded to glucopyranose. The results revealed the possible regeneration of a wood sorption ability after heat treatment and the stability of cellulose in such process.

Salts of aromatic carboxylates: the crystal structures of nickel(II) and cobalt(II) 2,6-naphthalenedicarboxylate tetrahydrate

2001 ◽  
Vol 34 (6) ◽  
pp. 710-714 ◽  
Author(s):  
James A. Kaduk ◽  
Jason A. Hanko
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Crystal Packing ◽  
Geometry Optimization ◽  
Metal Cations ◽  
Carboxyl Groups ◽  
Water Molecules ◽  
Triclinic Space Group ◽  
Aromatic Carboxylates ◽  
Monte Carlo Simulated Annealing

The crystal structures of isostructural 2,6-naphthalenedicarboxylate tetrahydrate salts of nickel(II) and cobalt(II) have been determined using Monte Carlo simulated annealing techniques and laboratory X-ray powder diffraction data. These compounds crystallize in the triclinic space groupP\bar{1}, withZ= 2;a= 10.0851 (4),b= 10.9429 (5),c= 6.2639 (3) Å, α = 98.989 (2), β = 87.428 (3), γ = 108.015 (2)°,V= 649.32 (5) Å3for [Ni(C12H6O4)(H2O)4], anda= 10.1855 (6),b= 10.8921 (6),c= 6.2908 (5) Å, α = 98.519 (4), β = 87.563 (4), γ = 108.304 (3)°,V= 655.28 (8) Å3for [Co(C12H6O4)(H2O)4]. The water-molecule H atoms were located by quantum chemical geometry optimization usingCASTEP. The structure consists of alternating hydrocarbon and metal/oxygen layers parallel to theacplane. Each naphthalenedicarboxylate anion bridges two metal cations; each carboxyl group is monodentate. The resulting structure contains infinite chains parallel to [111]. The octahedral coordination sphere of the metal cations containstranscarboxylates and four equatorial water molecules. The carboxyl groups are rotated by 15–20° out of the naphthalene plane. The metal/oxygen layers are characterized by an extensive hydrogen-bonding network. The orientations of the carboxyl groups are determined by the formation of short (O...O = 2.53 Å) hydrogen bonds between the carbonyl O atoms and theciswater molecules. Molecular mechanics energy minimizations suggest that coordination and hydrogen-bonding interactions are most important in determining the crystal packing.

New Type of C-Pivot Tripode Ligands for Complexation towards Alkali Metal Cations

1995 ◽  
Vol 24 (1) ◽  
pp. 51-52 ◽  
Author(s):  
Yohji Nakatsuji ◽  
Kohji Kita ◽  
Araki Masuyama ◽  
Toshiyuki Kida
Keyword(s):  
Alkali Metal ◽  
Metal Cations ◽  
Alkali Metal Cations ◽  
New Type

Mechanistic studies in strong acids. VIII. Hydrolysis mechanisms for some thiobenzoic acids and esters in aqueous sulfuric acid, determined using the excess acidity method

1982 ◽  
Vol 60 (24) ◽  
pp. 3061-3070 ◽  
Author(s):  
Robin A. Cox ◽  
Keith Yates
Keyword(s):  
Sulfuric Acid ◽  
Proton Transfer ◽  
Strong Acid ◽  
Weak Acid ◽  
Medium Composition ◽  
Hydrolysis Rate ◽  
Water Molecules ◽  
Aqueous Sulfuric Acid ◽  
Ion Formation ◽  
Rate Determining Step

The excess acidity method has been applied to hydrolysis rate data, obtained as a function of medium composition, for four thiobenzoic acids, thioacetic acid, eight ethyl thiolbenzoates, and eight ethyl thionbenzoates in aqueous sulfuric acid. The mechanistic behaviour thus revealed has both similarities to and differences from that of a typical ester like ethyl benzoate, which gives benzoic acid by an A-2 reaction involving two water molecules in weak acid, and by A-1 acylium ion formation in strong acid. The thioacids follow this behaviour, except that the A-2 process involves three water molecules, and that the mechanistic changeover occurs in 60% rather than 80% acid. The A-2 process for the ethyl thiolbenzoates is slow; the major hydrolysis mechanism is acylium ion formation, not in an A-1 reaction but by a concerted A-SE2 process involving both proton transfer to sulfur and carbon–sulfur bond breaking. The major proton transfer agent is the undissociated sulfuric acid molecule. The thionbenzoate esters, in contrast, undergo very fast A-2 hydrolysis; so fast, in fact, that the initial protonation of sulfur is the rate-determining step in acids more dilute than about 62% w/w. It appears that proton transfer to sulfur is a comparatively slow process.

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