Heavy Metal Chlorides Research Articles

Novel Strategy for Efficient Recovery of CuO-Based Multiple-Metals from Copper Smelter Dust toward CO2 Electrocatalytic Reduction.

Copper smelter dust, a typical hazardous waste that is abundant in valuable heavy metals, holds the potential to be regarded as a promising resource. This study introduces a new approach that integrates chlorination roasting and cascade condensation to efficiently recover heavy metals from copper smelter dust. The findings demonstrate the successful separation of heavy metals (Cu, Pb, and Zn) as chlorides at nearly 100% efficiency while also effectively converting trivalent arsenic (As(III)) into pentavalent arsenic (As(V)) and immobilizing it in the roasting residues, thereby reducing environmental risk. Through the utilization of thermogravimetric mass spectrum analysis and thermodynamic equilibrium calculations, the chlorination process for heavy metals was investigated, revealing both direct and indirect chlorination processes. Additionally, the study resulted in the development of a CuO-based multiple-metals electrocatalyst from the oxidized roasting-recovered heavy metal chlorides, exhibiting significantly enhanced catalytic activity and faradaic efficiency for the electroreduction of CO2 into CO and CH4 compared to pure CuO electrocatalyst under similar electrocatalytic conditions. Overall, this work presents a sustainable and scalable method and new insights for addressing environmental risks while repurposing copper smelter dust.

Effective stabilization of heavy metals in solid waste and sludge pyrolysis using intercalated-exfoliated modified vermiculite: Experiment and simulation study

Pyrolysis is effective in reducing the volume of solid waste and sludge, and produces less pollutants than incineration and landfill, but the process still suffers from heavy metal pollution. Four types of intercalated-exfoliated modified vermiculite (UIV, DIV, TIV and 3IV) were prepared using urea, dimethylsulfoxide, tributyl phosphate and 3-aminopropyltriethoxysilane as intercalators for the control of Cd, Cr, Cu, Pb and Zn in municipal sewage sludge (MSL), paper mill sludge (PML), municipal domestic waste (MWA) and aged refuse (AFE). The larger the interlayer spacing of the vermiculite, the more favorable the retention of heavy metals. 3IV was the most effective additive, with an average retention of more than 75 % of all heavy metals at 450 ℃ for the four raw materials. Cr, Cu, Pb and Zn were all at low potential ecological risk (Pr), while Cd was moderate or considerable Pr, and the addition of 3IV reduced the Pr. Distribution of intercalators between vermiculite interlayers was haphazard, and interlayer spacing results were close to those of the experiment (except for tributyl phosphate). The reactive electrons mainly flowed from the Highest Occupied Molecular Orbital (HOMO) of vermiculite flakes to the Lower Unoccupied Molecular Orbital (LUMO) of heavy metal chlorides. In contrast, the reactive electrons mostly flowed from the HOMO of heavy metal oxides to the LUMO of vermiculite flakes. Heavy metal oxides were more readily adsorbed on vermiculite flakes than heavy metal chlorides, and the adsorption capacity of Cr and Zn was stronger than that of Cd, Pb and Cu.

Fate of Cl and chlorination mechanism during municipal solid waste incineration fly ash reutilization using thermal treatment: a review.

Safe and sustainable treatment of municipal solid waste incineration fly ash (MSWI FA) is urgently needed worldwide because of its high heavy metals, dioxin, and chlorine (Cl) contents. Thermal treatment is widely considered as a promising method for treating MSWI FA owing to its high toxic content removal efficiency and resource recovery; however, residual Cl is a concurrent critical problem faced during reutilisation of thermal treatment products. This review summarises the innovative thermal treatment methods of MSWI FA, such as those employed in production of cement, lightweight aggregates, glass slag, and metal alloys. The characteristics of Cl in MSWI FA, removal rate, transformation of water-soluble Cl into water-insoluble Cl, and the effect of different influencing factors such as temperature, composition, superheated steam, and mechanical pressure were analysed. The volatilization and decomposition of NaCl, KCl and CaClOH dominates Cl removal; however, the degradation of organic Cl and heavy metal chlorination volatilization process that generate HCl and heavy metal chlorides, respectively, also contributed to Cl removal. To promote the reutilisation of MSWI FA-based products, the leaching behaviour of residual Cl in products obtained by different thermal treatments was investigated.

Simultaneous realization of heavy metal Cd solidification and chloride separation in municipal solid waste incineration fly ash: Mechanism and DFT analysis

The solidification of heavy metals and the separation-recycling of chloride salts are effective approaches for the safe disposal of municipal solid waste incineration (MSWI) fly ash. This study achieved the solidification of the excessive heavy metal Cd by transforming MSWI fly ash into a solidified body mainly composed of ettringite, while also purifying the calcium and sulfate ions in the chloride solution. The research results demonstrate that the introduction of aluminum ions rapidly decreases the pH value of the MSWI fly ash reaction system. By adjusting the reaction system to a pH value of 11.50, the conversion rate of calcium ions reaches 99.68%, the separation rate of chloride reaches 95.99%, and the solidification rate of heavy metal Cd reaches 98.92%. Density functional theory (DFT) calculations indicate that the vacancy formation at the Ca-2 position of ettringite and Cd entering the vacancy has a higher probability. The combination of DFT calculations and experiments validates that heavy metal Cd leads to charge redistribution, increased interplanar spacing, and decreased thermal stability of ettringite. The concentration of calcium ions in the solution decreases to 22.64 mg/L, achieving efficient recovery of sodium chloride and potassium chloride in a shorter process. The ettringite-based solidified body contains 0.87% chloride ions, showing potential for resource utilization in cement-based materials.

Experimental and theoretical study to control the heavy metals in solid waste and sludge during pyrolysis using modified expanded vermiculite

Na+/K+/Mg2+/Ca2+ expansion–modified vermiculite and calcination expansion (700 °C, 800 °C and 900 °C)–modified vermiculite (700-Mg-V, 800-Mg-V and 900-Mg-V) were prepared as additives to control the emission of five heavy metals (Zn, Cr, Cu, Pb, and Cd) during the pyrolysis of municipal sewage sludge, paper mill sludge, municipal domestic waste, and aged refuse. Mg2+-Modified vermiculite obtained via thermally activated calcination at 800 °C retained 65% of heavy metals from all raw materials at 450 °C. Zn, Cr, and Cu retained nearly 90%. Although modified vermiculite could reduce the ecological risk, Cd had an ecological risk level higher than Zn, Cr, Cu, and Pb. The fine textural properties, laminated morphology, and expansion capacity of modified vermiculite were positively correlated with its retention of heavy metals. Heavy metals interacted with the (002) surface of vermiculite, and the reactions were mainly concentrated near the 17-O and surrounding atoms. The heavy-metal monomers were less capable of binding to the (002) surface of vermiculite than the oxides and chlorides of heavy metals. The effect of heavy-metal oxides and chlorides binding to the (002) surface of vermiculite was related to heavy metals.

Experimental and theoretical-based study of heavy metal capture by modified silica-alumina-based materials during thermal conversion of coal at high temperature combustion

Heavy metals emitted from coal combustion can easily pose many threats. In this study, five modified additives based on kaolin were prepared for reducing the emission of heavy metals from high temperature coal combustion and characterized by XRD, FT-IR, XRF, BET, SEM and zeta potential. The heavy metal retention characteristics of the additives under high temperature (900–1300 °C) coal combustion were investigated by static and dynamic experiments, and the results showed that pseudo-boehmite-metakaolin (BMK) was the most effective additive, and the ability of heavy metal capture was Cr > Zn > Pb > Cd, and the dynamic experiments were better than the static experiments. The quantum chemical models of heavy metals (monomers, oxides and chlorides), kaolin and adsorbent-active substances were developed and optimized, and the adsorption energy was calculated. The morphological changes of the active substances were taken into account in the simulation, and new mathematical models for adsorption energy calculation were proposed, which effectively solved the extreme results of adsorption energy calculation and made a comprehensive evaluation of heavy metal adsorption for the whole studied temperature range system. The mechanism of heavy metal adsorption on the active substance was further investigated by the simulations. Heavy metal atoms can form covalent or ionic bonds with O atoms of the active substance, Cl atoms of heavy metal chlorides can be covalently bonded or non-bonded with Al atoms of the active substance, and O atoms of heavy metal oxides can combine with Al atoms of the active substance to form ionic bonds. This study sheds new light on the control of heavy metals in high-temperature coal combustion, the methods for the optimization of simulation and the adsorption mechanism of heavy metals on relevant reactive substances. The method has a promising potential for large-scale application due to its simple preparation, low cost and significant effect.

Experimental study on adsorption of PbCl2 and CdCl2 on kaolin modified by leachates from municipal solid waste incineration power plant

Six kinds of waste liquids produced in the treatment process of leachate in a waste incineration plant were used to improve the adsorption effect of raw kaolin on heavy metal chloride. The capture performances of these modified kaolin on PbCl2 and CdCl2 vapor were investigated in a two-stage fixed bed combustor. The results indicated that the adsorption effects of raw kaolin on PbCl2 and CdCl2 were improved in some experimental groups, main effective component was Na+ in the leachate, but the influences did not change regularly with the increase in the concentration of Na + introduced into kaolin. The adsorbents formed by modifying 10 g kaolin with 21.25 ml leachate 2 were the best adsorbents for PbCl2 and CdCl2. The capture efficiencies of PbCl2 and CdCl2 can reach 95% and 63.88%, with the increase of 36% and 53%, respectively. Using leachate as modifying agent had the same effect as directly using Na+. Adsorptions of PbCl2 and CdCl2 were still mainly chemical adsorptions. After adsorption of PbCl2, the modified kaolin not only generated PbA12Si2O8, but also produced other chemical compounds. The adsorption of CdCl2 by modified kaolin did not generate CdAl2Si2O8, but other chemical reactions occurred to generate CdAl2O4 and Pb8Cd (Si2O7)3.

Co-capture of PbCl2 and CdCl2 vapors in a high-temperature furnace by green-produced calcium carbonate/montmorillonite composite sorbent

Injecting sorbent into the furnace is a promising technology for heavy metal emission control, and the development of high-performance in-furnace sorbents is of great importance. In this work, the thermal interaction behavior of calcium carbonate/montmorillonite (CM) composite sorbents at high temperatures and the adsorption of heavy metal chloride vapors were investigated. The adsorption performance of the green-produced calcium carbonate/montmorillonite composite sorbent for PbCl2 and CdCl2 vapors was investigated in a self-designed gas-solid two-phase rapid adsorption experimental system. The composite sorbent exhibited better adsorption performance for heavy metal chloride vapors than the single mineral sorbent. When the doping mass ratio of calcium carbonate was 30%, it exhibited superior heavy metal chloride vapor adsorption capacity at 700 ℃ and 800 ℃. The increase of adsorption temperature was beneficial to improved stability of heavy metal elements in the adsorption products. The addition of O2 promoted the adsorption of Pb and Cd by the sorbent, while the presence of CO2, SO2 and NO inhibited the adsorption of Pb and Cd. The characterization results indicated that the calcia-silica-alumina component of the CM composite sorbent underwent a series of thermal interactions at high temperatures. The presence of calcium changed the mineral evolution of the silica-alumina component, produced more active components, and promoted the high-temperature melting of the sorbent. In addition, the excellent pore properties of the CM composite at high temperatures facilitated the rapid diffusion of heavy metal chloride vapor, which also promoted the adsorption of heavy metals.

Migration, solidification/stabilization mechanism of heavy metal in lightweight ceramisite from co-sintering fly ash and electrolytic manganese residue

Municipal solid waste incineration (MSWI) fly ash and electrolytic manganese residue, as hazardous waste, were roasted into lightweight ceramisite with coal fly ash. The migration, transformation and stabilization/solidification mechanism of heavy metals during ceramisite formation process was explored. Heavy metals in ceramisite pellet were concentrated and experienced the transportation among solids below 710 ℃, then heavy metals were prone to flue gas in the form of chlorides above 710 ℃, in particular for Pb, Cd and Cu. Heavy metal chlorides depended on the generation of HCl and Cl2, which needs co-existence of silicon oxide and aluminum oxide. Note that gibbs free energy change of copper chlorides generation reaction decreased with temperature, resulting in higher volatilization rate compared with Mn, Zn and Cr. Remained heavy metals in the solid phase like Cu, Zn and Cr were prone to ion-exchange, balance-charge and specific-adsorb with calcium-bearing minerals (Ca(Mg,Al)(Si,Al)2O6 and (Ca,Fe)SiO3) in ceramisite based on mineral analysis and principle component analysis at 1160 ℃.

Synergistic poisoning of KCl and PbCl2 on commercial V2O5-MoO3/TiO2 catalysts for MSW incineration flue gas denitrification

Alkali and heavy metal chlorides cause the deactivation of selective catalytic reduction (SCR) catalysts during municipal solid waste incineration. In this study, the synergistic poisoning of KCl and PbCl2 on commercial V2O5-MoO3/TiO2 SCR catalysts was investigated. Compared with KCl, PbCl2 could combine with Mo components and protect V sites from poisoning. Besides, the chemical bonds between PbCl2 and V sites were weaker. Hence, the single poisoning of PbCl2 was weak to the denitrification of SCR catalyst. Whereas, under the co-poisoning of KCl and PbCl2, V-O-Cl structures were formed, which suppressed NH3 activation, thereby causing the deactivation of SCR catalyst.

Low-consumption with efficient capture and characteristics of heavy metals from coal combustion by modified kaolin: Experimental and simulation studies

Heavy metals produced by coal combustion tend to bring environmental pollution. The modified additives were prepared by kaolin to capture heavy metals from coal combustion and analyzed by XRD, XRF, FT-IR, SEM and BET. The experimental results showed that the retention rates of heavy metals were ranked as Cr > Zn > Pb > Cd. The best retention of heavy metals was achieved at 1000 °C, while the retention capacity gradually decreased from 1000 to 1300 °C. The trapping effect of heavy metals in dynamic experiment is better than static experiment at 1300 °C. The general ranking of the adsorption capacity of the additives for the four heavy metals was pseudo boehmite-metakaolin (PBK) > aluminum sulfate impregnated metakaolin (AlSK) > metakaolin (MKA) > original kaolin (OKA). The PBK was the best adsorbent with the greatest retention rates of 77.35 %, 74.68 %, 83.35 % and 80.41 % for Pb, Cd, Cr and Zn, respectively. In addition, PBK showed the most significant improvement in the trapping of four heavy metals, with an average improvement of 37.79 % compared to no additives. The geometry models of heavy metal compounds and adsorbents were optimized. The heavy metal oxides were more stable than the chlorides and were more easily adsorbed. There is competitive adsorption between oxides and chlorides of heavy metals. The Al-O-Si-H and Al-O-Si are the best adsorption surfaces for OKA and MKA, respectively. However, CdO and CdCl2 are hardly adsorbed on the Si-O surface of OKA. The frontline orbitals of four heavy metal oxides/chlorides, θ-Al2O3 and α-Al2O3 have been simulated. Computer simulations show that the mechanism of heavy metal oxide/chloride adsorption on additives is a stronger electron transfer induced interaction between the highest occupied molecular orbital of the adsorbate and the lower unoccupied molecular orbital of the adsorbent, which facilitates the formation of stable chemical bonds.

Physico-chemical profile and corrosion mechanism of the failure grate bar from iron ore sintering process

The grate bars are a critical and easily consumable component of the sintering machine, and the control of their corrosion is of great importance to reduce their consumption. This investigation focused on revealing the physicochemical profile of the failure sintering grate bar and the potential corrosion mechanism. The results showed that the superficial area of the failure grate bar consisted of the adhesive layer, corrosion layer, and metal layer from outside to inside. The adhesion layer is characterised by a loose structure, consisting of higher contents of alkali chloride salts and sulphate, which were the typical corrosive substances. The main components of the corrosion layer were Fe2O3 and Cr2O3; the metal layer structure was dense, which remained the original composition of the grate bar. Based on the characteristics of sintering flue gas, the potential corrosion mechanism was summarised into three main types: (a) high-temperature oxidation, due to the periodic exposure of the grate bars to the high-temperature sintering flue; (b) chlorine corrosion, due to the existence of HCl, alkali (heavy) metal chloride salts (KCl, NaCl, PbCl2) in sintering flue gas, which formed the adhesive layer of grate bars; (c) sulphate corrosion, due to the existence of high SO2 contents and sulphate in the flue gas. The research findings are important to guide the development of grate bar corrosion control technologies.

Cultivation of halotolerant bacteria as a basis of the microbial fertilizer “Biotilia”

The ability of salt-resistant growth-promoting phosphate-solubilizing Priestia megaterium Cp-1 and nitrogen- fixing Rhodococcus jostii CA-6 strains to grow on the medium containing oil hydrocarbons (0.1 %) as the only carbon and energy source in the presence of heavy metal ions (0.1‒5.0 mmol/l) providing the enhanced viability in soil contaminated with hydrocarbons, heavy metal and sodium chloride was investigated. The optimum nutrient medium was selected for the growth and development of halotolerant strains Rh. jostii CA-6 and P. megaterium Ср-1 comprising as a product of sugar refining – molasses as the carbon source in an amount of 30 g/l (Meynell medium). Application of 48h culture of Rh. jostii СA-6 and 24h culture of P. megaterium Ср-1 for inoculation of the nutrient medium grown at the agitation rate of the shaker (180 ± 10) rpm appears to be the most efficient fermentation method. To reach the titer of viable strains at least 1.0·10 9 CFU/ml in submerged culture, the most appropriate procedure envisages the introduction of a seed material in an amount of 5 % of nutrient medium volume. Separately cultured strains P. megaterium Cp-1 and Rh. jostii CA-6 – the basic components of the microbial fertilizer “Biotilia” are mixed in the 1:1 ratio and preserve their vital characteristics at an elevated eco-significant level ((1.67‒2.2)·10 9 CFU/ml) in 3 months of storage in the temperature range of +4– +15 °C.

Experimental and Mechanistic Study of Synergistic Removal of Hg by Evaporation from Desulfurization Wastewater

The flue evaporation of desulfurization wastewater can solve the problem that it is difficult to remove some heavy metal ions and chloride ions by conventional methods. A large amount of chloride ions in desulfurization wastewater can also promote the catalytic oxidation removal of Hg in the flue gas. The migration character of chloride ions in the flue evaporation process of desulfurization wastewater was studied by using the coal-fired thermal state experimental platform. The concentrations of Hg0 and Hg2+ in the flue gas at the inlet and outlet of selective catalytic reduction denitration (SCR), electrostatic precipitator (ESP), and wet desulfurization (WFGD) devices were tested, and the synergistic removal of traditional pollutant removal equipment by flue evaporation of desulfurization wastewater was analyzed. The influence of Hg and the effect of the evaporation of desulfurization wastewater at different positions on the removal of Hg in the flue gas were compared and analyzed, and the catalytic mechanism of Hg on the SCR surface was further revealed. The results show that 10% chloride ions enter the flue gas after the desulfurization wastewater evaporates. The content of chlorine elements and evaporation temperature influence the evaporation of desulfurization wastewater. The mechanism of SCR catalytic oxidation of Hg0 was explored; oxygen atoms have catalytic oxidation effects on Hg0 at different positions in the V2O5 molecule in SCR; and chloride ions can enhance the catalytic oxidation of Hg0 by V2O5. The intermediate product HgCl is generated, which is finally converted into HgCl2. The oxidation efficiency of Hg0 in electrostatic precipitation (ESP) is increased from 3% to 18%, and the removal efficiency of Hg is increased from 5% to 10%. The removal efficiency of Hg2+ in WFGD is basically maintained at approximately 85%. In addition, a small amount of Hg2+ was restored to Hg0 in WFGD. The removal efficiency of Hg0 in the flue gas of evaporative desulfurization wastewater before SCR is 65%, and the removal efficiency of gaseous Hg is 62%. When the evaporative desulfurization wastewater before ESP, the synergistic removal efficiency of Hg0 is 39%, and the gaseous Hg removal efficiency is 39%, and the removal efficiency of Hg is 40%. Evaporation of the desulfurization wastewater before SCR was more conducive to the coordinated removal of Hg by the device.

Synergistic effect of polyvinyl chloride and coal ash on thermal separation of heavy metals from MSWI fly ash through molten salt process.

Municipal solid waste incineration fly ash (FA) contains high contents of salts and high concentrations of heavy metals, which makes FA disposal extremely difficult. However, heavy metal elements could potentially be separated from FA during thermal treatment process to make it possible to be recycled. This work aims to study the volatilization of heavy metals in FA treated by molten salt method. The influence of polyvinyl chloride (PVC) and coal ash (CA) on volatilization of heavy metals was investigated. Within the scope of this study, the highest heavy metal removal rate can be under the condition: the calcium chloride/sodium chloride weight ratio 1:1, the FA/molten salt weight ratio 1:10, treatment temperature 1000°C for 2 hours in reducing atmosphere. The volatilization rates of lead, zinc, copper, chromium and manganese were 86.20, 67.53, 65.24, 50.07 and 39.45%, respectively. On the basis of molten salt treatment, adding PVC could promote the volatilization of heavy metals. The volatilization rate of lead was 96.71%, and the volatilization rates of chromium and manganese were higher than 60% when the content of PVC was 5 wt%. When adding 10 wt% CA and 1 wt% polyvinyl chloride, the volatilization rate of lead could reach 100%. The experiments and thermodynamic calculations showed that silicon dioxide and aluminium oxide in CA and hydrochloric acid decomposed from PVC could promote the chlorination and volatilization of heavy metals. The volatilized heavy metal chlorides provided the possibility of recovery and utilization of heavy metals in FA.

Exploration of novel high-temperature heavy metals adsorbent for sludge incineration process: Experiments and theoretical calculations

Adsorption is an effective and environment-friendly method to control the pollution of volatile and semi-volatile heavy metals (HMs) produced during municipal sludge incineration. In this study, the effect of a novel high-temperature adsorbent (attapulgite) on the migration and transformation mechanisms of HMs (Cr, Cu, Zn, Ni, and Pb) was investigated and compared with the conventional adsorbent (kaolin). The results of experiments and characterization showed attapulgite possessed improved adsorption effects than kaolin due to the smaller crystal distortion and more active sites reserved at 850 ℃. Furthermore, it was found that volatile HMs (Pb, and Zn) tend to be retained in the fly ash, while low-volatile HMs were adsorbed in the bottom slag by Si-Al-based absorbents. Meanwhile, the analytical results of BCR and TCLP tests showed that the proportion of unstable fraction of HMs in the adsorption products of attapulgite was much lower than that of raw dry sludge, and exhibited better leaching stability than kaolin. Theoretical calculations revealed that the adsorption of typical heavy metal forms at high temperatures by attapulgite exhibited a tight chemical adsorption, furthermore, the heavy metal oxides were more susceptible to removal by attapulgite (1 1 0) surface than the corresponding heavy metal chlorides. This work demonstrated the effectiveness of attapulgite in controlling heavy metals in furnaces and provided a new perspective on the development of this field.

Degree‐Based Entropy for a Non‐Kekulean Benzenoid Graph

Tessellations of kekulenes and cycloarenes have a lot of potential as nanomolecular belts for trapping and transporting heavy metal ions and chloride ions because they have the best electronic properties and pore sizes. The aromaticity, superaromaticity, chirality, and novel electrical and magnetic properties of a class of cycloarenes known as kekulenes have been the subject of several experimental and theoretical studies. Through topological computations of superaromatic structures with pores, we investigate the entropies and topological characterization of different tessellations of kekulenes. Using topological indices, the biological activity of the underlying structure is linked to its physical properties in (QSPR/QSAR) research. There is a wide range of topological indices accessible, including degree‐based indices, which are used in this work. With the total π‐electron energy, these indices have a lot of iteration. In addition, we use graph entropies to determine the structural information of a non‐Kekulean benzenoid graph. In this article, we study the crystal structure of non‐Kekulean benzenoid graph and then calculate some entropies by using the degree‐based topological indices. We also investigate the relationship between degree‐based topological indices and degree‐based entropies. This relationship is very helpful for chemist to study the physicochemical characterization of non‐Kekulean benzenoid chemical. These numerical values correlate with structural facts and chemical reactivity, biological activities, and physical properties.

Topological Characterization and Graph Entropies of Tessellations of Kekulene Structures: Existence of Isentropic Structures and Applications to Thermochemistry, Nuclear Magnetic Resonance, and Electron Spin Resonance.

Tessellations of kekulenes and cycloarenes are of considerable interest as nanomolecular belts in trapping and transportation of heavy metal ions and chloride ions, as they possess optimal electronic features and pore sizes. A class of cycloarenes called kekulenes have been the focus of several experimental and theoretical studies from the stand point of aromaticity, superaromaticity, chirality, and novel electrical and magnetic properties. In the present study, we investigate the entropies and topological characterization of different tessellations of kekulenes through topological computations of superaromatic structures with pores. We introduce the self-powered vertex degree-based topological indices and then derive the graph entropy measures for three different tessellations (zigzag, armchair, and rectangular) via various molecular descriptors that we derive here. Several applications to computing the molecular properties are pointed out. We demonstrate the existence of isentropic and yet nonisomorphic tessellations of kekulenes for the first time. The two tessellations are predicted to be quite close in energy with comparable energy gaps. Graph theory-based PPP methods with parameters derived from higher levels of theory are proposed to be promising tools for the predictions of relative stabilities of kekulene tessellations. We show that the developed techniques can be applied in the general context of artificial intelligence for the machine generation of nuclear magnetic resonance and electron spin resonance spectroscopic patterns as well as in robust computations of thermochemistry of a large combinatorial libraries of tessellations of kekulenes through the generation of bond-equivalence classes.

Diatomic molecules’ enigmatic constancy as the product of their dissociation energy and interatomic distance

ABSTRACT In this contribution, we show that the product dissociation energy (D) × interatomic distance (R) with regards to a straightforward taxonomy of diatomic molecules comes to assume a relatively high and virtually constant value. It is so much so that the heavier the diatomic molecules at hand, the closer DxR approaches e 2 (where e is the elementary charge intensity in esu). This occurrence is studied herein separately under families arranged from chemically-alike diatomic molecules. Each family (such as the set made of ‘pairs of strictly alkali atoms’, or ‘pairs of strictly halogen atoms’, or ‘pairs of alkali-halogen atoms’, etc), is thus composed of diatomic molecules formed of atoms bearing similar electronic configurations; whereby we initially ended up dealing with 18 families in total. In addition to those, we brought together 10 more families of diatomic molecules each composed of heavy metal atoms belonging respectively to each of the ten columns drawn from the three rows of heavy metals under the Periodic Table, and observed an even better conformance. [Sc2, Y2, La2] is the first family in question; [Ti2, Zr2, Hf2] and [Va2, No2, Ta2] are the next two families; [Zn2, Cd2, Hg2] delineates the last family of heavy metal diatomic molecules of concern. Let us stress that each of these sets embodies diatomic molecules made of heavy metal atoms belonging to the given column of the Periodic Table; thus, bearing alike electronic configurations. We further brought together 5 more families made of heavy metal hydrides, oxides, chlorides, and alkalines. We were motivated to undertake the present research in the light of our insight with regards to (i) the general non-opacity character of neutral bodies vis-à-vis electrical field transmission, and thence (ii) the attractional electric property of neutral bodies – which underlines the disclosed constancy where, particularly for diatomic molecules comprising heavy atoms, the increase in DxR happens to get aligned with the increase in atomic weight 1 (A1) × atomic weight 2 (A2).

Interactions of PbCl2 capture and CdCl2 capture by kaolin in the high-temperature PbCl2-CdCl2-Kaolin reaction system

Using kaolin for capturing hazardous metals is an effective and promising technology. However, interactions of multiple-metals with kaolin are not been clearly understood. Interactions of PbCl2 capture and CdCl2 capture by kaolin in high-temperature PbCl2-CdCl2-Kaolin reaction system were investigated in a two-stage fixed bed at 800 °C. Capture efficiency considering kaolin dihydroxylation and Pb/Al or Cd/Al were used to evaluate capture performance of kaolin. The results showed that kaolin captured more PbCl2 or CdCl2 in the cases that kaolin captured PbCl2 and CdCl2 at the same time, kaolin captured CdCl2 after its first capture of PbCl2 and kaolin captured PbCl2 after its first capture of CdCl2 than in the case that kaolin only captured PbCl2 or kaolin only captured CdCl2. PbCl2 vapor promoted absorption of kaolin for CdCl2, and CdCl2 vapor also promoted adsorption of kaolin for PbCl2. Heavy metal capture effects were controlled by chemical kinetics due to small particle size of kaolin and short contract time between heavy metal chloride and kaolin. PbCl2 vapor or adsorption products on kaolin surface promoted capture effect of CdCl2 through inhibiting desorption rate of CdCl2. Adsorption products promoted eutectic melting of kaolin surface, and slightly melted kaolin surface exposed new layers with more active sites to continue reactions of kaolin with PbCl2 and CdCl2. Therefore, PbCl2 vapor in the gas flow promoted absorption of kaolin for CdCl2, and CdCl2 vapor also promoted adsorption of kaolin for PbCl2. The results can provide an important reference for Pb and Cd capture during MSW incineration.