Recovery Of Bromine Research Articles

Bromine recovery from crude bromine salts by-products of waste printed circuit boards smelting

A green and effective process for bromine recovery from crude bromine salts by-products (CBSBPs) of waste printed circuit boards smelting was developed. Over 99 % of bromine was first converted to Br2(l) under optimal acid oxidation conditions (pH 0, NaClO3 10 g/L, stirring rate 200 rpm, time 30 min). 98.25 % of the as-formed Br2(l) can be then purified and recovered by precisely controlling the extraction (single extraction O/A 1.5, multiple extraction O/A 1/3, extract stages 4, extraction time 3 min, and vibration time 2 min) and stripping (Na2CO3 20.5 g/L, CO(NH2)2 3.15 g/L, stripping A/O 1/3, stripping time 3 min, stripping temperature 55 °C) conditions. The purity of the recovered NaBr exceeds 99 %. Moreover, zero wastewater discharge and the remaining stripping organic phase can be repeatable used over 15 times. The proposed method is a sustainable, green, and closed-loop process for bromine recovery from CBSBPs.

Ipso Substitution of Aromatic Bromine in Chlorinated Waters: Impacts on Trihalomethane Formation.

Parabens and salicylates were examined as disinfection byproduct (DBP) precursors to explore the possible influence of ipso substitution (i.e., halogen exchange) on the yield and speciation of trihalomethanes (THMs) formed during water chlorination. Substoichiometric conversion of C-Br bonds into C-Cl bonds was confirmed for several parabens and salicylates. The co-occurrence of (mono)brominated and nonhalogenated precursors in the presence of free chlorine (but in the absence of added Br-) generated polybrominated THMs, implicating ipso substitution. The THM molar yield, bromine incorporation, and bromine recovery from brominated and nonhalogenated precursor mixtures were commensurate with those observed from equimolar additions of NaBr, indicating efficient displacement of aromatic bromine by free chlorine followed by reincorporation of liberated HOBr into DBP precursors. The THM molar yield from brominated precursors was enhanced by a factor of ≤20 relative to that from nonhalogenated precursors. Trends in THM molar yields and bromine incorporation differed between brominated parabens and brominated salicylates, suggesting that the influence of ipso substitution on THM formation varies with the structure of the organic precursor. Collectively, these results provide new evidence of the often-overlooked role ipso substitution can play in promoting halogen exchange and bromine enrichment among DBPs in chlorinated waters.

Debromination with Bromine Recovery from Pyrolysis of Waste Printed Circuit Boards Offers Economic and Environmental Benefits.

Bromine is an important resource that is widely used in medical, automotive, and electronic industries. Waste electronic products containing brominated flame retardants can cause serious secondary pollution, which is why catalytic cracking, adsorption, fixation, separation, and purification have gained significant attention. However, the bromine resources have not been effectively reutilized. The application of advanced pyrolysis technology could help solve this problem via converting bromine pollution into bromine resources. Coupled debromination and bromide reutilization during pyrolysis is an important field of research in the future. This prospective paper presents new insights in terms of the reorganization of different elements and adjustment of bromine phase transition. Furthermore, we proposed some research directions for efficient and environmentally friendly debromination and reutilization of bromine: 1) precise synergistic pyrolysis should be further explored for efficient debromination, such as using persistent free radicals in biomass, polymer hydrogen supply, and metal catalysis, 2) rematching of Br elements and nonmetal elements (C/H/O) will be a promising direction for synthesizing functionalized adsorption materials, 3) oriented control of the bromide migration path should be further studied to obtain different forms of bromine resources, and 4) advanced pyrolysis equipment should be well developed.

Separation of bromine and hydrocarbons from polymeric constituents in e-waste through thermal treatment with calcium hydroxide

Complete and deep removal of bromine from polymeric constituents in waste printed circuit boards (WPCBs) signifies the prime aim of the commonly deployed catalytic/pyrolytic approach in the treatment of e-waste. To attain this aim, a wide array of debromination agents were utilized with varying degree of effectiveness, scalability, and economic viability. Through the use of a multitude of techniques (flow reactor experiments, chemical analysis, surface characterization, and molecular simulation), this work presents conclusive evidence that co-pyrolysis of tetrabromobisphenol A (TBBA; as a model compound for the bromine content in WPCBs) with calcium hydroxide (Ca(OH)2) results in a complete fixation of the bromine content and produces bromine-free pyrolysis oil. For instance, measurements by IC and FTIR (gas sampling cell) confirms the disappearance of HBr from the gaseous stream during co-pyrolysis of a TBBA (1):Ca(OH)2 (2) mixture between 200 and 500 °C. Likewise, no brominated compounds could be detected from the analysis of the condensate and gas fractions. As the collected oil is dominated by n-alkanes, it is concluded that Ca(OH)2 displays both cracking and debromination capacity. DFT calculations maps out reaction pathways for the transformation of Ca(OH)2 into CaBr2 via the dissociative addition of HBr molecules. Formed CaBr2 could open a venue for a complete recovery of bromine in the thermal treatment of e-waste. Outcomes reported herein shall be instrumental in the design and operation of an effective chemical recycling facility for the ever-increasing loads of e-waste.

Highly efficient recovery of bromine from shale gas wastewater by selective electrochemical oxidation

The recovery of bromine from shale gas wastewater (SGW) by selective electrochemical oxidation is a sustainable way to treat SGW and alleviate the shortage of bromine resources. However, this method suffers from the defect of low extraction efficiency at present. Considering the electrode area is one dominant factor affecting selective bromine extraction performance, the area of the anode was first investigated, and then 1.5 × 6 cm2 was selected as the optimal size for 300 mL wastewater in the Φ6 × 14 cm3 bottle. Through the study on the effect of organics, it was found that methanol (MeOH) had little impact on the electro-oxidation of bromine, while polyacrylamide (PAM) had a serious inhibition on bromine extraction. The adhesion of organics on the electrode surface and the consumption of bromine for the degradation of the organic result in a serious inhibition of bromine extraction. To improve the selective oxidation of bromine yield in real SGW, an advanced oxidation method based on persulfate was used to degrade the organics in SGW, and the yield increased from 25.4% to 77.8% after pretreatment. During this process, the theoretical hydrogen production is 1.01 mmol/L at the cathode in 6 h. The final effluent mixed anode and cathode chambers were neutral, which is environmental friendliness. These results could push the development of shale gas wastewater treatment.

Debromination of tetrabromobisphenol A in aqueous amine solutions under hydrothermal conditions

Tetrabromobisphenol A (TBBPA) powder was subjected to an aqueous amine solution in a small bomb-type batch reactor at temperatures from 447 to 553 K and pressures from 0.79 to 6.4 MPa. The effectiveness of aqueous amine solutions under hydrothermal conditions was examined for debromination of TBBPA, which is a brominated flame retardant commonly contained in printed circuit boards. The amines tested were methylamine, dimethylamine and trimethylamine. Compared to aqueous ammonia and aqueous sodium hydroxide solutions, all the amine solutions tested were more effective. For instance, the 89% debromination of the initial bromine contained in TBBPA was recovered by a 0.6 mol/kg aqueous methylamine solution at 533 K in 20 min. The debromination of TBBPA was accelerated with increasing reaction temperature and amine concentration. The four major products, 2,6-dibromophenol, 2-bromophenol, phenol and 2,6-dibromo-4-(1-methylethenyl)phenol, were detected by GCMS and the three former products were quantified by HPLC. According to the product distributions over time, a primary pathway of TBBPA debromination was proposed, in which the cleavage of a carbon-carbon bond initially took place, followed by debromination. The debromination reaction in an aqueous methylamine solution under hydrothermal conditions was described by pseudo first order reaction kinetics, and the activation energies changed at 473 K, and that above 473 K was much smaller than that in pyrolysis reported in the literature. The debromination rate constants at 473 and 533 K were proportional to methylamine concentration up to 0.3 mol kg−1, and those increased gradually above the temperature. The authors proposed debromination of TBBPA in an aqueous amine solution under hydrothermal conditions as a new debromination method due to relatively fast reaction rates and recovery of bromine as bromide ion.

Membrane extraction performances and simulation of bromine recovery with poly(vinylidene fluoride) hollow fibre membranes

In this work, the extraction performance of poly(vinylidene fluoride) hollow fibre membranes during bromine recovery from aqueous bromine solution was studied. The results showed that feed volume flow, feed solution concentration and temperature were vital for both flux and mass transfer coefficient; however, the stripping volume flow and stripping played a negligible role on both flux and mass transfer coefficient. A mathematical model was developed to predict the bromine recovery behaviour, and the results of this model agreed well with the experimental data.

Recovery of precious metals from scrap printed circuit boards through pyrolysis

Pyrolysis process has many advantages, if integrated in the process of precious metals recovery from scrap printed circuit boards (PCB): the reduction of energy costs during the milling phase, the improvement of dissolution efficiency, the reduction of non-metal residue, low production of dioxins and recovery of bromine. Despite this it is not clear if the process can be sustained burning volatile products (oil and gas). For this reason in the paper pyrolysis tests on samples of central processing units (CPU) and random access memories (RAM) are presented. The pyrolysis of central processing units yielded about 90% of char, 4% of tar and 6% of gas. The pyrolysis of random access memories yielded 82% of char, 9% of tar and 9% of gas. Char energy content was about 4300kJ/kg for random access memories and 2200kJ/kg for central processing units, tar energy content was about 29,000kJ/kg for both, while gas heating value was respectively 20MJ/kg and 18MJ/kg. Burning all the volatiles obtained from pyrolysis of random access memories and central processing units, respectively 4273kJ/kg and 2066kJ/kg of heat can be obtained.

Catalytic Bromine Recovery: An Enabling Technology for Emerging Alkane Functionalization Processes

Making a quick recovery: The widespread implementation of bromination reactions to manufacture value-added products is contingent upon the development of sustainable and cost-effective means to recycle copious amounts of HBr byproduct. We report families of heterogeneous catalysts for the full recovery of Br2 through HBr oxidation that display unprecedented low-temperature activity and stability.

Absorption and disposition of bromate in F344 rats

Bromate (BrO3−) is a ubiquitous by-product of using ozone to disinfect water containing bromide (Br−). The reactivity of BrO3− with biological reductants suggests that its systemic absorption and distribution to target tissues may display non-linear behavior as doses increase. The intent of this study is to determine the extent to which BrO3− is systemically bioavailable via oral exposure and broadly identify its pathways of degradation. In vitro experiments of BrO3− degradation in rat blood indicate a rapid initial degradation immediately upon addition that is >98% complete at concentrations up to 66μM in blood. As initial concentrations are increased, progressively lower fractions are lost prior to the first measurement. Secondary to this initial loss, a slower and predictable first order degradation rate was observed (10%/min). Losses during both phases were accompanied by increases in Br− concentrations indicating that the loss of BrO3− was due to its reduction. In vivo experiments were conducted using doses of BrO3− ranging from 0.077 to 15.3mg/kg, administered intravenously (IV) or orally (gavage) to female F344 rats. The variable nature and uncertain source of background concentrations of BrO3− limited derivation of terminal half-lives, but the initial half-life was approximately 10min for all dose groups. The area under the curve (AUC) and peak concentrations (Ct=5′) were linearly related to IV dose up to 0.77mg/kg; however, disproportionate increases in the AUC and Ct=5′ and a large decrease in the volume of distribution was observed when IV doses of 1.9 and 3.8mg/kg were administered. The average terminal half-life of BrO3− from oral administration was 37min, but this was influenced by background levels of BrO3− at lower doses. With oral doses, the AUC and Cmax increased linearly with dose up to 15.3mgBrO3−/kg. BrO3− appeared to be 19–25% bioavailable without an obvious dose-dependency between 0.077 and 1.9mg/kg. The urinary elimination of BrO3− and Br− was measured from female F344 rats for four days following administration of single doses of 8.1mgKBrO3/kg and for 15 days after a single dose of 5.0mgKBr/kg. BrO3− elimination was detected over the first 12h, but Br− elimination from BrO3− over the first 48h was 18% lower than expected based on that eliminated from an equimolar dose of Br− (15.5±1.6 vs. 18.8±1.2μmol/kg, respectively). The cumulative excretion of Br− from KBr vs. KBrO3 was equivalent 72h after administration. The recovery of unchanged administered BrO3− in the urine ranged between 6.0 and 11.3% (creatinine corrected) on the 27th day of treatment with concentrations of KBrO3 of 15, 60, and 400mg/L of drinking water. The recovery of total urinary bromine as Br−+BrO3− ranged between 61 and 88%. An increase in the fraction of the daily BrO3− dose recovered in the urine was observed at the high dose to both sexes. The deficit in total bromine recovery raises the possibility that some brominated biochemicals may be produced in vivo and more slowly metabolized and eliminated. This was supported by measurements of dose-dependent increases of total organic bromine (TOBr) that was eliminated in the urine. The role these organic by-products play in BrO3−-induced cancer remains to be established.

Comparative environmental analysis of waste brominated plastic thermal treatments

The aim of this research activity is to investigate the environmental impact of different thermal treatments of waste electric and electronic equipment (WEEE), applying a life cycle assessment methodology. Two scenarios were assessed, which both allow the recovery of bromine: (A) the co-combustion of WEEE and green waste in a municipal solid waste combustion plant, and (B) the staged-gasification of WEEE and combustion of produced syngas in gas turbines. Mass and energy balances on the two scenarios were set and the analysis of the life cycle inventory and the life cycle impact assessment were conducted. Two impact assessment methods (Ecoindicator 99 and Impact 2002+) were slightly modified and then used with both scenarios. The results showed that scenario B (staged-gasification) had a potentially smaller environmental impact than scenario A (co-combustion). In particular, the thermal treatment of staged-gasification was more energy efficient than co-combustion, and therefore scenario B performed better than scenario A, mainly in the impact categories of "fossil fuels" and "climate change". Moreover, the results showed that scenario B allows a higher recovery of bromine than scenario A; however, Br recovery leads to environmental benefits for both the scenarios. Finally the study demonstrates that WEEE thermal treatment for energy and matter recovery is an eco-efficient way to dispose of this kind of waste.

Higher hydrocarbons from methane condensation mediated by HBr

Methane condensation to higher hydrocarbons with a single-pass methane conversion of 30% and total carbon selectivity of 90% has been achieved in a system of two-stage serial reactors. Methane reacts with HBr and oxygen in the first catalyst bed at 660 °C to form CH 3Br and CH 2Br 2, while CH 3Br and CH 2Br 2 are converted to higher hydrocarbons in the second catalyst bed at 240 °C. A reusable sorption material MgO/SiO 2 has been identified for the separation of HBr from H 2O and olefins (performed at 200 °C), making the recovery of bromine and the purification of olefins feasible.

Chemical Reaction Engineering Analysis of the Blowout Process for Bromine Manufacture from Seawater

A chemical reaction engineering model has been constructed to describe the extraction and recovery of bromine from a once-through seawater flow. The process uses a closed-loop circulation flow of air. This strips out free bromine from pre-chlorinated seawater in a packed column. Bromine liberated into the gas reacts with injected sulfur dioxide around a circulation loop to form liquid droplets containing product hydrobromic acid captured by mist elimination. Excesses of chlorine and sulfur dioxide compete for bromine and can reduce the recovery efficiency. Pseudo-homogeneous gas-phase kinetics accounts for simultaneous absorption and gas−liquid reaction of liberated bromine, excess chlorine, and injected sulfur dioxide. Re-circulating sulfur dioxide subsequently absorbs and reacts simultaneously with bromine and chlorine stripping. Parameter values are deduced for typical bromine recovery of 70%. The model can be used for optimizing the excesses of chlorine and sulfur dioxide.

Eco-friendly and versatile brominating reagent prepared from a liquid bromine precursor

Facile bromination of various organic substrates has been demonstrated with a 2 : 1 bromide:bromate reagent prepared from the alkaline intermediate of the conventional bromine recovery process. The reagent is acidified in situ to generate HOBr as the reactive species, which effects bromination. Aromatic substrates that have been successfully brominated under ambient conditions without use of any catalyst include phenols, anilines, aromatic ethers and even benzene. Non-aromatic compounds bearing active methylene group were monobrominated selectively with the present reagent and olefinic compounds were converted into the corresponding bromohydrins in moderate yields. By obtaining the present reagent from the liquid bromine precursor, the twin advantages of avoiding liquid bromine and producing the reagent in a cost-effective manner are realised. When coupled with the additional advantage of high bromine atom efficiency, the present protocol becomes attractive all the way from “cradle to grave”.

Novel debromination method for flame-retardant high impact polystyrene (HIPS-Br) by ammonia treatment

Debromination of flame-retardant brominated high impact polystyrene (HIPS-Br) was performed at 450 °C by ammonia treatment. All inorganic and most organic Br compounds were successfully removed and converted to inorganic NH4Br powder, which allows easy bromine recovery. The liquid degradation products are rich in benzene derivatives and can be used as feedstock or fuel.

WEEE recycling: Pyrolysis of fire retardant model polymers

Pyrolysis treatments of model polymers were made with the aim of studying the recycling of wastes from electronic, electric equipment containing brominated flame retardants. Pyrolysis of flame retarded high impact polystyrene and epoxy resins were made both in flow and closed systems. Products of pyrolysis were analysed with FT–IR spectroscopy and GC–MS and the evolution of bromine was followed with a bromine ion specific electrode. The effect of alkali on pyrolysis was also studied demonstrating, as far epoxy resin is concerned, to be effective on decreasing bromine content in oil and volatile products leading to the recovery of bromine from the residue by washing. The alkali treatment was shown to be less effective in styrenic polymers containing brominated flame retardants.

Recuperação de bromo em soluções aquosas residuais

A laboratory procedure was devised to recover bromine from waste alkaline aqueous solutions used in the isotopic determination of N-15. The laboratory apparatus comprises two round bottom flasks (1 and 2 L), a dropping funnel, a gas bubbler, a gas regulator and glass fittings. The waste solution is acidified with sulfuric acid forming molecular bromine that is stripped out by a flow of nitrogen gas bubbled through the solution. This gas is then bubbled through a solution of lithium hydroxide generating lithium bromide and lithium hypobromite. The efficiency of bromine recovery was estimated to be 82±2%. This resulting solution was successfully reused in the isotopic determination of N-15. The procedure can recycle most of the bromine used in the laboratory saving resources and preserving the environment. The procedure can be adapted to recover bromine of other laboratory waste streams.

Low-Waste Process for Preparing Ketopantolactone, with Electrochemical Recovery of Bromine

The process parameters of dehydrogenation of pantolactone with bromine in chloroform and the possibility of bromine recycling by electrolysis of hydrogen bromide formed in the synthesis of ketopantolactone were studied.

Electrolytic membrane recovery of bromine from waste hydrogen bromide streams

AbstractA novel electrochemical process was developed for the recovery of bromine from waste gas‐phase hydrogen bromide streams. It uses a molten‐salt‐saturated membrane to electrolytically decompose hydrogen bromide into its molecular constituents, which are separated into a hydrogen‐enriched waste stream and a pure bromine product stream. Single‐cell studies were carried out in a configuration consisting of two cell housings (vitreous carbon), two gas‐diffusion electrodes (reticulated vitreous carbon or graphite felt), and a molten salt [(Li0.575K0.133Cs0.292)Br] saturated membrane (zirconia). Single‐cell results at 300°C, based on process stream concentrations ranging from 25 to 75% hydrogen bromide at 50 to 300 mL/min, demonstrated current densities exceeding 1 A/cm2 and removals as high as 95%. Water and acetone (as a light organic contaminant) addition to the process feed, as well as exposure to thermal cycling, showed no deleterious effects on cell performance. Preliminary economics indicate this to be a viable process.

Recovery of Bromine from Waste Gas‐Phase Hydrogen Bromide Streams Using an Electrolytic Membrane

An electrochemical cell is used to demonstrate a significant improvement in the recovery of bromine from waste gas‐phase hydrogen bromide (HBr) streams. The continuous process operates at 300°C and utilizes reticulated vitreous carbon gas‐diffusion electrodes, a molten Br electrolyte, and borosilicate glass fiber membrane. HBr is simultaneously electrolytically decomposed and separated into a hydrogen enriched waste stream and pure anhydrous product stream. Simulated industrial waste streams containing HBr, nitrogen, water vapor, and organic compounds have been tested. These results include removals of greater than 90% and current densities approaching 1.0 A/cm2.