Variability in Quantity and Salinity of Produced Water from an Oil Production in South Kuwait

Produced water (PW) is the largest waste stream in the oil and gas industry. Water remains trapped for millions of years in the reservoir with oil and gas. When a hydrocarbon reservoir is infiltrated by a production well, the produced fluids commonly contain water. The understanding of this water’s constituents and volumes is vital for the sustainable continuity of production operations, as PW has a number of negative impacts on the infrastructure integrity of the operation. On the other hand, PW can be an alternative source of irrigation water as well as of industrial salt. Interestingly, both the quantity as well as the quality of PW do not remain constant but can vary, both progressively and erratically, even over short periods of time. This paper discusses such a situation of variable PW in an oil and gas operation in the State of Kuwait.

Co-Production of High-Grade Dissolving Pulp,Furfural,and Lignin from Eucalyptus via Extremely Low Acid Pretreatment and Pulping Technologies and Catalysis

Hemicellulose and lignin are not reasonably utilized during the dissolved pulp preparation process.This work aimed to propose a process for the co-production of dissolving pulp,furfural,and lignin from eucalyptus.High-grade dissolving pulp was prepared from eucalyptus using a combination of extremely low acid(ELA)pretreatment,Kraft cooking,and elementary chlorine-free(ECF)bleaching.The obtained pre-hydrolysate was catalytic conversion into furfural in a biphasic system,and lignin during Kraft cooking and ECF was recovered.The process condition was discussed as well as the mass flow direction.The results showed that ELA pretreatment could effectively remove 80.1%hemicellulose.Compared with traditional hydrothermal pretreatment,the ELA pretreatment significantly increased the xylose yield from 5.05 to 14.18 g/L at 170℃ for 2 h,which had practical significance for furfural production.The 82.7%furfural yield and 82.9%furfural selectivity were obtained from xylose-rich pre-hydrolysate using NaCl as a phase modifier in a biphasic system with 4-methyl-2-pentanone(MIBK)as an organic phase by ion exchange resin catalysts at 190℃ for 2 h.Subsequently,the pretreated eucalyptus was subjected to Kraft cooking,and the optimal alkali amount was 14%.Then,the Kraft pulp was bleached using the O-D1-EP-D_(2) sequence,and dissolving pulp was obtained with an ISO brightness of 86.0%,viscosity of 463 mL/g,andα-cellulose content of 95.4%.The Kraft lignin which has a potential application was investigated by 2D-HSQC NMR and 31P NMR.The results showed that the S/G ratio of Kraft lignin was 1.93,and the content of phenolic hydroxyl groups was 2.53 mmol/g.Moreover,based on the above proposed process,30.5 g dissolving pulp,5.5 g furfural,and 21.2 g lignin per 100 g eucalyptus chips(oven dry)were produced.This research will provide new catalysis and pulping technical routes for dissolving pulp,furfural,and Kraft lignin products,which are in great demand in the chemical industry.

Formulation, optimization & evaluation of mouth dissolving film of nifedipine by using design of experiment

The oral mucosa is vascularized,drugs can be absorbed directly and can enter the systemic circulation without firstpass metabolism[1].This advantage can be used in preparing products with increased oral bioavailability of molecules that undergo first pass metabolism.Thus oral mucosa is an attractive site for drug delivery[2,3].The objective of this research work is to formulate mouth dissolving film of nifedipine for enhanced bioavailability.nifedipine is used to treat hypertension and angina pectoris.

Development, Application and Prospect of Dissolving Microneedles

In recent years, as a new transdermal drug delivery method, microneedle transdermal drug delivery technology accelerates the absorption of drugs through micron pores, which has been widely used in the field of medicine and cosmetics. Dissolving microneedles have the characteristics of good biocompatibility and fast dissolution speed, which attract more and more researchers’ attention and research. In this paper, the concept, properties and preparation methods of dissolving microneedles as well as the research status of dissolving microneedles in the field of medicine and cosmetics in recent years were summarized and prospected, so as to enable researchers to have a clearer and comprehensive understanding of dissolving microneedles and prospect the application and development prospects of dissolving microneedles in the industry.

Recent progress on nanomaterial-based electrochemical dissolved oxygen sensors

Dissolved oxygen(DO)usually refers to the amount of oxygen dissolved in water.In the environment,medicine,and fermentation industries,the DO level needs to be accurate and capable of online monitoring to guide the precise control of water quality,clinical treatment,and microbial metabolism.Compared with other analytical methods,the electrochemical strategy is superior in its fast response,low cost,high sensitivity,and portable device.However,an electrochemical DO sensor faces a trade-off between sensitivity and long-term stability,which strongly limits its practical applications.To solve this problem,various advanced nanomaterials have been proposed to promote detection performance owing to their excellent electrocatalysis,conductivity,and chemical stability.Therefore,in this review,we focus on the recent progress of advanced nanomaterial-based electrochemical DO sensors.Through the comparison of the working principles on the main analysis techniques toward DO,the advantages of the electrochemical method are discussed.Emphasis is placed on recently developed nanomaterials that exhibit special characteristics,including nanostructures and preparation routes,to benefit DO determination.Specifically,we also introduce some interesting research on the configuration design of the electrode and device,which is rarely introduced.Then,the different requirements of the electrochemical DO sensors in different application fields are included to provide brief guidance on the selection of appropriate nanomaterials.Finally,the main challenges are evaluated to propose future development prospects and detection strategies for nanomaterial-based electrochemical sensors.

Dissolvable temporary barrier:a novel paradigm for flexible hydrogel patterning in organ-on-a-chip models

A combination of hydrogels and microfluidics allows the construction of biomimetic three-dimensional(3D)tissue models in vitro,which are also known as organ-on-a-chipmodels.The hydrogel patterningwith awell-controlled spatial distribution is typically achieved by embedding sophisticated microstructures to act as a boundary.However,these physical barriers inevitably expose cells/tissues to a less physiologically relevant microenvironment than in vivo conditions.Herein,we present a novel dissolvable temporary barrier(DTB)strategy that allows robust and flexible hydrogel patterning with great freedom of design and desirable flow stimuli for cellular hydrogels.The key aspect of this approach is the patterning of a water-soluble rigid barrier as a guiding path for the hydrogel using stencil printing technology,followed by a barrier-free medium perfusion after the dissolution of the DTB.Single and multiple tissue compartments with different geometries can be established using either straight or curved DTB structures.The effectiveness of this strategy is further validated by generating a 3D vascular network through vasculogenesis and angiogenesis using a vascularized microtumor model.As a new proof-of-concept in vasculature-on-a-chip,DTB enables seamless contact between the hydrogel and the culture medium in closed microdevices,which is an improved protocol for the fabrication ofmultiorgan chips.Therefore,we expect it to serve as a promising paradigm for organ-on-a-chip devices for the development of tumor vascularization and drug evaluation in the future preclinical studies.

Straw mulching alters the composition and loss of dissolved organic matter in farmland surface runoff by inhibiting the fragmentation of soil small macroaggregates

Straw mulching is a widespread practice for reducing the soil carbon loss caused by erosion.However,the effects of straw mulching on dissolved organic matter(DOM)runoff loss from black soil are not well studied.How straw mulching affects the composition and loss of runoff DOM by changing soil aggregates remains largely unclear.Here,a straw mulching treatment was compared to a no mulching treatment(as a control)on sloping farmland with black soil erosion in Northeast China.We divided the soil into large macroaggregates(>2 mm),small macroaggregates(0.25-2 mm),and microaggregates(<0.25 mm).After five rain events,the effects of straw mulching on the concentration(characterized by dissolved organic carbon(DoC)and composition(analyzed by fluorescence spectroscopy)of runoff and soil aggregate DOM were studied.The results showed that straw mulching reduced the runoff amount by 54.7%.Therefore,although straw mulching increased the average DOc concentration in runoff,it reduced the total runoff DOM loss by 48.3%.The composition of runoff DOM is similar to that of soil,as both contain humic-like acid and protein-like components.With straw mulching treatment,the protein-like components in small macroaggregates accumulated and the protein-like components in runoff declined with rain events.Fluorescence spectroscopy technology may help in understanding the hydrological paths of rain events by capturing the dynamic changes of runoff and soil DOM characteristics.A variation partitioning analysis(VPA)indicated that the DOM concentration and composition of microaggregates explained 68.2%of the change in runoff DOM from no mulching plots,while the change in runoff DOM from straw mulching plots was dominated by small macroaggregates at a rate of 55.1%.Taken together,our results demonstrated that straw mulching reduces the fragmentation of small macroaggregates and the loss of microaggregates,thus effecting DOM compositions in soil and reducing the DOM loss in runoff.These results provide a theoretical basis for reducing carbon loss in sloping farmland.

Environmental dynamics of nitrogen and phosphorus release from river sediments of arid areas

Human activities lead to the accumulation of a large amount of nitrogen and phosphorus in sediments in rivers.Simultaneously,nitrogen and phosphorus can be affected by environment and re-enter the upper water body,causing secondary pollution of the river water.In this study,laboratory simulation experiments were conducted initially to investigate the release of nitrogen and phosphorus from river sediments in Urumqi City and the surrounding areas in Xinjiang Uygur Autonomous Region of China and determine the factors that influence their release.The results of this study showed significant short-term differences in nitrogen and phosphorus release characteristics from sediments at different sampling points.The proposed secondary kinetics model(i.e.,pseudo-second-order kinetics model)better fitted the release process of sediment nitrogen and phosphorus.The release of nitrogen and phosphorus from sediments is a complex process driven by multiple factors,therefore,we tested the influence of three factors(pH,temperature,and disturbance intensity)on the release of nitrogen and phosphorus from sediments in this study.The most amount of nitrate nitrogen(NO_(3)^(–)-N)was released under neutral conditions,while the most significant release of ammonia nitrogen(NH_(4)^(+)-N)occurred under acidic and alkaline conditions.The release of nitrite nitrogen(NO_(2)^(-)-N)was less affected by pH.The dissolved total phosphorus(DTP)released significantly in the alkaline water environment,while the release of dissolved organic phosphorus(DOP)was more significant in acidic water.The release amount of soluble reactive phosphorus(SRP)increased with an increase in pH.The sediments released nitrogen and phosphorus at higher temperatures,particularly NH_(4)^(+)-N,NO_(3)^(–)-N,and SRP.The highest amount of DOP was released at 15.0℃.An increase in disturbance intensity exacerbated the release of nitrogen and phosphorus from sediments.NH_(4)^(+)-N,DTP,and SRP levels increased linearly with the intensity of disturbance,while NO_(3)^(–)-N and NO_(2)^(–)-N were more stable.This study provides valuable information for protecting and restoring the water environment in arid areas and has significant practical reference value.

A review of physicochemical properties of dissolved organic carbon and its impact over mountain glaciers

Investigating the characteristics and transformation of water-soluble carbonaceous matter in the cryosphere regions is important for understanding biogeochemical process in the earth system.Water-soluble carbonaceous matter is a heterogeneous mixture of organic compounds that is soluble in aquatic environments.Despite its importance,we still lack systematic understanding for dissolved organic carbon(DOC)in several aspects including exact chemical composition and physical interactions with microorganisms,glacier meltwater.This review presents the chemical composition and physical properties of glacier DOC deposited through anthropogenic emission,terrestrial,and biogenic sources.We present the molecular composition of DOC and its effect over snow albedo and associated radiative forcings.Results indicate that DOC in snow/ice is made up of aromatic protein-like species,fulvic acid-like materials,and humic acid-like materials.Light-absorbing impurities in surface snow and glacier ice cause considerable albedo reduction and the associated radiative forcing is definitely positive.Water-soluble carbonaceous matter dominated the carbon transport in the high-altitude glacial area.Owing to prevailing global warming and projected increase in carbon emission,the glacial DOC is expected to release,which will have strong underlying impacts on cryosphere ecosystem.The results of this work have profound implications for better understanding the carbon cycle in high altitude cryosphere regions.A new compilation of globally distributed work is required,including large-scale measurements of glacial DOC over high-altitude cryosphere regions,to overcome and address the scientific challenges to constrain climate impacts of light-absorbing impurities related processes in Earth system and climate models.

Exploration of the Existence Forms and Patterns of Dissolved Oxygen Molecules in Water

The structure of liquid water is primarily composed of three-dimensional networks of water clusters formed by hydrogen bonds,and dis-solved oxygen is one of the most important indicators for assessing water qual-ity.In this work,distilled water with different concentration of dissolved oxygen were prepared,and a clear negative correlation between the size of water clus-ters and dissolved oxygen concentration was observed.Besides,a phenomenon of rapid absorption and release of oxygen at the water interfaces was unveiled,suggesting that oxygen molecules predominantly exist at the interfaces of water clusters.Oxygen molecules can move rapidly through the interfaces among water clusters,allowing dissolved oxygen to quickly reach a saturation level at certain partial pressure of oxygen and temperature.Further exploration into the mechanism by molecular dynamics simulations of oxygen and water clusters found that oxygen molecules can only exist stably at the interfaces among water clusters.A semi-empirical formula relating the average number of water molecules in a cluster(n)to ^(17)O NMR half-peak width(W)was summarized:n=0.1 W+0.85.These findings provide a foundation for exploring the structure and properties of water.

Impacts of Water-Sediment Regulation Scheme on Chromophoric Dissolved Organic Matter in the Lower Yellow River

As a river with more than 3000 reservoirs in its watershed,the Yellow River has been affected by dams not only on the sediment load,but also on the water quality.Water-sediment regulation scheme(WSRS),which has been carried out annually in the Yellow River since 2002,is a typical human activity affecting river water quality.Chromophoric dissolved organic matter(CDOM)in river is susceptible to changes in ecological and environmental conditions as well as human activities.Here,we report variations in dissolved organic carbon concentrations,compositions and sources of CDOM in time series samples in the lower Yellow River during WSRS.In addition,a parallel factor fluorescence analysis(PARAFAC)method is applied to identify different fluorescent components in water samples during WRSR,showing four major components including tryptophan-like component(C1),microbial humic-like component(C2),terrestrial humic-like component(C3)and tyrosine-like component(C4).In general,C1 increased after water regulation,while C2 and C3 increased after sediment regulation,indicating that the water and sediment released by the dam have different effects on CDOM compositions.Under the impacts of the dam,source of CDOM in the lower Yellow River is mainly autochthonous related to microbial activities,and is regulated by the terrestrial input during WSRS period.Sediment resuspension inhibits microbial activities and reduces the production of autochthonous CDOM.Overall,human activities especially WSRS,as exemplified here,significantly alter the quality and quantity of CDOM in the lower Yellow River,affecting CDOM dynamics and biogeochemical processes in the estuarine environment.

Impact of transparent exopolymer particles on the dynamics of dissolved organic carbon in the Amundsen Sea,Antarctica

The Southern Ocean is an important carbon sink pool and plays a critical role in the global carbon cycling.The Amundsen Sea was reported to be highly productive in inshore area in the Southern Ocean.In order to investigate the influence of transparent exopolymer particles(TEP)on the behavior of dissolved organic carbon(DOC)in this region,a comprehensive study was conducted,encompassing both open water areas and highly productive polynyas.It was found that microbial heterotrophic metabolism is the primary process responsible for the production of humic-like fluorescent components in the open ocean.The relationship between apparent oxygen utilization and the two humic-like components can be accurately described by a power-law function,with a conversion rate consistent with that observed globally.The presence of TEP was found to have little impact on this process.Additionally,the study revealed the accumulation of DOC at the sea surface in the Amundsen Sea Polynya,suggesting that TEP may play a critical role in this phenomenon.These findings contribute to a deeper understanding of the dynamics and surface accumulation of DOC in the Amundsen Sea Polynya,and provide valuable insights into the carbon cycle in this region.

Key Physical Factors Affecting Spatial-temporal Variation of Labile Organic Carbon Fractions by Biochar Driven in Mollisols Region of Northeast China

Biochar is widely used to improve soil physical properties and carbon sequestration. However, few studies focuse on the impact of maize stalk biochar on labile organic carbon(LOC) pool and the relationship between physical properties and LOC fractions. A field positioning experiment was performed in Mollisols region of Northeast China to evaluate the influence of maize stalk biochar on the spatial distribution and temporal changes of physical properties and LOC fractions. Maize stalk biochar treatments included C1(1.5 kg·hm^(-2)), C2(3 kg·hm^(-2)), C3(15 kg·hm^(-2)), C4(30 kg·hm^(-2)), and CK(0). The results showed that maize stalk biochar increased soil water contents(SWC) and soil porosity(SP), but reduced bulk density(BD). Maize stalk biochar reduced dissolved organic carbon(DOC) contents in the 0-20 cm soil layer, ranging from 0.25 g·kg^(-1) to 0.31 g·kg^(-1) in harvest period, while increased in the 20-40 cm soil layer. In addition, the application of biochar had a significant impact on the spatial distribution and temporal change of SWC, BD, SP, DOC, hot-water extractable carbon(HWC), acid hydrolyzed organic carbon(AHC Ⅰ, Ⅱ), and readily oxidized organic carbon(ROC). High amounts of maize stalk biochar up-regulated the contents of soil organic carbon SOC, HWC, AHC Ⅰ, AHC Ⅱ, and ROC. In addition, SWC and SP were the key physical factors to affect LOC fractions. In conclusions, maize stalk biochar could improve physical properties, and then influence LOC fractions, and maize stalk biochar could be used as an organic amendment for restoring degraded soils governed by their rates of addition.

Dissolved Organic Matter Features of Three Adjacent Eastern Mediterranean Urbanized Watersheds

Landscape urbanization broadly affects ecosystems in coastal watersheds, but, until now, the influence of nonpoint source urban inputs on dissolved organic matter (DOM) amount, composition, and source is poorly understood. To understand how DOM composition varied with urbanization, fluorescence excitation-emission matrices (EEMs) were determined for urban and non-urban waters from upstream to downstream sites along three adjacent coastal watersheds that flow into the Mediterranean Sea. Two humic DOM fluorescent components (humic-like and fulvic-like peaks) and two proteinic components (tyrosine-like and tryptophane-like peaks) were identified by EEM fluorescence. The results indicated that urbanization had an important influence on DOM concentration and composition, with urban waters having a high degree of DOM variation due to different land uses surrounding each body of water. Urban waters show a higher DOM fluorescence index (FI), the highest fluorescence intensity of protein-like manifested also by BIX values, and a lower value of the humification index (HIX) than non-urban waters which were dominated by allochthonous inputs. In addition, the EEM was compared in dry and wet season where higher DOM amounts and FI appeared in summer due to autochthonous production coming from algae growth compared to allochthonous input from rainfall dominated in wet season. The concentration of DOC increased from upstream to downstream for the three rivers, especially Beirut River. The increase in DOC values was observed in both dry and wet seasons by 39 and 19 times respectively compared to upstream (0.93 - 0.91 mgC/L).

Dynamics of Potable Well Water Quality in Key Mining Chiefdoms in Kono District, Eastern Sierra Leone

Groundwater is increasingly being used due to its universal availability and generally good quality. However, the risk of contamination of groundwater due to various human activities such as mining is equally increasing across the globe. In this study, the physical parameters of potable well waters in the key mining areas in Nimikoro and Tankoro Chiefdoms in Kono District were analyzed for compliance with drinking water quality standard. To do this, both unpurged and purged well water samples were collected once every month for a period of one year. Some of the well water properties like temperature, Total Dissolved Solids (TDS) and Electrical Conductivity (EC) were measured on site and others determined in the laboratory. The data collected from the laboratory analyses were statistically analyzed in MS Excel, SPSS and ArcGIS environments for quality trends in time-space fabric. The results showed that well water quality in the study area generally fell short of drinking water quality standards of Sierra Leone and WHO. There were high temperature and turbidity during the dry season and then high TDS and EC during the rainy season. Temperature and turbidity also significantly influenced well water quality in the study area, much more than TDS and EC. The implications for drinking water of lower quality than the standard could be huge for the local population and therefore needs the attention of stakeholders in the study area and decision makers in the country.

Impacts of Climate Change on Seawater Temperature and Total Dissolved Solids: Challenges and Sustainable Solutions for Reverse Osmosis Desalination in the Arabian Gulf Region

This article examines the influence of seawater temperature and total dissolved solids (TDS) on reverse osmosis (RO) desalination in the Arabian Gulf region, with a focus on the impact of climate change. The study highlights the changes in seawater temperature and TDS levels over the years and discusses their effects on the efficiency and productivity of RO desalination plants. It emphasizes the importance of monitoring TDS levels and controlling seawater temperature to optimize water production. The article also suggests various solutions, including intensive pre-treatment, development of high-performance membranes, exploration of alternative water sources, and regulation of discharges into the Gulf, to ensure sustainable water supply in the face of rising TDS levels and seawater temperature. Further research and comprehensive monitoring are recommended to understand the implications of these findings and develop effective strategies for the management of marine resources in the Arabian Gulf.

Study of Total Dissolved Solids (TDS) Concentrations Factor of SWCC Al-Khobar Plant Seawater Intakes

This study presents a significant contribution to the field of water quality assessment and sustainable water management practices. By evaluating the levels of total dissolved solids (TDS) in seawater intakes within Al-Khobar desalination production system, the study addresses a crucial aspect of water treatment and environmental impact assessment. The findings provide valuable insights into the variations and trends of TDS levels across different phases of the system, highlighting the importance of monitoring and management strategies. The study provided both gravimetric total dissolved solids (TDS) and electrical conductivity (EC) measurements to analyze TDS calculation factor and evaluate measurement accuracy. Results revealed significant variations in TDS levels across the sampling locations, with phase-2 exhibiting higher levels and greater fluctuations. Phase-3 displayed similar trends but with lower TDS levels, while phase-4 showed slightly different behavior with higher average TDS levels. EC measurements demonstrated a strong correlation with TDS, providing a reliable estimation. However, additional methods such as gravimetric analysis should be employed to confirm TDS measurements. The findings contribute to understanding water quality in the Al-Khobar desalination system, aiding in monitoring, management, and decision-making processes for water treatment and environmental impact assessment. The study enhances the credibility of water quality assessments and supports sustainable water management practices.

Characterization of dissolved organic matter fractions from Lake Hongfeng, Southwestern China Plateau

With XAD-series and ion exchange resins, dissolved organic matter （DOM） from Lake Hongfeng in Southwestern China Plateau was isolated into 6 fractions, i.e., humic acid （HA）, fulvic acid （FA）, hydrophobic neutrals （HON）, hydrophilic acids （HIA）, hydrophilic bases （HIB） and hydrophilic neutrals （HIN）. Those fractions were characterized by high performance size exclusion chromatography, fluorescence spectroscopy and UV absorbance. Among the 6 fractions, FA was predominant and accounted for 51% of the total DOM. The weight-average （Mw） and number-averaged （Mn） molecular weight of these fractions ranged from 1688 to 2355 Da and from 1338 to 1928 Da, respectively. A strong correlation was observed between specific UV absorbance at 280 nm, E2/E3 （absorbance at 250 nm to 365 nm）, and the molecular weight for DOM fractions. UV-Vis fulvic-like fluorescence peaks were found in all fractions. Proteinlike fluorescence peaks existed in HON may indicate that microbial activity was severely in Lake Hongfeng. There was a significant relationship between fluorescence intensities and specific UV absorbance at 254 nm for those DOM fractions, suggesting their similar luminescence characteristics. The values of fluorescence index （f450/500） indicated that hydrophobic fractions may derive from terrestrial sources, and the hydrophilic fractions from microbial and terrestrial origins. Those results suggest that there were inter-relationships between molecular weight, fluorescence and absorbance characteristics, and also subtle consistencies between the hydrophilic and hydrophobic properties and the sources for these 6 fractions from Lake Hongfeng.

Numerical Modelling of Dissolving and Driving Exploitation of Potash Salt in the Qarhan Playa——A Coupled Model of Reactive Solute Transport and Chemical Equilibrium in a Multi-component Underground Brine System

Firstly, the macroscopic chemical equilibrium state of a series of chemical reactions between intercrystal brine and its media salt layer （salt deposit） in Qarhan Salt Lake was studied by using the Pitzer theory. The concept of macroscopic solubility product and its relation with accumulated ore dissolving ratio were presented, which are used in the numerical model of dissolving and driving exploitation of potassium salt in Qarhan Salt Lake. And secondly, with a model forming idea of transport model for reacting solutes in the multi-component fresh groundwater system in porous media being a reference, a two-dimensional transport model coupled with a series of chemical reactions in a multi-component brine porous system （salt deposits） was developed by using the Pitzer theory. Meanwhile, the model was applied to model potassium/magnesium transport in Qarhan Salt Lake in order to study the transfer law of solid and liquid phases in the dissolving and driving process and to design the optimal injection/abstraction strategy for dissolving and capturing maximum Potassium/ Magnesium in the mining of salt deposits in Qarhan Salt Lake.

STUDY ON THE MECHANISM OF NYLON 6, 6 DISSOLVING PROCESS USING CaCl_2/MeOH AS THE SOLVENT

A discussion of the mechanism of nylon 6, 6 dissolving process using CaCl_2/MeOH as the sol-vent is presented. The calcium chloride forms a complex compound with nylon 6, 6 by breakingthe hydrogen bonds. The melting point of the CaCl_2 --nylon 6, 6 complex was found to be reducedby 91K relative to the pure nylon 6, 6 polymer. The role of methanol is somewhat similar to acatalyst. The results demonstrate that the complexation of a Lewis acid (CaCl_2) and a Lewis base(nylon 6, 6) can be used to probe intermolecular interactions such as hydrogen bonding in polymers, to modify the polymer properties and mediate its solubility and processing.