Ahmed Barhoum

Effect of Cationic and Anionic Surfactants on the Application of Calcium Carbonate Nanoparticles in Paper Coating

Modification of calcium carbonate particles with surfactant significantly improves the properties of the calcium carbonate coating on paper. In this study, unmodified and CTAB (hexadecyltetramethylammonium bromide)- and oleate-modified calcium carbonate nanoparticles were prepared using the wet carbonation technique for paper coating. CTAB (cationic surfactant) and sodium oleate (anionic surfactant) were used to modify the size, morphology, and surface properties of the precipitated nanoparticles. The obtained particles were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, zeta potential measurements, thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM). Coating colors were formulated from the prepared unmodified and modified calcium carbonates and examined by creating a thin coating layer on reference paper. The effect of calcium carbonate particle size and surface modification on paper properties, such as coating thickness, coating weight, surface roughness, air permeability, brightness, whiteness, opacity, and hydrophobicity, were investigated and compared with commercial ground (GCC) calcium carbonate-coated papers. The results show that the obtained calcium carbonate nanoparticles are in the calcite phase. The morphology of the prepared calcium carbonate nanoparticles is rhombohedral, and the average particle diameter is less than 100 nm. Compared to commercial GCC, the use of unmodified and CTAB- and oleate-modified calcium carbonate nanoparticles in paper coating improves the properties of paper. The highest measured paper properties were observed for paper coated with oleate-modifed nanoparticles, where an increase in smoothness (decrease in paper roughness) (+23%), brightness (+1.3%), whiteness (+2.8%), and opacity (+2.3%) and a decrease in air permeability (-26%) was obtained with 25% less coat weight. The water contact angle at a drop age time of 10 min was about 112° for the paper coated with oleate-modified nanoparticles and 42° for paper coated with CTAB-modified nanoparticles compared to 104° for GCC-coated paper.

Roles of in situ surface modification in controlling the growth and crystallization of CaCO3 nanoparticles, and their dispersion in polymeric materials

The in situ surface modification of inorganic nanoparticles (NPs) and its influence on the size, morphology, and particle surface properties is increasingly receiving attention. Control of the size and morphology and perfect dispersion of inorganic NPs in polymer matrices fabricates soft materials with unique optical, electrical, magnetic, gas barrier, self-healing, and thermal and mechanical properties. This study explores the strategy of the in situ modification of inorganic NPs (CaCO3) with cationic and anionic surfactants and the role of in situ modification on the dispersion of these NPs in thermoplastic polymers (poly ε-caprolactone, PCL). The surfactants having an appropriate polar head with a high charge density bind onto the crystal’s nuclei, protect them against extensive aggregation, and consequently control the size, morphology, and surface properties of the produced NPs. This permits formulation of hybrid materials with enhanced thermal stability and tensile modulus and with a marked increase of the crystallization rate.

Seed-Mediated Hot-Injection Synthesis of Tiny Ag Nanocrystals on Nanoscale Solid Supports and Reaction Mechanism

Controlling the size and shape of noble Ag nanocrystals (NCs) is of great interest because of their unique size- and shape-dependent properties, especially below 20 nm, and because of interesting applications in drug delivery, sensing, and catalysis. However, the high surface energy and tendency of these tiny NCs to aggregate deteriorates their unique properties and limits their applications. To avoid the aggregation of Ag NCs and improve their performance, we report a seed-mediated hot injection approach to synthesize highly dispersed tiny Ag NCs on a nanosized solid CaCO3 support. This simple, low-cost, and effective chemical approach allows for synthesizing highly uniform Ag NCs (∼10 nm) on the surface of presynthesized CaCO3 single NCs (∼52 nm) without any aggregation of the Ag NCs. Viscose fibers were coated with the Ag@CaCO3 composite nanoparticles (NPs) produced, as well as with ∼126 nm Ag NPs for reference. The Ag@CaCO3 composite NPs show excellent UV protection and antibacterial activity against Escherichia coli. In addition, they give a satin sheen gold to a dark gold color to the viscose fibers, while the Ag NPs (∼126 nm) result in a silver color. The proposed synthesis approach is highly versatile and applicable for many other noble metals, like Au or Pt.

Review: nanoparticles and nanostructured materials in papermaking

The introduction of nanoparticles (NPs) and nanostructured materials (NSMs) in papermaking originally emerged from the perspective of improving processing operations and reducing material consumption. However, a very broad range of nanomaterials (NMs) can be incorporated into the paper structure and allows creating paper products with novel properties. This review is of interdisciplinary nature, addressing the emerging area of nanotechnology in papermaking focusing on resources, chemical synthesis and processing, colloidal properties, and deposition methods. An overview of different NMs used in papermaking together with their intrinsic properties and a link to possible applications is presented from a chemical point of view. After a brief introduction on NMs classification and papermaking, their role as additives or pigments in the paper structure is described. The different compositions and morphologies of NMs and NSMs are included, based on wood components, inorganic, organic, carbon-based, and composite NPs. In a first approach, nanopaper substrates are made from fibrillary NPs, including cellulose-based or carbon-based NMs. In a second approach, the NPs can be added to a regular wood pulp as nanofillers or used in coating compositions as nanopigments. The most important processing steps for NMs in papermaking are illustrated including the internal filling of fiber lumen, LbL deposition or fiber wall modification, with important advances in the field on the in situ deposition of NPs on the paper fibers. Usually, the manufacture of products with advanced functionality is associated with complex processes and hazardous materials. A key to success is in understanding how the NMs, cellulose matrix, functional additives, and processes all interact to provide the intended paper functionality while reducing materials waste and keeping the processes simple and energy efficient.

Preparation and characterization of ultra-hydrophobic calcium carbonate nanoparticles

Anionic surfactants based on fatty acids are usually used to modify the particle surface properties of CaCO3 with the aim to enhance its dispersion and compatibility with polymer matrices. In this study sodium oleate was used for the preparation of ultrahydrophobic CaCO3 nanoparticles using a wet carbonation route. The effect of sodium oleate on the characteristics, particle size, morphology, surface potential, thermal decomposition and hydrophobicity of CaCO3, was investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), Zeta potential, thermogravimetric analysis (TGA) and water contact angle measurement (WCA). The results showed that the addition of 2 wt% sodium oleate helps in reducing the particle size from 2 μm length scalenohedral particles to 45 nm rhombohedral particles and modifying of the hydrophobic property of CaCO3.

Review on nanoparticles and nanostructured materials: history, sources, toxicity and regulations

Nanomaterials (NMs) have gained prominence in technological advancements due to their tunable physical, chemical and biological properties with enhanced performance over their bulk counterparts. NMs are categorized depending on their size, composition, shape, and origin. The ability to predict the unique properties of NMs increases the value of each classification. Due to increased growth of production of NMs and their industrial applications, issues relating to toxicity are inevitable. The aim of this review is to compare synthetic (engineered) and naturally occurring nanoparticles (NPs) and nanostructured materials (NSMs) to identify their nanoscale properties and to define the specific knowledge gaps related to the risk assessment of NPs and NSMs in the environment. The review presents an overview of the history and classifications of NMs and gives an overview of the various sources of NPs and NSMs, from natural to synthetic, and their toxic effects towards mammalian cells and tissue. Additionally, the types of toxic reactions associated with NPs and NSMs and the regulations implemented by different countries to reduce the associated risks are also discussed.

Molecularly imprinted polymers based biomimetic sensors for mosapride citrate detection in biological fluids

Computational modeling was applied to study the intermolecular interactions in the pre-polymerization mixture and find a suitable functional monomer to use in the design of a new molecularly imprinted polymer (MIP) for mosapride citrate which is considerably a large molecule (as the citrate ion is also included in calculations as it has centers that can take part in interaction with monomer via hydrogen bonding). Based on these calculations, methacyrlic acid (MAA) was selected as a suitable functional monomer. Mosapride citrate selective MIP and a non-imprinted polymer (NIP) were synthesized and characterized using FTIR, TGA and SEM and then incorporated in carbon paste electrodes (CPEs). The designed modified sensor revealed linear responses in the ranges of 1×10-4-8×10-7 and 8×10-7-8×10-8molL-1 with a limit of detection (LOD) of 2.6×10-8molL-1. The results of the sensor exhibited high selectivity over interfering species and could be applied for the determination of mosapride citrate in pure solutions, pharmaceutical preparations, urine and human serum samples.

PVC membrane, coated-wire, and carbon-paste ion-selective electrodes for potentiometric determination of galantamine hydrobromide in physiological fluids

We report on highly-sensitive ion-selective electrodes (ISEs) for potentiometric determining of galantamine hydrobromide (GB) in physiological fluids. Galantamine hydrobromide (GB) was selected for this study due to its previous medical importance for treating Alzheimers disease. Three different types of ISEs were investigated: PVC membrane electrode (PVCE), carbon-paste electrode (CPE), and coated-wire electrode (CWE). In the construction of these electrodes, galantaminium-reineckate (GR) ion-pair was used as a sensing species for GB in solutions. The modified carbon-paste electrode (MCPE) was prepared using graphene oxide (MCPE-GO) and sodium tetrakis (trifluoromethyl) phenyl borate (MCPE-STFPB) as ion-exchanger. The potentiometric modified CPEs (MCPE-GO and MCPE-STFPB) show an improved performance in term of Nernstian slope, selectivity, response time, and response stability compared to the unmodified CPE. The prepared electrodes PVCE, CWE, CPE, MCPE-GO and MCPE-STFPB show Nernstian slopes of 59.9, 59.5, 58.1, 58.3 and 57.0 mV/conc. decade, and detection limits of 5.0 × 10-6, 6.3 × 10-6, 8.0 × 10-6, 6.0 × 10-6 and 8.0 × 10-6 mol L-1, respectively. The prepared ISEs also show high selectivity against cations (i.e. Na+, K+, NH4+, Ca2+, Al3+, Fe3+), amino acids (i.e. glycine, L-alanine alanine), and sugars (i.e. fructose, glucose, maltose, lactose). The prepared ISEs are applicable for determining GB in spiked serums, urines, and pharmaceutical preparations, using a standard addition and a direct potentiometric method. The fast response time (<10 s), long lifetime (1-5 weeks), reversibility and stability of the measured signals facilitate the application of these sensors for routine analysis of the real samples.

Engineered nanomaterials for wastewater treatment: current and future trends

Abstract The rapidly increasing population, depleting water resources, and climate change resulting in prolonged droughts and floods have rendered drinking water as a competitive resource in many parts of the world. Therefore, any form of water, reuse or recycle will help to mitigate this challenge. Conversely, municipal, industrial, and natural activities produce large quantities of liquid wastes and effluents which pose severe threats to the environment and human health. There are several conventional physical, chemical, and biological technologies for the removal of pollutants from wastewater. However, these conventional technologies focus only on the primary wastewater treatment, especially on the physical separation of solid particles and release high concentration of toxic phosphorus, nitrogen, and other ionic compounds into the environment. Thus, latest technology involving nanotechnology is highly potent in advancing wastewater treatment via nanomaterials and nanosorbents. These nanomaterials have been established in the development of separation membranes, catalytic, and adsorbent materials to enhance the removal of specific components of wastewater and improve productivity. This chapter addresses recent developments in wastewater treatment using nanotechnology, and the implications associated with applications in developing countries, looking at the use of nanotechnology in groundwater treatment and water purification as a basis to develop treatment systems adaptable for wastewater. In addition, future directions of nanomaterials in water treatment applications, their limitations, and legal frameworks were also discussed.

Biological synthesis of nanoparticles: an environmentally benign approach

Abstract Scientists are expanding their interests toward synthesizing metal and metal oxide nanoparticles, as they provide unique physical, chemical, and biological properties. Conventional physical and chemical methods for synthesis of metal and metal oxide nanoparticles become accountable for various biological risks due to their general toxicity and negative impact on the environment. The plant extract is an alternative green technology used for the production of metal and metal oxide nanoparticles. Biomolecules present in plant extracts can be used to reduce metal ions to nanoparticles through a single-step green synthesis process. The present chapter discusses current trends in the plants extract and microorganism biosynthesis of various types of metallic and metal oxide nanoparticles and highlights the potential applications of fabricated nanoparticles. The influence of the reaction condition, such as temperature, pH, concentration of extracts, concentration of the metal salt solution, mixing ratio, and incubation time, are discussed.