China
Africa
Explore chapters and articles related to this topic
Amphiphilic Systems as Biomaterials Based on Chitin, Chitosan, and Their Derivatives
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
The incorporation of PPDO into chitosan would lead to the controllability of physical properties by controlling the chemical structure of the graft copolymer. Similar architecture was obtained by grafting ɛ-caprolactone (ɛ-CL) oligomers onto the hydroxyl groups of chitosan via ring-opening polymerization.69 In this reaction, methanesulfonic acid plays a dual solvent and catalyst role in the graft polymerization process. Due to protective protonation of amine group of chitosan in acidic medium, grafting of ɛ-CL takes place mainly on hydroxyl groups of chitosan. The resultant chitosan-g-PCL showed improved solubility in a variety of organic solvents, and easy to be processed into nanofibers via electrospinning. Owing to the negative membrane potential of cells, it was promising that these amino-reserved chitosan-g-PCL copolymer fibers could generate a cationic surface to promote cell adhesion when used as tissue engineering scaffolds. Radiochemical techniques have recently caught the attention of researchers as an alternate process. Yu et al.70 used γ-irradiation for grafting butylacrylate. They observed that grafting efficiency increases when the monomer concentration and total dose increase or when chitosan concentration and reaction temperature decrease. Compared with chitosan films, chitosans grafted with butylacrylate show larger hydrophobicity and best mechanical strength. Singh et al.71 have grafted poly(acrylonitrile) onto chitosan using a microwave irradiation technique under homogeneous conditions. They obtained 70% efficiency within 90 s.
A Comparative Kinetic Study of Chalcopyrite Leaching Using Alternative Oxidants in Methanesulfonic Acid System
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Junmo Ahn, Jiajia Wu, Jaeheon Lee
Methanesulfonic acid (MSA) is one of the alternative lixiviants which can replace sulfuric acid in a certain condition. MSA is originally developed as an anti-scalant (Bell 1998; Sangeeta and MacDonald 1999). It has characteristics of high metals solubility with low corrosiveness and toxicity (Gernon 1999). There are several studies using MSA for copper leaching. A chalcopyrite concentrate leaching study was carried out with 0.5 M MSA and 3.0 M ferric chloride and achieved 100% copper extraction within 6 hours at 90oC (Hidalgo et al. 2018). Ores associated with chalcopyrite and bornite (Cu5FeS4) were also leached by MSA, and 95% copper extraction was achieved using 0.75 M MSA and 3.0 M ferric chloride within 2 hours at 90oC (Hidalgo et al. 2019). Crane and Sapsford reported an MSA leaching study of mine tailings associated with arsenic sulfide minerals. The copper extraction was 60% within 24 hours using 2.0 M MSA at 21oC (Crane and Sapsford 2018).
Separation of Cobalt, Nickel, and Copper from Synthetic Metallic Alloy by Selective Dissolution with Acid Solutions Containing Oxidizing Agent
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Thanh Tuan Tran, Hyun Seung Moon, Man Seung Lee
Nickel (size: 3–7 μm, Alfa Aesar, 99.9%, Canada), cobalt (size < 44 μm, Alfa Aesar, 99.5%, USA), and copper (granular, Junsei Chemical Co., 99.5%, Japan) were employed for the leaching experiments. Oxidizing reagents such as hydrogen peroxide (H2O2, Daejung Chemical. Co. >30%, Korea), sodium chlorate (NaClO3, Daejung Chemical. Co., Korea), and sodium hypochlorite (NaClO, Sigma-Aldrich Co., with available chlorine 10–15%, USA) were used without any purification. The acidity of the solutions was adjusted by diluting appropriate amount of concentrated acids like sulfuric acid (H2SO4, Daejung Co., >95%, Korea), hydrochloric acid (HCl, Daejung Co., 35%, Korea), methanesulfonic acid (CH3SO3H, Daejung Co., >99.0%, Korea), and acetic acid (CH3COOH, Samchun pure chemical. Co., >99.5%, Korea) with doubly distilled water.
Removing fluoride from hot spring wastewater by an electrolysis system with a perforated plate as a diaphragm
Published in Cogent Engineering, 2020
The ion concentrations of F−, chloride ion (Cl−), nitrate ion (NO3−), sulfide ion (SO42-), sodium ion (Na+), potassium ion (K+), ammonium ion (NH4+), Mg2+, and calcium ion (Ca2+) were analyzed using an ion chromatograph (Cation: Thermo ICS1500, Separation column IonPac CS12A, Eluent Methanesulfonic acid 30 mmol/L, Suppressor CERS 500), (Anion: Thermo ICS2000, Separation column IonPac AS18, Eluent KOH 23–40 mmol/L (gradient), Suppressor AERS 500).