Fresh and Hardened Properties of Portland Cement-Slag Concrete Activated Using the By-Product of the Liquid Crystal Display Manufacturing Process

This experimental research investigated the applicability of the liquid crystal display (LCD) by-product of the refining process as a sustainable and alternative alkali activator for ground granulated blast-furnace slag (GGBFS) blended cement concrete. Three levels of binder replacement using the industrial by-product, and four water/binder ratios were considered in order to evaluate the effects of the replacement in fresh and hardened properties of the blended concrete. XRD and TG analyses confirmed that the by-product that contains abundant alkali compounds promotes the reactivity of GGBFS. The test results indicated that the incorporation of the by-product results in delayed setting and degraded workability due to the highly porous nature of the by-product, yet shows rapid early-age strength development of the blended concrete as conventional alkaline activators for GGBFS. These characteristics shed light on a simple yet effective and practical means of reusing the industrial by-product as an alternative alkaline activator.

The Effect of Alkali Roasting Pretreatment on Nickel Extraction from Limonite Ore by Using Dissolved SO2-Air

Extraction of limonite ore using dissolved SO2–air is an alternative hydrometallurgical method for nickel recovery. This process is carried out at atmospheric pressure and is shown to have good selectivity of nickel over iron, but with a low recovery yield. The literature refers to the application of alkali roasting as pretreatment in laterite ore leaching to increase nickel recovery. Thus, this study aims to apply the combination method of alkali roasting and leaching to extract nickel from limonite ore (1.33% Ni, 46.61% Fe) from the Southeast Sulawesi region. Three alkali compounds were included in the study (NaOH, Na2CO3 and Na2SO4). The batch-leaching process was carried out at pH 1 and 3 and temperatures of 55 and 80 °C for 180 min. The leach liquors were sampled at 15, 60, 90 and 120 min, and concentrations of the extracted metals were measured by Atomic Absorption Spectrometry (AAS). A mineralogy characterization of the raw ore and its residue after leaching was undertaken by using X-Ray Diffraction (XRD), while the thermal decomposition behavior of the ore was characterized by Thermogravimetry Analyzer (TGA)/Differential Scanning Calorimetry (DSC). The addition of Na2CO3, Na2SO4 and NaOH in the ore pretreatment increases nickel recovery from 14.80% without alkali roasting to 23.99%, 28.15% and 39.22%, respectively. The optimum extraction condition for nickel recovery is at pH 1 and a temperature of 80 °C. However, the highest Ni/Fe selectivity of 24,947 is obtained at pH 3 and a temperature of 80 °C, preceded by roasting in the absence of alkali. Compared to other hydrometallurgical processes, the process studied in this work exhibits lower recovery, but provides an alternative to extract nickel from low-grade limonite ore.

Ground Granulated Blast-Furnace Slag and its Activation Methods

. The ground granulated slag is a wide spread component of various types of cement and binding substances. Its pozzolanic activity depends on different factors. It is searched out, that there are no minerals able to liquid maturing in the slag under consideration, the slag activity data according to domestic and foreign standards specifies it as low-active, third rate. Altering the chemical composition to a small degree, specific to a definite type of slag, does not alter its functioning much. The same stands for the slag dispersiveness at the high rate of amorphous state – the dispersiveness rise increases slag activity and water demand, and more dispersed slag does not increase the resistibility of matrix samples in high-flow concrete mix. Thus, this type of slag is supposed to be grounded up to BET surface area equal to 250-300 m2/kg, compared to dispersive capacity СEM 1, and the substitution of a part of cement by slag would not have a significant ifluence on mix water demand. With the increase in the slag content within the cementing component the slag effectiveness index increases and reaches its maximum at 70% cement replacement by slag. A large portion of slag can substantially decrease the hydration of lime in the hardened cement paste of the concrete and lessen the solidity of reinforcement corrosion protection in concrete structures. The article deals with different methods of ground granulated blastfurnace slag activation within the mixed cementing substance: Portland-cement CEM1 + GGBFS. The most widely used way of activation – the usage of sodium and potassium alkalies and liquid glass is quite effective, but it demands expensive artificial components, while the alkali compounds forming at hardening of such a cementing component would be soluble.

The Composition and Use Value of Tree Biomass Ash

Wood-based ash landfilling is increasing issue not only in Latvia but in the whole world as more biomass is used for energy production. Utilization of wood burning waste as fertilizer is already used worldwide, but there is lack of information about chemical composition of wood ash obtained from Latvia plants, so the aim of this study was to determine chemical composition and analyse possible utilization options of wood-based ash from Latvia plants. Therefore wood ash samples from 53 companies were collected, sieved and chemical composition of samples was determined. It was concluded that within higher capacity of furnace more coarse fraction of wood ash was observed which is less valuable as fertilizer. Wood ash is good liming material consisting alkali compounds and other biogenic elements but also heavy metals, which are pollutants and could cause environmental problems.

Controlled synthesis and tunable properties of ultrathin silica nanotubes through spontaneous polycondensation on polyamine fibrils

This paper describes a facile approach to a biomimetic rapid fabrication of ultrathin silica nanotubes with a highly uniform diameter of 10 nm and inner hollow of around 3 nm. The synthesis is carried out through a spontaneous polycondensation of alkoxysilane on polyamine crystalline fibrils that were conveniently produced from the neutralization of a solution of protonated linear polyethyleneimine (LPEI–H+) by alkali compounds. A simple mixing the fibrils with alkoxysilane in aqueous solution allowed for the rapid formation of silica to produce LPEI@silica hybrid nanotubes. These 10-nm nanotubes were hierarchically organized in a mat-like morphology with a typical size of 1–2 micrometers. The subsequent removal of organic LPEI via calcination resulted in silica nanotubes that keep this morphology. The morphology, the structure, the pore properties and the formation mechanism of the silica nanotubes were carefully investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller measurements (BET), and X-ray diffraction (XRD). Detailed studies demonstrated that the formation of the nanotubes depends on the molar ratio of [OH]/[CH2CH2NH] during the neutralization as well as on the basicity of the alkali compound and on the concentration of the silica source. The synthesis of silica nanotubes established here could be easily applied to a fabrication on the kilogram scale. Silica nanotubes that were obtained from the calcination of hybrid nanotubes of LPEI@silica in an N2 atmosphere showed a distinct photoluminescence centered at 540 nm with a maximum excitation wavelength of 320 nm. Furthermore, LPEI@silica hybrid nanotubes were applied to create silica–carbon composite nanotubes by alternative adsorption of ionic polymers and subsequent carbonization.