Co-pyrolysis of rice straw with industrial wastes: Waste disposal and environmental remediation

To reduce waste volumes and recover valuable products, char was synthesized via co-pyrolysis of rice straw (RS) with spent tires, sulfur wastes, and CO2. The inclusion of wastes and CO2 in pyrolysis of RS was hypothesized to enhance the sorption ability of char for various contaminants, including 2,4-dinitrotoluene (DNT), 2,4-dichlorophenol (DCP), lead, barium, chromate (CrO42−), and selenate (SeO42−). Using a lab-scale electrical furnace, the co-pyrolysis was conducted, and the soprtion capacity of char was evaluated via a series of batch sorption experiments. The maximum sorption capacity of spent tire–RS char for DNT was 16.8 ± 0.2 mg g−1, much higher than that of RS biochar (10.1 ± 0.3 mg g−1) due to increasing carbon content from the spent tires. The sorption of DCP to the spent tire–RS char was also enhanced via hydrophobic sorption to carbon residues, although not to the same degree of DNT due to deprotonation of the DCP. Compared with RS biochar, co-pyrolysis with raw sulfur wastes and CO2 enhanced sorption of lead, barium, and chromate, which can be attributed to increased cation and anion exchange capacities resulting from developments of oxygen or sulfur-containing functional groups. Sorption of selenate was strongly affected by pH. The results suggest that co-pyrolysis of agricultural and industrial wastes and CO2 is a promising option for the final waste disposal and the production of valuable char, which can be selectively customized for various types of contaminants as sorbents.

Thermal Stability of Inorganic Pigments Synthesized from Galvanic Sludge

Pigments used in ceramic glazes have been obtained by chromium ions extraction from galvanic sludge and their precipitation as barium chromate and lead chromate from technological solutions. The chemical composition was determined by XRF method. Complex thermal analysis TG-DSC, XRD and SEM methods have been used for microstructural characterization and thermal treatment behaviour evaluation, in order to establish the compatibility with the ceramic matrix. XRD spectra have highlighted only lead chromate specific interferences in the monoclinic phase and barium chromate in the orthorhombic phase, suggesting an advanced degree of purity. Weight losses of 2.2% for barium chromate and 3.1% for lead chromate have been recorded on the TG curve at 800�C. As a result of thermal treatment, barium chromate has changed its colour from yellow to green.

A Comparative Study on Conversion of Soluble Cr(VI) into Insoluble Cr(VI) and Reduction of Cr(VI) in Contaminated Groundwater at COPR Dump Site

The most common methodology for removal of Cr(VI) in literatures is the combination of reduction and precipitation process. The disadvantages of this method are presence of high total dissolved solids in the treated water and sludge generation. In order to find a new solution, efforts have been focussed to convert Cr(VI) present in the groundwater, into the useful products like zinc chromate and barium chromate under appropriate conditions. The efficiency of these conversions is compared with the efficiency of the reduction and precipitation process adopted in this study, using sodium metabisulphite. These experimental studies were carried out with stimulated water containing 2000 mg/L of Cr(VI) and then extended to Cr(VI) contaminated groundwater with same concentration. The results are compared and validated through batch experiments.

Effect of Different Variables on the Size Distribution of Barium Chromate Nanoparticles

In this study, the synthesis of BaCrO4 nanoparticles is performed by the reaction between Ba(NO3)2 and (NH4)2CrO4 in the presence of surfactant. Different analyses such as X-ray diffraction (XRD), Transmission electron microscopy (TEM), Dynamic light scattering (DLS), and Energy Dispersive X-ray analysis (EDAX) are carried out to identify the features of nanoparticles. The tests are conducted in different concentrations of reactants and surfactants, and at the end, the results are compared. Optimum concentration is also measured and reported to achieve smaller nanoparticles. The results indicate that, in the synthesis of BaCrO4 nanoparticles, the best performance belongs to Sodium Citrate.

Controlled synthesis of barium chromate multi-layered microdiscs and their photocatalytic activity

BaCrO4 microdiscs composed of multi-layered microplates were successfully synthesized by a facile oxalate-assisted precipitation method. Based on time-dependent experiments, a dissolution–recrystallization–self-assembly process has been proposed.