Elemental sulfur reduction to H2S by Tetrahymena thermophila

Improved Formation of Biomethane by Enriched Microorganisms from Different Rank Coal Seams

The influence of enrichment of culturable microorganisms in in situ coal seams on biomethane production potential of other coal seams has been rarely studied. In this study, we enriched culturable microorganisms from three in situ coal seams with three coal ranks and conducted indoor anaerobic biomethane production experiments. Microbial community composition, gene functions, and metabolites in different culture units by 16S rRNA high-throughput sequencing combined with liquid chromatography-mass spectrometry-time-of-flight (LC-MS-TOF). The results showed that biomethane production in the bituminous coal group (BC)cc resulted in the highest methane yield of 243.3 μmol/g, which was 12.3 times higher than that in the control group (CK). Meanwhile, Methanosarcina was the dominant archaeal genus in the three experimental groups (37.42 ± 11.16-52.62 ± 2.10%), while its share in the CK was only 2.91 ± 0.48%. Based on the functional annotation, the relative abundance of functional genes in the three experimental groups was mainly related to the metabolism of nitrogen-containing heterocyclic compounds such as purines and pyrimidines. Metabolite analysis showed that enriched microorganisms promoted the degradation of a total of 778 organic substances in bituminous coal, including 55 significantly different metabolites (e.g., purines and pyrimidines). Based on genomic and metabolomic analyses, this paper reconstructed the heterocyclic compounds degradation coupled methane metabolism pathway and thereby preliminarily elucidated that enriched culturable bacteria from different coal-rank seams could promote the degradation of bituminous coal and intensify biogenic methane yields.

Construction of CdS-Tetrahymena thermophila hybrid system by efficient cadmium adsorption for dye removal under light irradiation

The water pollution caused by heavy metals and dyes emitted by industries has become a worldwide problem. These pollutants are difficult to be biodegraded. Even at low concentrations, they are toxic and at last threaten human health. Herein, while using Tetrahymena thermophila, a single-celled ciliate protozoa, to enrich and remove the heavy metal Cd²⁺ from water, CdS nanoparticle-Tetrahymena thermophila hybrid system (CdS-T. thermophila) for dye pollution remediation under light irradiation was developed. The conditions of Cd²⁺ enrichment and removal by T. thermophila, construction of efficient CdS-T. thermophila, and decolorization of Congo red using CdS-T. thermophila were investigated. In the presence of cysteine ethyl ester, the removal rate of Cd²⁺ by T. thermophila was 94% at low Cd²⁺ concentration of 1 mg L^-1. The adsorption capacity of T. thermophila to Cd²⁺ reached 43 mg g^-1 at Cd²⁺ concentration of 80 mg L^-1. Using 0.1 g L^-1 constructed CdS-T. thermophila, the decolorization rate of 50 mg L^-1 Congo red solution reached 95% in 60 min under light irradiation. This study provides a new insight to effective removing Cd²⁺ from water by T. thermophila to construct the CdS-T. thermophila and using it to remediate dye pollution in the environment.

Sulfur Reduction at Hyperthermoacidophilic Conditions with Mesophilic Anaerobic Sludge as the Inoculum

Sulfur reduction at hyperthermoacidophilic conditions represents a promising opportunity for metal sulfide precipitation from hot acidic metallurgical streams, avoiding costly cooling down. The suitability of mesophilic anaerobic sludges as the inoculum for sulfur-reducing bioreactors operated at high temperature and low pH was explored. We examined sludges from full-scale anaerobic reactors for sulfur-reducing activity at pH 2.0-3.5 and 70 or 80 °C, with H₂ as an electron donor. At pH 3.5 in batch experiments, sulfidogenesis started within 4 days, reaching up to 100-200 mg·L^-1 of dissolved sulfide produced after 19-24 days, depending on the origin of the sludge. Sulfidogenesis resumed after removing H₂S by flushing with nitrogen gas, indicating that sulfide was limiting the conversion. The best performing sludge was used to inoculate a 4 L gas-lift reactor fed with H₂ as the electron donor, CO₂ as the carbon source, and elemental sulfur as the electron acceptor. The reactor was operated in semibatch mode at a pH 3.5 and 80 °C, and stable sulfide production rates of 60-80 mg·L^-1·d^-1 were achieved for a period of 24 days, without formation of methane or acetate. Our results reveal the potential of mesophilic anaerobic sludges as seed material for sulfur-reducing bioprocesses operated at hyperthermoacidophilic conditions. The process needs further optimization of the volumetric sulfide production rate to gain relevance for practice.

A Critical Review on the Properties and Applications of Sulfur-Based Concrete

The incessant demand for concrete is predicted to increase due to the fast construction developments worldwide. This demand requires a huge volume of cement production that could cause an ecological issue such as increasing the rates of CO₂ emissions in the atmosphere. This motivated several scholars to search for various alternatives for cement and one of such alternatives is called sulfur-based concrete. This concrete composite contributes to reduce the amount of cement required to make conventional concrete. Sulfur can be used as a partial-alternate binder to Ordinary Portland Cement (OPC) to produce sulfur-based concrete, which is a composite matrix of construction materials collected mostly from aggregates and sulfur. Sulfur modified concrete outperforms conventional concrete in terms of rapid gain of early strength, low shrinkage, low thermal conductivity, high durability resistance and excellent adhesion. On the basis of mentioned superior characteristics of sulfur-based concrete, it can be applied as a leading construction material for underground utility systems, dams and offshore structures. Therefore, this study reviews the sources, emissions from construction enterprises and compositions of sulfur; describes the production techniques and properties of sulfur; and highlights related literature to generate comprehensive insights into the potential applications of sulfur-based concrete in the construction industry today.