A Review of Hot Gas Cleaning Techniques for Hydrogen Chloride Removal from Biomass-Derived Syngas

Considering the pressing challenges of supply security and climate change, advanced processes to produce electricity and biofuels from biomass have to be developed. Biomass gasification is a very promising technology, but there is a lack of comprehensive reviews, specifically on the technologies for hydrogen chloride hot gas cleanup, which are necessary in order to work at the same temperature and respect the limits of advanced downstream components. In this review, the Cl content of the main biomasses in Europe is given, and data on syngas content and the tolerance of downstream equipment are highlighted. Hot gas cleaning technologies, which have the advantage of improved thermal efficiency are reviewed, analyzing the thermodynamic and primary and secondary methods. This review identifies NaAlO2 and Na2CO3 within 450–550 °C as the most effective sorbents, which are able to reduce the concentration of HCl below 1 ppm. Nevertheless, H2S cannot be simultaneously removed and has to be removed first, because it reduces the HCl adsorption sorbent capacity.

Chloride Accumulation in Aboveground Biomass of Three Macrophytes (Phragmites Australis, Juncus Maritimus, and Typha Latifolia) Depending on Their Growth Stages and Salinity Exposure. Application for Cl- Removal and Phytodesalinization.

Anthropogenic activities can be the source of saline solid wastes that need to be treated to reduce their salt load to meet the purposes of reuse, valorization or storage. In this context, chloride remediation can be achieved using high-salt accumulating plants. However, there is very limited information on the comparative potential of different species in the same environment, and only scarce data concerning their efficiency as a function of growth stage. In order to rationalize these selection criteria, three macrophytes i.e. common reed (Phragmites australis), sea rush (Juncus maritimus) and cattail (Typha latifolia) were cultivated at two growth stages (6-months old and 1-year old) for 65 days in Cl- spiked substrates (from 0 up to 24 ‰ NaCl). The plants’ survival and potential capacity for removal of Cl- from substrates and accumulation in shoots were investigated. For the three studied species, mature and juvenile plants display a high tolerance to salinity. However, mature specimens with higher shoot biomass and Cl- contents are capable of greater chloride removal than juvenile plants. The sole exception is P. australis which displays just the same phytoremediation potential for both mature and juvenile specimens. Moreover, P. australis has the lowest potential when compared with other species, being 1.5 and 3 times lower than for J. maritimus and T. latifolia. When considering the plant growth and the shoot biomass production, chloride removal rates from the substrate point that mature J. maritimus should preferentially be used to design an operational chloride remediation system. The results highlight the relevance of considering the growth stage of plants used for Cl- removal.

Synthesis of a novel porous Ag2O nanomaterial on ion exchange resin and its application for COD determination of high salinity water

This study reports for the first time on the synthesis of novel resin@P-Ag2O material and its application for reducing the chloride effect on COD determination of high salinity water. This engineered core–shell nanomaterial with cationic ion exchange resin core and porous Ag2O shell was prepared by facile ion exchange and silver oxidation method at ambient temperature without using toxic chemicals. The material was characterized by FTIR, XRD, SEM, and SEM–EDX mapping. In the chloride removal test, this material gave a high adsorption capacity of ca. 244 mgCl/gAg at the mild condition with high durability after several adsorption–desorption cycles. Moreover, resin@P-Ag2O was applied for removing chloride in water to improve the accuracy of the SMEWW 5220C:2012 method for COD determination of high salinity water. The result showed that the COD of a water sample with salt content after being treated by the material had a low error (≤ 10%) as compared to the sample without salt. Meanwhile, the COD of salty water measured by the dilution method had an error of around 15%. These results indicate that resin@P-Ag2O material has a very potential application for chloride removal and COD determination of high salinity water.

Chloride Removal of Calcium Aluminate-Layered Double Hydroxide Phases: A Review

Chlorine is a critical element with respect to the use of fossil fuel, recycling of industrial wastes, and water purification. Chlorine could form toxic chemical compounds, corrode pipe systems and boilers, and contaminate surface and ground waters. Calcium aluminate-layered double hydroxides are one of the most promising materials to remove chlorides due to the chemisorption mechanism, since the phases have positively charged interlayers. Many studies on the synthesis and the characterization of calcium aluminate-layered double hydroxides have been extensively conducted, whereas few studies have been conducted on the chloride removal characteristics of the phases. The state-of-the-art studies on the synthesis methods and the structural characteristics of CaAl-LDH phases, the underlying mechanism on the removal of chlorides, and the potential removal rate and the capacity in the present study were thoroughly reviewed.