Hydrogen sulfide removal by catalytic oxidative absorption method using rotating packed bed reactor

Evaluation of a hybrid physicochemical/biological technology to remove toxic H2S from air with elemental sulfur recovery

The removal of toxic hydrogen sulfide (H₂S) from the air at pilot-scale with elemental sulfur recovery was evaluated using Fe-EDTA chelate as a single treatment at a pH of about 8.5. This was later combined with a compost biofiltration process for polishing the pre-treated air. Experiments were performed in a unique container system that allowed deploying either Fe-EDTA chelate or Fe-EDTA chelate/biofiltration treatment (hybrid system). The results showed the feasibility of H₂S removal at concentrations between 200 and 5300 ppmv (H₂S loading rates of 7-190 g m^-3 h^-1) present in fouled air. The Fe-EDTA chelate as a single treatment was able to remove nearly 99.99% of the H₂S at inlet concentrations ≤ 2400 ppmv (107 g m^-3 h^-1), while the hybrid system archived undetectable outlet H₂S concentrations (<1 ppmv) at inlet levels of 4000 and 5300 ppmv. At 5300 ppmv, the Fe-EDTA chelate process H₂S removal efficiency decreased to 99.20% due to the limitation of oxygen mass transfer in the Fe(III) regeneration reaction. Under the previous conditions, the pH was required to be controlled by the addition of NaOH, due to the likely occurrence of undesirable parallel reactions. The elemental sulfur yield attained in the physicochemical module was 75-93% with around 80% recovered efficiently as a solid.

Behavior of activated carbons by compound modification in high gravity for toluene adsorption

The rotating packed bed is a chemical apparatus that strengthens mass transfer between phases to enhance their reactivity. It can be used to modify adsorbent materials, greatly improving their chemical properties. This article studies the effect of compound modification of activated carbons in a high-gravity environment on their toluene adsorption. The compound modification includes physical (N2) and chemical modification (HNO3), and the effect of modification is compared between traditional fixed-bed and rotating packed bed modification. The physical characteristics of the activated carbons, including pore size, specific surface area, and morphology are tested by Brunauer–Emmett–Teller and scanning electron microscopy, and the surface functional groups of the activated carbons are determined by Fourier transform infrared spectroscopy and Boehm titration. The results indicate that the activated carbons modified by rotating packed bed have a larger specific surface area (871.5 m2/g) and smaller pore size (0.524 nm), and the content of acidic oxygen-containing groups is 1.5 times that of unmodified activated carbons. The adsorption capacity of the activated carbons compound-modified by rotating packed bed increases by 69% compared with the unmodified activated carbons. The adsorption by the rotating packed bed-compound-modified activated carbons obeys the Freundlich model. The modification of activated carbons by rotating packed bed greatly enhances their specific surface area, pore size, and surface content of oxygen-containing functional groups, markedly improving the adsorption performance and increasing the utilization rate.