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• The 3D structure carbon aerogel with highly dispersed SnO 2 nanoparticles was synthesized. • The sorbent exhibited high Hg0 and H 2 S capture capacities and excellent regeneration performance. • The core-shell structure is beneficial for the resistance to H 2 O. • E-R adsorption mechanism of H 2 S and Hg0 was conformed. A seaweed-templated pathway was developed for the controllable synthesis of SnO 2 /carbon aerogel for the simultaneous removal of Hg0 and H 2 S in natural gases, where the SnO 2 nanoparticles with an outer diameter of 4–20 nm were highly dispersed and conjoined by graphitic carbon, forming a 3D core-shell structure with a developed pore network. The synthesized sorbent performed a complete removal of Hg0 and H 2 S at a high space velocity of 70,000 h−1 and showed resistance to water. At 5% breakthrough, the Hg0 and H 2 S capture capacities reached as high as 10.37 mg g−1 and 392.23 mg g−1, respectively, which are much higher than those of the existing commercial sorbents. More importantly, the spent sorbent could be easily regenerated without significant performance degradation over five cycles. The 3D interconnected macro- and mesopores are beneficial for the Hg0 and H 2 S removal at a high space velocity, and the core-shell structure is conducive to prevent poisoning from water. The Hg0 and H 2 S removal over the SnO 2 /aerogel conforms to the E-R mechanism, where H 2 S is first adsorbed and dissociated on the SnO 2 surface to produce active sulfur species, and the adsorbed sulfur then reacts with gaseous Hg0 to form HgS. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A facile method was developed to synthesize regenerable and H 2 O resistance sorbent for Hg0 removal. • The Ag nanoparticles were successively confined inside the mesoporous channels of MCM-41 molecule sieve. • The nanoconfinement effect is conducive to excellent Hg0 removal performance and regeneration ability. • The high hydrophobicity of Ag/MCM-41 is beneficial for the resistance to H 2 O. Abstract A facile passivation treatment and amino functionalized method was developed for controllable synthesis of effective and water-resistant Ag/MCM-41 composite sorbent for Hg0 removal in natural gas. The Ag nanoparticles were successively confined inside the mesoporous channels of MCM-41 molecule sieve with an average diameter of 3 nm. The synthesized sorbent was found to achieve a complete removal of Hg0 at high space velocity of 50,000 h−1 in ambient temperature. At 5% breakthrough, the Hg0 capture capacity of 1% (wt%) silver loaded Ag/MCM-41 was as high as 6.64 mg·g−1, which is much higher than the sample of Ag loaded outside of the pore channels (S-Ag/MCM-41) and other existing commercial sorbents. The H 2 O has negligible inhibitory effect on Hg0 removal performance of Ag/MCM-41. In addition, the spent Ag/MCM-41 could be easily regenerated without significant performance degradation over five cycles. We considered the high Hg0 capture efficiency, large adsorption capacity and excellent regeneration performance of Ag/MCM-41 are contributed to the nanoconfinement effect of mesoporous channels of MCM-41 molecule sieve which effectively prevented the growth and agglomeration of Ag nanoparticles. The good hydrophobicity of Ag/MCM-41 is beneficial for the high resistance to H 2 O. This work represents a giant step toward the preparation of effective sorbent for practical applications of Hg0 removal in natural gas. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel sorbent was prepared for simultaneous removal of H 2 S and Hg0 in natural gas. • H 2 S and Hg0 capacities of 1Cu1Zn/SBA-15 were 296.78 mg·g−1 and 12.75 mg·g−1 at 10% breakthrough. • The 1Cu1Zn/SBA-15 sorbent exhibited excellent the regeneration performance over 5 cycles. • the S n 2− formed by chemisorption of H 2 S are the active sites for Hg0 capture. Inspired by the fact that H 2 S can easily decompose on some metal oxides to form sulfur species and the resulting products are usually used as Hg0 removal active sites, a novel Cu-Zn mixed oxide supported SBA-15 zeolite was controllably synthesized for simultaneous removal of Hg0 and H 2 S. The Cu-Zn nanoparticles with a particle size range of 4.4–5.0 nm were successfully confined and uniformly dispersed in the two-dimensional mesopores of SBA-15. The obtained 1Cu1Zn/SBA-15 adsorbent presented an outstanding H 2 S and Hg0 removal efficiencies at 30 °C and 30,000 h−1, and the H 2 S and Hg0 capture capacities reached to 296.78 mg·g−1 and 12.75 mg·g−1 at a 10% breakthrough. In addition, the spent adsorbent could be regenerated in a 5% O 2 and 95% N 2 atmosphere at 600 °C without obvious degradation of adsorption capacities over five cycles. We considered that the doping effects of Cu-Zn oxides were beneficial for its excellent H 2 S and Hg0 removal performance at low temperatures, and the nano-confinement effect of SBA-15 was conducive to prevent the oxides nanoparticles from agglomeration in the regeneration process, thus achieving the outstanding regeneration performance. Furthermore, the polysulfide polymer formed by chemisorption of H 2 S on the Cu-Zn oxides surface was confirmed to be the Hg0 active sites, which could react with gaseous mercury to form HgS. This work provided an effective way for simultaneous removal of H 2 S and Hg0 in natural gas by confining nano-sized active metal oxides into the mesopores of zeolites. [ABSTRACT FROM AUTHOR]

[Display omitted] • A 3D network structure carbon aerogel of PPD-Cu/CA for deep removal of COS from natural gas. • Para-phenylenediamine doping improves the pore structure of the adsorbent and introduces basic pyridine nitrogen. • The introduction of p-phenylenediamine increases the number of moderate basic sites on the adsorbent. • The adsorbent exhibits excellent high space velocity resistance and water resistance. • The COS adsorption capacity of the optimized PPD-Cu/CA adsorbent can reach 18.6 mg/g at 40 °C. For the purpose of overcoming the difficulty of low removal rate of COS at low temperatures, N-doped copper oxide-supported carbon aerogels were prepared with sodium alginate as a carbon source for deep removal of COS (about 20 ppm) from natural gas. By exploring the effects of different nitrogen sources (urea, melamine and p-phenylenediamine), carbon–nitrogen ratio and carbonization temperature, p-phenylenediamine-doped copper oxide-loaded carbon aerogels (PPD-Cu/CA) with both excellent catalytic hydrolysis of COS and adsorption were prepared. The COS adsorption capacity of optimized PPD-Cu/CA was 18.6 mg·g−1 with 0.94 %Vol of water content at 40 °C, meanwhile, the COS removal efficiency at 40,000 and 70,000 mL·g−1·h−1 could reach 100 % and 94.6 %, respectively, showing excellent high space velocity resistance. Combined with characterization and experimental results, the introduction of p-phenylenediamine enriched the pore structure of the carbon carrier, increased the neutral base site, and played a positive role in the adsorption and hydrolysis of COS. This study provides a new insight into the removal of carbonyl sulfur from natural gas. [ABSTRACT FROM AUTHOR]

• At low temperature the 5%K 2 O-Cu/CA achieved good COS conversion performance. • The surface hydroxyl group is enriched by K loading. • The escaped H 2 S could be adsorbed to be S2- and SO 4 2- on 5 %K 2 O-Cu/CA. • The adsorbent could be regenerated by N 2 regeneration process. COS in natural gas is difficult to be effectively removed at room temperature. Catalytic hydrolysis is a promising method, however, the discrepancy of catalytic active site as well as deactivation factors are the restricting factors. In this paper, the CuO load and alkali metal modification was successfully prepared on carbon aerogel with more mesoporous structure(5 %K 2 O-Cu/CA). The doping of K could improve the pore structure of the sample and is more conducive to the storage of sulfate, obtaining good anti-poisoning properties. Meanwhile, the K load achieved enriched surface hydroxyl groups, which played an important role in COS conversion, and provided enough electronic electron transfers to accelerate the H 2 O dissociation, producing more hydroxyl groups. Then the adsorbed COS could be efficiently captured by the increasing number of weak basic sites at low temperature. Furthermore, after COS transformation the escaped H 2 S could be subsequently adsorbed on 5 %K 2 O-Cu/CA surface and converted to be S2- and SO 4 2- on CuO surface. Finally, the adsorbent capacity and deactivation were studied, and the N 2 regeneration method owns the higher sulfur capacity of 6.01 mg/g with a COS removal efficiency of 100 % for the first time. [ABSTRACT FROM AUTHOR]

The silver loaded adsorbents has been demonstrated to be an exciting approach towards Hg 0 removal from natural gas streams, its Hg 0 removal efficiency and capacity is closely related to the valence state, particle size and dispersity of silver particles. This study focused on chemical reduction methods in aqueous solutions to synthesize Ag/4A zeolite, and the influences of ultrasonic and protective additives were investigated to reduce the size of silver particles. The characterization results showed that silver particles are loaded on the surface of 4A zeolite with highly dispersed elemental form, ultrasonic and addition of stearic acid as protective additives are the effective ways to produce small nano-scale silver particles close to 15 nm. Meanwhile, the silver particles on the surface of Ag/4A zeolite are the active sites for Hg 0 adsorption which can react with Hg 0 to form Ag-Hg amalgam alloy. The silver lattices disappeared from the outer boundary to the interior of the particles after Hg 0 adsorption, which indicated that the Hg 0 firstly reacts with the nano-scale silver on the surfaces and then gradually penetrates into the interior of silver particles. The Hg 0 removal efficiency of prepared Ag/4A zeolite adsorbents was higher than 96% after 200 min adsorption at 30 °C, and adsorption capacity reached to 5.985 mg/g. Furthermore, the regeneration and reutilization results indicated that the Hg 0 adsorption performance remained stable after 5 reuse cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • The discrepancy of the application environment demands different characteristics of adsorbents. • The demercuration barriers, stabilization of mercury-containing compounds and regeneration are summarized. • Structure, hydrophobic groups and modification could purposefully overcome the bottleneck of H 2 O and SO 2. • The thermal treatment accompanied by different components has been widely adopted as an efficient approach for regeneration. Gaseous elemental mercury (Hg0) is a hazardous global pollutant and difficult to curb. Adsorbent is now attracting great attention in capturing Hg0 because of its recovery and system flexibility. However, the discrepancy of the application environment and competitive gas demand differential treatments on the adsorbents. In this review the current situation of Hg0 removal on different kinds of adsorbents in coal combustion flue gas, smelting flue gas and natural gas are focused. Hydrophobic groups, hydrophobic materials and modification of sulfur/selenium pretreatment and metals loading could purposefully and effectively overcome the problem of H 2 O and SO 2. Stabilization of the mercury-laden compounds, toxicity tests of mercury-containing compounds and leaching characteristics could provide a practical perspective to the safe disposal of mercury-containing waste, reducing the risk of mercury contamination. Additionally, separation, regeneration, and recovery, are explored and summarized, in which the thermal treatment accompanied by different components has been widely adopted as an efficient approach to recover the adsorption ability. Finally, a basic understanding and outlook on demercuration is put forward. [ABSTRACT FROM AUTHOR]

• The Au/MCM-48 absorbent was controllable synthesized for Hg0 removal in natural gas. • Ultrafine Au nanoparticles were embedded in the three-dimensional channels of MCM-48. • The Au/MCM-48 absorbent exhibited excellent tolerance for H 2 O and H 2 S. • The Hg0 adsorption capacity of Au/MCM-48 is up to 7.23 mg∙g−1 at 5% breakthough. • The spent absorbent could be regenerated without distinct degradation over 5 cycles. The H 2 O and H 2 S in natural gas are frequently deemed to have inhibitory influences on Hg0 removal performance of most noble metal based Hg0 absorbents, it is extremely significant to develop an efficient and regenerable Hg0 removal absorbent with excellent H 2 S and H 2 O tolerance. In the work, the Au/MCM-48 absorbent was controllable synthesized using a facile yet robust method for Hg0 removal in H 2 S and H 2 O containing natural gas. The ultrafine Au nanoparticles with a diameter of 1.4 nm were embedded and uniformly dispersed in the three-dimensional channels of MCM-48. The absorbent of 1 wt% Au achieved a complete Hg0 capture performance at 60,000 h−1 and 30 °C by forming Au-Hg amalgam, and its Hg0 adsorption capacity achieved to 7.23 mg∙g−1 at 5% breakthrough. The spent sample could be easily regenerated by thermal treatment without distinct degradation over 5 cycles. The introduction of H 2 S and H 2 O in gas flow had an inappreciable impact on Hg0 removal performance over the Au/MCM-48 absorbent. The excellent Hg0 adsorption efficiency, outstanding capture capacity and good regeneration performance of the absorbent due to the nano-confinement of MCM-48 channels, which prevents Au nanoparticles from growing and agglomerating. Excellent H 2 O tolerance is attributed to the good hydrophobicity of MCM-48 modified by trimethylchlorosilane, and the high H 2 S tolerance is due to the fact that the Au nanoparticles lack reactivity toward H 2 S. This work provides a promising method for the preparation of effective and regenerable absorbents for demercuration in H 2 S and H 2 O containing natural gas. [ABSTRACT FROM AUTHOR]

• A regenerable and H 2 S resistance Hg0 removal sorbent was synthesized using fulvic acid. • The Ag nanoparticles were confined and embedded in the carbon nanosheets. • The special core-shell structure of Ag/Fvs is beneficial for the tolerance to H 2 S. • The nanoconfinement of carbon layer is conducive to regeneration performance. The migration and agglomeration of Ag nanoparticles during high temperature regeneration processes were generally considered the key contributor for the decreasing of Hg0 removal performance over Ag-based sorbents. In this work, a complexation pathway was developed for controllable synthesis of Ag loaded carbon nanosheet (Ag/Fvs) using fulvic acid as template and carbon source. The elemental Ag nanoparticles were highly dispersed and embedded in the carbon nanosheet with an average diameter of 7.12 nm and formed a special core-shell structure. The synthesized sorbent achieved a complete Hg0 removal in H 2 S containing natural gas at ambient temperature. At 1% breakthrough, the Hg0 capture capacity of Ag/Fvs was as high as 1.36 mg·g−1, which is much higher than the sample prepared by traditional impregnation method (I-Ag/Fvs, 0.98 mg·g−1) and other existing commercial sorbents. More importantly, the spent Ag/Fvs could be easily regenerated by thermal treating process, its Hg0 capture capacity only slightly decreased by 5.8% after 4 cycles. We considered the carbon layer prevented Ag nanoparticles from poisoning by H 2 S, and more active sulfur sites for Hg0 capture could be formed on porous carbon nanosheets by chemical adsorption of H 2 S, which is beneficial for the strong tolerance to H 2 S. The excellent regeneration performance of Ag/Fvs mainly attributed to the nanoconfinement of carbon layer, which is conducive to prevent the agglomeration of Ag nanoparticles during high temperature regeneration processes. This work represented a practical and efficient pathway to utilize the cheap fulvic acid for applications of Hg0 removal in H 2 S containing natural gas. [ABSTRACT FROM AUTHOR]