Management of solid wastes is considered as an economic and environmental issue in the building stone industry. The current study uses raw and calcined calcareous sludge, generated in the stone cutting factories, in order to remove sulfur dioxide. Sludge characterization has been performed, using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analyses. The removal experiments of sulfur dioxide have conducted under different humid contents and adsorbent doses. The results showed that the higher the adsorbent dosage and humidity content, the greater the SO2 adsorption.. The calcination process at temperatures of 400, 500, 600, and 700℃ revealed that with rising calcination temperature and humidity content, the adsorbent capability is enhanced considerably. This method could be developed for the management of stone sludge produced from the stone cutting industry through its conversion into an effective and low-cost adsorbent for desulfurization process.

Biochar has been used to remove heavy metals from aqueous solutions. In this study, a sulfurized wood biochar (SWB) by direct impregnation with elemental sulfur was produced and evaluated along with pristine wood biochar (WB) for adsorption characteristics and mechanism of mercury. Mercury adsorption by WB and SWB was well described by Langmuir model and pseudo second order model and the maximum adsorption capacities of WB and SWB were 57.8 and 107.5 mg g⁻¹, respectively. Intraparticle diffusion model showed that mercury adsorption was fast due to boundary layer and slow adsorption due to diffusion into biochar pores. Although, mercury adsorption by both WB and SWB was predominantly influenced by the pH, temperature, salt concentration, and biochar dosage, the SWB showed a relatively stable mercury adsorption compared to WB under different conditions, suggesting the strong affinity of SWB for mercury. The XPS analysis showed different adsorption mechanisms of mercury between WB and SWB. In particular, mercury adsorption in WB was due to Hg-Cπ bond formation and interaction with carboxyl and hydroxyl groups, whereas in SWB it is primarily due to mercury interaction with C-SOₓ-C and thiophenic groups in addition to Hg-Cπ bond formation and interaction with carboxyl groups. The SEM-EDS mapping also demonstrated that mercury in SWB was related to carbon, oxygen and sulfur. Overall, the sulfurized biochar was effective for removing mercury from aqueous solution, and its direct production through pyrolysis with elemental sulfur impregnation of wood chips could make it an economic option as absorbent for treating mercury-rich wastewater.

Dyeing wastewaters are toxic and carcinogenic to both aquatic life and human beings. Adsorption technology, as a facile and effective method, has been extensively used for removing dyes from aqueous solutions for decades. Numerous researchers have attempted to seek or design alternative materials for dye adsorption. However, using various novel adsorbents to remove dyes has not been extensively reviewed before. In this review, the key advancement on the preparation and modification of novel adsorbents and their adsorption capacities for dyes removal under various conditions have been highlighted and discussed. Specific adsorption mechanisms and functionalization methods, particularly for increasing adsorption capacities are discussed for each adsorbent. This review article mainly includes (1) the categorization, side effects and removal technologies of dyes; (2) the characteristics, advantages and limitations of each sort of adsorbents; (3) the functionalization and modification methods and controlling mechanisms; and (4) discussion on the problems and future perspectives about adsorption technology from adsorbents aspects and practical application aspects.

Graphene with atomic layer of sp²-hybridized carbon atoms in a hexagonal structure has attracted multidisciplinary attention since its discovery. Due to the inherent advantages of large specific surface area and abundant functional groups, its derivative graphene oxide (GO) nanomaterials have achieved large-scale development in effective pollution treatment. In the past few years, novel GO-based nanomaterials through coupling with other nanomaterials have been synthesized with significant process and applied for efficient elimination of different kinds of pollutants. This paper aims to summarize recent research results on the excellent removal ability of GO-based nanomaterials for various heavy metal ions in aqueous solutions. The synthesis, adsorption process characteristics and interaction mechanism of the adsorbent are emphasized and discussed. The effects of various environmental conditions are outlined. At last, a brief summary, perspective and outlook are presented. This review is intended to provide some thrilling information for the design and manufacture of GO-based nanomaterials for the elimination of heavy metal ions from wastewater in environmental pollution management.