Advanced oxidation processes (AOPs) based on peroxydisulfate (PDS) or peroxymonosulfate (PMS) activation have attracted much research attention in the last decade for the degradation of recalcitrant organic contaminants. Sulfate (SO₄^•−) and hydroxyl (^•OH) radicals are most frequently generated from catalytic PDS/PMS decomposition by thermal, base, irradiation, transition metals and carbon materials. In addition, increasingly more recent studies have reported the involvement of singlet oxygen (¹O₂) during PDS/PMS-based AOPs. Typically, ¹O₂ can be produced either along with SO₄^•− and ^•OH or discovered as the dominant reactive oxygen species (ROSs) for pollutants degradation. This paper reviews recent advances in ¹O₂ generation during PDS/PMS activation. First, it introduces the basic chemistry of ¹O₂, its oxidation properties and detection methodologies. Furthermore, it elaborates different activation strategies/techniques, including homogeneous and heterogeneous systems, and discusses the possible reaction mechanisms to give an overview of the principle of ¹O₂ production by activating PDS/PMS. Moreover, although ¹O₂ has shown promising features such as high degradation selectivity and anti-interference capability, its production pathways and mechanisms remain controversial in the present literatures. Therefore, this study identifies the research gaps and proposes future perspectives in the aspects of novel catalysts and related mechanisms.

Groundwater is the most important water resource, on which depends human geo-economic development and survival. Recent environmental changes and anthropogenic activities render groundwater severely vulnerable. Groundwater in Central Sindh, Pakistan, is facing a similar situation. Hydrogeochemical characteristics of the groundwater in the said region were investigated by analyzing 59 groundwater samples via agricultural and drinking indices, using various statistical methods and graphical approaches to identify factors affecting groundwater. Major reactions occurring in the groundwater system were quantified by hydrogeochemical modeling. A statistical summary reveals the abundance of cations is Na⁺ > Ca²⁺ > Mg²⁺ > K⁺, while the abundance of anions is HCO₃⁻ > Cl⁻ > SO₄². Groundwater chemistry is mainly of rock dominance. Correlation analysis and graphical relationships between ions reveal that ion exchange and rock weathering such as the dissolution of halite, albite, and dissolution of carbonate minerals are important rock–water interactions, governing the evolution of groundwater chemistry. Hydrochemical facies are predominantly of mixed CaMgCl and Na-Cl type, with few samples of Ca-HCO₃ type, which constitutes fresh recharged water. Based on the Water Quality Index (WQI), 28.82% samples were found to be unsuitable for drinking. A United States Salinity Laboratory (USSL) diagram, Wilcox diagram, and other agricultural indices indicate that majority of the groundwater samples fall within the acceptable range for irrigation purposes.

Mercury (Hg) contamination of wastewater streams as a result of anthropogenic activities is a great threat to living organisms due to its acute toxicity. Therefore, current research is focused on the development of effective remediation technologies to protect human health and the environment. In this study, a novel chemical modification route was applied for the multi-functionalization of biochar in order to make it more efficient and selective for Hg(II) removal from aqueous solution. The amino-grafted modified biochar (AMBC) having multifunctional groups on its surface was successfully synthesized through the activation of excessively available carboxylic groups (–COOH) on pre-oxidized biochar (BC–COOH). The maximum Hg(II) adsorption capacity for the optimized amino-BC2 sample was 14.1 mg g⁻¹, which was almost twice as that for pristine biochar (BC, 7.1 mg g⁻¹). SEM, FTIR, and XPS techniques were applied for the confirmation of chemically grafted amino groups as well as the presence of residual –COOH groups on the biochar surface. Based on the batch adsorption data, adsorption kinetics and isotherms as well as XPS results, it was concluded that the Hg(II) removal mechanism was purely driven by chemisorption such as electrostatic interaction, surface complexation, ion exchange with no precipitation and crystalline material being adsorbed on the adsorbent surface. These research findings not only provide a suitable adsorbent for decontamination of Hg(II) from aqueous solution but also offer a new route for the multi-functionalization of biochar in order to make environment-friendly and inexpensive adsorbents.

Alteration in Land Use/Cover (LULC) considered a major challenge over the recent decades, as it plays an important role in diminishing biodiversity, altering the macro and microclimate. Therefore, the current study was designed to examine the past 30 years (1987–2017) changes in LULC and Land Surface Temperature (LST) and also simulated for next 30 years (2047). The LULC maps were developed based on maximum probability classification while the LST was retrieved from Landsat thermal bands and Radiative Transfer Equation (RTE) method for the respective years. Different approaches were used, such as Weighted Evidence (WE), Cellular Automata (CA) and regression prediction model for the year 2047. Resultantly, the LULC classification showed increasing trend in built-up and bare soil classes (13 km² and 89 km²), and the decreasing trend in vegetation class (−144 km²) in the study area. In the next 30 years, the built-up and bare soil classes would further rise with same speed (25 km² and 36.53 km²), and the vegetation class would further decline (−147 km²) until 2047. Similarly for LST, the temperature range for higher classes (27 -< 30 °C) increased by about 140 km² during 1987–2017, which would further enlarge (409 km²) until 2047. The lower LST range (15 °C to <21 °C) showed a decreasing trend (−54.94 km²) and would further decline to (−20 km²) until 2047 if it remained at the same speed. Prospective findings will be helpful for land use planners, climatologists and other scientists in reducing the increasing LST associated with LULC changes.

Simultaneous activation of H₂O₂ and persulfate by nanoscaled Fe⁰ shows synergistic effect for degradation of p-nitrophenol with generating both hydroxyl and sulfate radicals in a wide initial pH range.