Researchers have recently paid a lot of attention to semiconductor photocatalysts, especially ZnO-based heterostructures. Due to its availability, robustness, and biocompatibility, ZnO is a widely researched material in the fields of photocatalysis and energy storage. It is also environmentally beneficial. However, the wide bandgap energy and quick recombination of the photoinduced electron–hole pairs of ZnO limit its practical utility. To address these issues, many techniques have been used, such as the doping of metal ions and the creation of binary or ternary composites. Recent studies showed that ZnO/CdS heterostructures outperformed bare ZnO and CdS nanostructures in terms of photocatalytic performance when exposed to visible light. This review largely concentrated on the ZnO/CdS heterostructure production process and its possible applications including the degradation of organic pollutants and hydrogen evaluation. The importance of synthesis techniques such as bandgap engineering and controlled morphology was highlighted. In addition, the prospective uses of ZnO/CdS heterostructures in the realm of photocatalysis and the conceivable photodegradation mechanism were examined. Lastly, ZnO/CdS heterostructures’ challenges and prospects for the future have been discussed.

In this work, pure ZnO, SnO₂, and ZnO‐SnO₂ nanostructured composites (Z‐S heterostructure) are fabricated by a facile and environmental savvy hydrothermal method at 230°C for 12 hours and followed by high‐temperature annealing. The synthesized samples were examined to analyse the structural and optical characteristics using XRD, TEM, XPS, and UV‐DRS techniques. Investigate the photocatalytic activity (PCA) of pure ZnO, SnO₂, and Z‐S heterostructure for the decolorization of methylene blue (MB) model pollutant in wastewater using visible light irradiation. XRD analysis reveals that ZnO and SnO₂ exhibit hexagonal wurtzite structure and tetragonal rutile structure. TEM micrographs infer the nanorod‐like structure of ZnO, nanoflake‐like structure of SnO₂, and a thin nanosheet‐like structure of Z‐S. XPS analysis evidence for the presence of constitutes elements and Zn⁺², Sn⁺², O⁻² valance states along with environmental peaks in Z‐S heterostructure. The optical band gaps of ZnO (3.37 eV), SnO₂ (3.6 eV), and Z‐S heterostructure (2.84 eV) are inferred by UV‐DRS analysis, together with evidence for the red shift. Under two hours of visible light illumination, the photocatalytic degradation efficiency of MB dye in pure ZnO, SnO₂, and Z‐S heterostructure is 38.55, 32.68, and 82.45%. The formation of a unique Z‐S heterostructure and the maximum departure of charge carriers are the reasons for obtaining robust degradation activity than pristine ZnO and SnO₂. MB dye degradation process in the presence of Z‐S heterostructure photocatalyst, the reusability test findings, and the suggested charge separation technique for customizing Z‐S heterostructure photocatalyst under visible light irradiation is presented.

Clean, safe and acceptable fresh water is fundamental to the existence of life. There is still a serious problem with adequate availability of fresh and quality of water for human consumption. This study, therefore, assesses the relevance of groundwater in the selected sites of villages of Palakonda mandal in the Srikakulam district of Andhra Pradesh, India, for consumption, based on different indices of water quality. Groundwater is the principal source for domestic and irrigation purposes in this region. In order to assess the quality of groundwater, 39 groundwater samples were collected during pre- and post-monsoon season from 2013 to 2016. The concentrations of physicochemical parameters such as pH, electrical conductivity, total dissolved solids, total hardness (TH), Ca(II), Mg(II), fluoride (F⁻), chloride (Cl⁻), dissolved oxygen, total alkalinity and nitrite (NO₂⁻) were analyzed to compute Water Quality Index (WQI). The results of the concentrations were interpreted and compared with WHO (2012) and BIS (2012) standards. Correlation between various parameters was also computed, and the results were presented. The results of WQI computation infer that the groundwater of the selected sites in Palakonda mandal is rated as ‘good’ for human consumption.