Optical chemical sensors have promoted escalating interest in the determination of various pollutants in the environment, which are creating toxicity and may cause serious health problems. This review paper focuses particularly on the recent progress and developments in this field; the working principles and basic classes of optical chemical sensors have been briefly described.
A D-shaped polarization-maintaining fiber (PMF) as fiber optic sensor for the simultaneous monitoring of strain and the surrounding temperature is presented. A mechanical end and edge polishing system with aluminum oxide polishing film is utilized to perform sequential polishing on one side (lengthwise) of the PMF in order to fabricate a D-shaped cross-section. Experimental results show that the proposed sensor has high sensitivity of 46 pm/µε and 130 pm/°C for strain and temperature, respectively, which is significantly higher than other recently reported work (mainly from 2013) related to fiber optic sensors. The easy fabrication method, high sensitivity, and good linearity make this sensing device applicable in various applications such as health monitoring and spatial analysis of engineering structures.
The Hattar industrial estate in the Haripur district, Khyber Pakhtunkhwa (KPK), Pakistan, is investigated for the groundwater potential and aquifer vulnerability using vertical electrical sounding (VES) data, borehole logs, and hydrochemical analysis. A total of eight VES points were acquired in the Haripur region using Schlumberger configuration. The interpreted VES models are further constrained by four borehole logs to delineate comprehensive information of the thin lithological layers, subsurface layers configuration, and spatial extent in the area. A quantitative interpretation based on the VES and the borehole data suggests six main subsurface layers: (i) soil cover, (ii) gravel, (iii) clay, (iv) clay with gravel, (v) silty-clay, and (vi) sand with boulder in the study area. A fence diagram is also generated to provide a detailed paleo-depositional model of the subsurface layers. The interpreted VES data is utilized to compute aquifer thickness, longitudinal conductance, and transverse resistance within the study area. The lateral extent and protective capacity for the aquifer were inferred from these measurements. The aquifer thickness is relatively low in the central and eastern parts ranging from 10 m to 11 m. The longitudinal conductance map shows values greater than 2 mhos from the central region to northern one. This is indicative of moderate to good protective capacity for the aquifer and is less vulnerable to infiltration of Hattar industrial polluted fluid. However, the values less than 0.19 mhos in the southwest and east are indicative of weak protective capacity with risk of contamination. The hydrochemical analysis of the surface and subsurface water is carried out at eleven locations to identify the water quality within the study area. The chemical analysis of the water shows the presence of the high concentration of magnesium, bicarbonate, and chlorine away from the World Health Organization (WHO) standard.
Water scarcity in mass populated areas has become a major global threat to the survival and sustainability of community life on earth, which needs the prompt attention of technological leadership. Solar evaporation has emerged as a renewable energy resource and a novel technique for clean water production and wastewater treatment. Indeed, mounting a scalable solar evaporator including high evaporation efficiency and thermal management remains a significant challenge. Herein, we demonstrate a self-floatable, ecofriendly polypyrrole/wood sponge-based (PPy@WS) steam generator. The low-cost and easy to fabricate evaporator system consists of a single-step in situ polymerization of a 2-D (two-dimensional) hydrophilic wood sponge abundantly available for commercialization. The as-prepared PPy@WS solar evaporator exhibits excellent wettability and is super hydrophilic (contact angle ∼ 0), salt-resistant, and has an excellent light absorption of ∼94% due to omnidirectional diffusion reflection in PPy Nanoparticles (NPs). The capacity of the PPy@WS evaporator to absorb broadband solar radiation and convert it into thermal energy has enabled it to achieve excellent surface temperature (38.6 °C). The accumulated heat can generate vapors at the rate of 1.62 kg·m−2·h−1 along with 93% photothermal conversion efficiency under one sun (1 kW·m−2). Moreover, the presented prototype possesses the capability to be installed directly without the use of any complex protocol to purify seawater or sewage with an efficient rejection ratio of primary metal ions present in seawater (approximately 100%). This simple fabrication process with renewable polymer resources and photothermal materials can serve as a practical model towards high-performance solar evaporation technology for water-stressed communities in remote areas.
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