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Geosynthetic clay liners (GCLs) are mostly used as flow barriers in landfills and waste containments due to their low hydraulic conductivity to prevent the leachate from reaching the environment. The self-healing and swell-shrink properties of soft clays (expansive soils) such as bentonite enable them as promising materials for the GCL core layers. However, it is important to modify their physico-chemical properties in order to overcome the functional limitations of GCL under different hydraulic conditions. In the present study, locally available black cotton soil (BCS) is introduced in the presence of an anionic polymer named carboxymethyl cellulose (CMC) as an alternative to bentonite to enhance the hydraulic properties of GCL under different compositions. The modified GCL is prepared by stitching the liner with an optimum percentage of CMC along with various percentages of BCS mixed with bentonite. Hydraulic conductivity tests were performed on the modified GCL using the flexi-wall permeameter. The results suggest that the lowest hydraulic conductivity of 4.58 × 10−10 m/s is obtained when 25% of BCS is blended with bentonite and an optimum 8% CMC and further addition of BCS results in the reduction of the hydraulic conductivity. HIGHLIGHTS Modification of bentonite with locally available black cotton soil and caboxymethyl cellulose polymer.; Enhancement of hydraulic performance of modified geosynthetic clay liner.; Sodium content is low in the modified bentonite beyond the optimum percentage of black cotton soil blended with carboxymethyl cellulose polymer.;

As the short- and long-term impacts of climate change are becoming more visible at smaller regional scales, frequent occurrence (absence) of erratic precipitation as well as water scarcity issues can be identified as reliable indicators for predicting meteorological droughts. A supervised declaration of meteorological drought based on available precipitation data requires an understanding of reliability and consistency of drought indices for appropriate severity classification. An attempt has been made in this study to critically evaluate the performance of six popular drought indices namely, Standardized Precipitation Index (SPI), China Z Index (CZI), Modified China Z Index (MCZI), Deciles Index (DI), Rainfall Anomaly Index (RAI), and Z-Score Index (ZSI) for four districts in Tamil Nadu falling under arid (Karur), semi-arid (Cuddalore), dry sub-humid (Kanyakumari) and moist sub-humid (Coimbatore) conditions based on 120 years of precipitation records. Results showed that the SPI and CZI provided similar quantification of drought events (about 18% of the total months) irrespective of their climatic considerations while ZSI and RAI resulted in overestimation of drought severity (about 30–47%). Based on the classification strategy adopted for the selected indices, a framework for drought vulnerability assessment is proposed in conjunction with the estimated drought severity classifications. HIGHLIGHTS An attempt is made in this study to critically evaluate the performance of six different drought indices.; SPI, CZI, MCZI, DI, RAI and ZSI are calculated for four districts in Tamil Nadu.; SPI and CZI provided similar quantification of drought events irrespective of the regional scale climatic considerations.; ZSI and RAI resulted in overestimation of drought severity.; A framework for the drought vulnerability assessment is provided.;

Performance of green treatment systems such as adsorption to treat textile effluents often suffers lack of longevity and efficiency due to the presence of complex compounds of varying reactivity. There is scope for improving the operational efficiency of such processes using real-time monitoring systems. The present study aimed to evaluate the performance of an activated biosorbent prepared from the leaves of Acalypha indica for treating textile industry effluent by simulating process control with real-time monitoring. Batch experiments were performed with synthetic and real-time dye effluents to identify the optimum conditions (pH = 3.0, dosage = 1.0 g/L; time = 1 h) for the highest adsorption capacity (6 mg g−1 and 2 mg g−1). The evaluation of physical parameters suggested best fit for Freundlich isotherm model and pseudo-second-order kinetic model. The LabVIEW-based simulation control system enabled close monitoring of pH and temperature during the process. Based on the inputs, an alteration of initial pH has resulted in substantial reduction in chemical oxygen demand (COD) (73.91%), turbidity (52.43%) and total dissolved solids (TDS) (19.43%). The average incremental increase was highest for COD (45.80 ± 0.06%) compared to TDS (10.13 ± 0.06%) and turbidity (−1.74 ± 0.03%) for varying dosage (3 g to 11 g). The proposed framework for incorporating a process-control-based monitoring system can help to achieve better performance. HIGHLIGHTS Activated carbon produced from the leaves of Acalypha indica as a biosorbent.; Adsorption isotherm provides best fit with Freundlich model.; Adsorption kinetics indicate that the textile effluent follows pseudo-second-order kinetics.; LabVIEW has been used for the measurement of pH and temperature of the effluent.; Adjustment of the initial pH led to substantial reduction in the COD, TDS and turbidity.;