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The pillared clays are getting wide attention due to the easiness in tailoring their surface for customized applications. In our laboratory, we have adopted a novel synthetic route to pillar zirconium species within intercalation spaces of bentonite clay through stirring-ageing technique and prepared the zirconium-pillared bentonite clay (ZPBC). A series of experiments conducted to optimize the stirring-ageing time span revealed that 2–4 h span is sufficient for getting a good yield of ZPBC. The synthesized ZPBC was characterized using certain well-developed sophisticated techniques to obtain their physical, structural and morphological properties. The high surface area 109 m2 g−1 noticed for ZPBC is suitable in retaining the chemical moieties of special interest during pollutant removal processes. X-ray fluorescence studies revealed that there is an increase in wt% of Zr (4.76%) in pillared clay compared to Na-bentonite which indicates that Zr has been successfully loaded on the surface of parent clay during pillarization. The mineralogical composition and the gradual changes in the interlayer spacing of parent and pillared clay are well established using X-ray diffraction technique. The Raman spectrum identifies changes in the lattice vibration modes of ZPBC as pillaring takes place. The surface topographical changes that occurred in clay after modification were revealed from the scanning electron microscopy images. The prepared ZPBC were tested successfully for the removal of phosphate from aqueous solution and obtained a maximum adsorption capacity 58.83 mg g−1 at 30 °C.

In our laboratory, we synthesized a novel surface tailored activated charcoal in removing nitrite species from fertilizer industrial effluents. A customized high temperature carbonate-steam activation technique was adopted to develop the sodium carbonate impregnated activated charcoal (SCIAC). The surface properties of the material were determined using SEM, TG and X-RD techniques. Batch adsorption experiments were performed for optimizing various conditions such as solution pH, contact time, temperature and adsorbent dose for maximizing the nitrite adsorption onto SCIAC. Considerably, a very high nitrite adsorption percentage of 83.8 was obtained for an initial nitrite concentration of 5.0 mg/L at pH 3.0. Among the various equilibrium and kinetic models, Freundlich and pseudo-second-order expressions, respectively, were well enough to explain the adsorption processes. In general, it may conclude that the change in surface characteristics of the adsorbent material after the pyrolysis process is highly favorable for effective removal of nitrite ions from aqueous systems. Adsorption capacity of SCIAC was 27.03 mg/g and studies revealed that the material was feasible in removing nitrite from industrial effluents.

In this work, the water quality status of the surface water that lies around the Karamana River basin, Trivandrum urban area, was studied on the basis of the water quality index (WQI) method. The eutrophic condition of the basin is revealed, and proper mitigation strategy was adopted for the removal of phosphate species using pillared clay materials. Proper sampling was carried out in the urban rivers, and various physico-chemical parameters for evaluating the quality of water were analysed. WQI values obtained for these riverine systems are in the range 317.7–3005.1, indicating that the water is not suitable without treatment for any domestic activities. Also, phosphate ions in the range 1.98–20.52 mg/L reflect the dominance of phosphate species in surface water. A proper mitigation strategy was adopted for the selective removal of phosphate ions using adsorption technique by using zirconium-pillared bentonite clay (ZPBC) prepared by the stirring–ageing technique. The batch adsorption experiment performed on simulated phosphate solution shows that for 2.0 g/L of ZPBC a maximum phosphate adsorption capacity of 35.71 mg/g was achieved in 30 min at pH 3.0. The data obtained were used to study models in kinetics and isotherm. The reusability of spent ZPBC for five continuous cycles without major loss in adsorption capacity using 0.025 M Na2CO3 extractant was proved from the desorption study. A single-stage reactor was also designed from the isotherm data and proved to be effective. The applicability of the adsorbent towards phosphate anions was successfully checked in the laboratory using surface water collected and found that the complete removal of phosphate was achieved using 6.0, 8.0 and 10.0 g/L of ZPBC.

The study emphases on the optimization experiments in removing phosphate species from liquid phase using a bentonite–alum system. The bentonite–alum system was prepared with a suitable bentonite–alum ratio after conducting several experiments. The materials were systematically characterized by X-RD, SEM–EDS and FT-IR analytical techniques. Batch-wise adsorption tests were executed to appraise the optimum feasible conditions like pH of the solution, time of contact, initial amount of phosphate species as well as temperature to effect the maximum removal of phosphate species by adsorption process from water and wastewaters. Outer-sphere complexation mechanism may be the main driving force behind the adsorption of phosphate species on to solid phase. The experimental results revealed that for an initial amount of 25 mg L−1 of phosphate at pH 4.0, a maximum amount of 11.52 mg g − 1 (92.2 %) of phosphate species was adsorbed on to bentonite–alum system. The adsorption-kinetics was modelled using pseudo-first-order, pseudo-second-order, Elovich and Weber–Morris intraparticle diffusion models. Langmuir isotherm was the best-fit model to appraise the equilibrium data. A maximum of 58.82 mg g−1 of adsorption capacity was obtained with respect to the adsorption of phosphate species onto bentonite–alum system. The studies also confirmed the viability of the bentonite–alum system in scavenging phosphate from urban river water streams.

This research incorporates iron-loaded crosslinked chitosan (CS) polymeric structure into the interlayer lattice space of Montmorillonite clay (MT) to enhance the phosphate adsorption capacity of MT. The synthesized Fe-loaded crosslinked chitosan montmorillonite composite (Fe-CS-MT) is evaluated effectively for phosphate removal from aqueous media. Batch adsorption experiments optimized the influence of adsorption parameters, i.e., contact time (50 min), solution pH (3), and adsorbent dosage (2 g L−1) for phosphate removal. The experimental results of equilibrium and kinetic studies indicated that phosphate adsorption on Fe-CS-MT follows Pseudo-second-order kinetic and Freundlich isotherm models with a high degree of accuracy. A series of analytical tools used to profile the investigated material's surface features involves CHNS Analyser, SEM-EDX, FTIR, XRD, XRF, UV-Visible Spectrophotometer, TGA, DSC, and surface analysis. The calculations of the thermodynamic study confirmed the endothermic and spontaneous nature of the phosphate adsorption process. This study presents an eco-friendly adsorbent tested in natural conditions to assess the feasibility of removing phosphate from an aqueous phase.

The current river basin monitoring study investigates the standards of the quality of the river and well water in a biodiversity-rich Netravati River basin in Karnataka state, India. Water samples were collected from 16 major sampling sites during pre-monsoon (April), monsoon (August) and post-monsoon (October) seasons in 2017 to ascertain its physico-chemical parameters. The results of the tests were compared with maximum permissible limits proposed by the World Health Organisation drinking water guidelines. The Water Quality Index (WQI) and the Irrigation Water Quality Index (IWQI) using parameters such as Sodium Percentage (Na %), Magnesium Hazard (MH), Permeability Index (PI), Sodium Absorption Ratio (SAR) and Residual Sodium Carbonate (RSC) have been determined to provide a better understanding of its drinking and irrigation water quality. The interpreted WQI values of the water in Netravati River vary from 33.21 to 298.66, which fall in the range of excellent to very poor drinking water quality. In the case of well water, 100% falls under the excellent category. Multiple statistical methods like Principal Component Analysis (PCA) and Pearson correlation analysis were used, and the results of PCA were found to be in a correlation with the results of the Pearson correlation analysis method. The study, as a whole, highlights the importance of the application of PCA, WQI and IWQI as standard methods to evaluate the quality of water. The results of the present study could be used to contemplate regulations to improve the water quality standard and help people living in and around the river basin to understand the current status of the water quality they use for various purposes.

The present study aimed to analyse the influence of physico-chemical properties on zooplankton assemblages and species diversity in a lagoon system. The study was carried out in coral reef lagoon of Kavaratti Island, Lakshadweep Archipelago, India during the monsoon of the year 2017. Zooplankton assemblages, distributed among 56 taxonomic units, were found to be dominated by copepods (63.27%, 34 taxa) followed by cladocerans (11.14%, 7 taxa), ostracods (9.87%, 2 taxa), ciliates (6.23%, 6 taxa), chaetognaths (4.32%, 3 taxa), leptomedusae, (1.25%, 1 taxa), and appendicularians (3.92%, 3 taxa). Copepods assemblages showed maximum density of 14326 ind m−3 from S1, in which leptomedusea was the lowest abundant taxa (284 ind m−3). Shannon–Wiener-index between 3.725–3.860 attested to the fact that the species diversity and richness predominated in lagoon than that in offshore. Canonical Correspondence Analysis revealed the environmental parameters influencing the abundance and occurrence zooplankton community in the study area.

The present work focuses on the quality aspects of riverinesystems in Trivandrum urban area during premonsoon season of 2017along with phosphate removal studies. Altogether, 11 water samples collected from Karamanariver, Killiyar and Parvathy Puthanar canal, andsubsequently analysed for various physic-chemical parameters. In situ measurements made for finding out the parameters such as pH, electrical conductivity, total dissolved solids and dissolved oxygen, which was in the range of 6.6–6.9, 265.6–6317.0 μS/cm, 4.7–65.5 mg/L and BDL-4.9 mg/L, respectively. The biochemical oxygen demand and alkalinity were found to be in the range of BDL-3.8 mg/L and 19.5–53.7 mg/L, respectively. Other parameters such as chloride (1.4–28.1 mg/L), sulphate (177.6–585.0 mg/L), nitrite (BDL-1.95 mg/L), silicate (7.1–27.3 mg/L) and phosphate (BDL-5.5 mg/L) were also determined. The results showed that most of the hydrochemical parameters were found to be within the standard limit prescribed by BIS(2012) except hardness, conductivity, TDS and Phosphate. In general, the study was helpful in evaluating the level of pollution in Trivandrum urban area during pre monsoon season. In the application side, the phosphate removal studies from Parvathy Puthanar were carried out using a novel zirconium impregnated bentonite clay.