Extraction of dye from dry fruit of Rothmannia whitfieldii was carried out using four different extraction methods. Solvent and acid extraction methods gave a colourless supernatant solution after extraction time of 45 minutes at 60˚C. The alkali method gave a deep brown coloured supernatant solution while the aqueous method gave a dark coloured supernatant solution after extraction under the same conditions. From the result of the FTIR spectroscopy characterization of the coloured solutions and the dry powder of Rothmannia whitfieldii fruit, it was observed that only the alkali method extracted what can be called a dye with likely presence of tannins. The result also showed that the possible functional groups present in the supernatant solution after aqueous extraction are same with the functional groups present in the dry pulverized Rothmannia whitfieldii fruit. Hence, aqueous method did not extract any dye. Similarly, a mixture of the solution after aqueous extraction with drops of alkali solution produced a deep brown coloured solution indicating solubility of the dye component in alkali media.

Nylon 6 fabric was dyed with C.I. Acid Yellow 23 at a temperature 50˚C using sodium chloride (NaCl) and citric acid as auxiliaries. The adsorption kinetic mechanism was studied using two models. Results of the UV-Vis spectroscopy indicated that colour yield of C.I. Acid Yellow 23 reduced when more than 1% (acid) and 5% (salt) concentration were used respectively for dyeing. NaCl however had the most inhibitive effect on the dye colour yield. The adsorption kinetics mechanism result fitted the pseudo-second-order-kinetic model with R 2 of 0.993.

Acid-Base Indicator, Turmeric Rhizome (Curcuma longa) was extracted from the root of a turmeric plant. The turmeric was peeled, washed and dried in an oven at 60˚C. It was ground into powder and soaked in hot and cold ethanol for the extraction. The extract was filtered and part of it was concentrated to yield a reasonable quantity of turmeric indicator. On standardization of acid with a base, 0.05 M base respectively of Sodium hydroxide (NaOH), sodium carbonate (Na 2 CO 3 ) and Disodium borate (B 4 Na 2 O 7 ) were used. Hot and cold extracts of turmeric were used as indicators and were compared with methyl orange and phenolphthalein. On the preliminary test carried out, hot and cold turmeric indicator showed yellow colour in acid medium and orange colour in the base. Methyl orange showed red colour in acid but yellow in the base, phenolphthalein was colourless in acid but pink in the base. During titration there were colour changes at the end points in the entire test carried out. The average volumes at ends points were calculated, the molar concentrations and mass concentrations of the acids used were also determined. The results showed that there was no difference between the natural indicators used and the existing synthetic indicators which are toxic to our environment.

Interlocking paving bricks were produced with plastic wastes and sand using heating technique without other cementing or binding agent and water. Waste single-use plastics - polyethylene terephthalate (PET) bottles and low density polyethylene (LDPE) sachet water films used respectively were sourced from dump site, washed, air dried, melted and mixed with sand of not more than 2 mm particle size to produce interlocking paving brick (IPB). Sand-plastic mix ratios of 1:1, 1:3 and 3:1 and metal mould of 190 × 90 × 90 mm dimension were used. The compressive strength, flexural tensile strength, abrasion and water-absorption test results showed that IPB from LDPE-sand composite has better mechanical performance than IPB from PET-sand composite for all the mix ratios. The IPB from LDPE-sand composite of 3:1 mix ratio had a compressive strength of 31.11 N/mm2 and water absorption of 0.33% of its dry weight whereas its PET counterpart had compressive strength of 13.1 N/mm2 and water absorption of 0.5%. Scanning electron microscope (SEM) and abrasion results also showed that LDPE had better compatibility with sand particles. Waste single-use plastics can be used to produce high quality interlocking paving brick without cement and water and as well reduce the menace of waste PET bottles and LDPE films in our environment.

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