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Abstract This present study investigates the heat-assisted extraction (HAE) of bioactive antioxidants from Enantia chlorantha stem bark (ECSB). The effects of process parameters of operating temperature (OT: 35–55 °C), extraction time (ET: 100–200 min) and solid: liquid ratio (S/L: 1:20–1:50 g/mL) are determined on the total polyphenol content (TPC), antioxidant activity (AA) and extract yield (EY) using the D-Optimal design. Multi-criteria optimization is also conducted to determine the HAE optimum conditions. The integrated process for E. chlorantha stem bark extracts (ECBEs) production is thereafter designed with the optimum HAE conditions and techno-economically analysed. Three industrial ECBEs production setups (5, 100 and 1000 L extractor capacities) are analysed for probable scale-up and the risk & sensitivity analyses are conducted via Monte Carlo simulation. The HAE parameters affect the extraction process significantly. The OT, ET and S/L that maximize the TPC, AA and EY simultaneously are: OT = 54.10 °C, ET = 120.16 min and S/L = 1:50 g/mL. The 1000 L plant extractor setup is the most economical capacity having the least unit production cost (UPC) of 763.52 US$/kg ECBEs. The certainty of achieving 763.52 US$/kg ECBEs for the 1000 L capacity is 55.43% and the only variable with negative contribution (− 37.9%) on ECBEs UPC is the extract recovery variable.

The wastewater from paint manufacturing industry contains high quantity of pollutants that are generated from washing equipment, as well as chemical additives. Hence, coagulation–flocculation was applied in the present study to evaluate the performance of some natural coagulant derived from Hibiscus esculentus L,(okra) Detarium microcarpum,(sweet dater) Xanthosoma (cocoyam) and Crassostrea Virginica, (oyster shell) in the removal of turbidity from paint wastewater (PW). The coagulants were characterized using Fourier transform infrared spectrometer (FTIR), Scanning electron microscopy (SEM) and X-ray diffraction (XRD). A laboratory jar test was employed for the experiments. Process kinetic was studied to determine coagulation-flocculation parameters such as coagulation rate constant and coagulation half-life τ1/2. The effects of the operating parameters such as initial pH of the wastewater, coagulant dosage and settling time affecting the efficiency of turbidity removal were studied in a one-factor-at-a-time (OFAT) process. Box-Behnken Design (BBD) was used in designing the experiment; evaluate the individual and interactive effect of the variables and determining the optimum conditions. Statistical parameters such as coefficient of determination R2, sum of square roots due to error (SSE) and the root mean square error (RMSE) were used to evaluate the adequacy of the process. The optimum removal of turbidity was observed at pH range 2–4, dosage 100–200 mg/L and settling time of 30 min for the coagulants, with removal efficiency of 60–92.6% a second order polynomial regression equation with R2 values of 0.9644, 0.9827, 0.9707 and 0.9718 for OSC, DMC, CYC and ODC, respectively. While the coagulation half-time, τ1/2 ranges from 0.98 for OSC, 0.87 for DMC, 13.73 for CYC and 9.15 for ODC. The study has proved the coagulant can be used in treatment of turbidity from paint wastewater.