Optimisation and Modelling of Pb (II) and Cu (II) Biosorption onto Red Algae (Gracilaria changii) by Using Response Surface Methodology

The removal of Pb (II) and Cu (II) ions by using marine red macroalgae (Gracilaria changii) as a biosorbent material was evaluated through the batch equilibrium technique. The effect of solution pH on the removal of metal ions was investigated within the range of 2–7. The response surface methodology (RSM) technique involving central composite design (CCD) was utilised to optimise the three main sorption parameters, namely initial metal ion concentration, contact time, and biosorbent dosage, to achieve maximum ion removal. The models’ adequacy of response was verified by ANOVA. The optimum conditions for removal of Pb (II) and Cu (II) were as follows: pH values of 4.5 and 5, initial concentrations of 40 mg/L, contact times of 115 and 45 min, and biosorbent dosage of 1 g/L, at which the maximum removal percentages were 96.3% and 44.77%, respectively. The results of the adsorption isotherm study showed that the data fitted well with the Langmuir’s model for Pb (II) and Cu (II). The results of the adsorption kinetic study showed that the data fitted well with the pseudo-second order model for Pb (II) and Cu (II). In conclusion, red alga biomass exhibits great potential as an efficient low-cost sorbent for removal of metal ions.

In-vitro biocompatibility testing of phycobiliproteins from Gracilaria changii

The present study probes into the biocompatibility testing of Phycobiliproteins (PBPs) from Gracilaria changii, in-vitro. The cell survivability and cytotoxicity of PBPs to cultured Human Cervix Carcinoma (Hep-2C) cells were tested and observed using MTT (3-(4, 5- Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay. For ten-fold dilutions, Phycobiliproteins (PBPs) promotes highest cell survivability at 10-4 dilution rate with 239.62% and highest cytotoxic effect, with 40.21%, at 10-1 dilution. The compositions of phycobiliproteins were determined using Ultraviolet (UV-Vis) spectrophotometer giving visible absorbance peaks at 498.5, 614 and 651 nm for the three PBPs composition: Phycoerythrin (PE), Phycocyanin (PC) and Allophycocyanin (APC), respectively. The effects of time duration in centrifugation process of Phycobiliproteins (PBPs) from Gracilaria changii in 3, 5 and 7 minutes, were proven significant on the quantity of the extracted PBPs. The highest average concentration of 20.37 µg/ml for APC, 13.31 µg/ml for PC and 18.57 µg/ml for PE were obtained at the 5 minute-extraction process.