The adsorption of the divalent cations of Cu, Zn, Cd and Pb by tea leaves and coffee grounds from aqueous solutions is described. Both adsorbents exhibited strong affinity for these ions which could be described by a simple single-site equilibrium model. For coffee, the order of increasing adsorption equilibrium constant K was Cu < Pb < Zn < Cd, while for tea the opposite order was observed indicating that the adsorption sites on each adsorbent have a different chemical nature. Adsorption decreased at low pH < 4 through competition with H+ for adsorption sites, and for all metals except Cu, at high pH > 10, probably because of anion formation in the case of Zn2+ and also increased leaching of metal-binding soluble materials. The effect of metal ion concentration on the adsorptive equilibria indicated a threshold concentration above which overall adsorption became limited by saturation of the adsorption sites. Competition between two metal ions for the same sites was not observed with Cu(II) and Pb(II), however Zn(II) reacted competitively with Cd(II) binding sites on both tea and coffee. If fresh coffee or tea adsorbents were used, the fraction of metal ion taken up by the adsorbent was diminished by the competitive effects of soluble metal-binding ligands released by the tea or coffee. Experiments with coffee showed that roasting temperature controls the formation of metal ion adsorption sites for this adsorbent.

The adsorption of the heavy metal ions Cu 2+ , Zn 2+ , Cd 2+ and Pb 2+ from aqueous solution by used coffee grounds has been investigated as a potential low-cost treatment method for heavy metal-containing waste waters that is based on a readily available natural by-product. The results show that metal ion adsorption is efficient over a fairly wide pH range and adsorbed metals are reversibly leached from the exhausted coffee by dilute acid without significant loss of the adsorptive capacity for subsequent re-use.

Methylene Blue (MB) has been found to be one of the most common dyes used in the industries. Adsorption process using Activated Carbon (AC) has been proven to be able to remove MB effectively but the treatment cost using the adsorbent is considered expensive due to its high energy cost. Sugarcane Bagasse (SGB) is an agricultural by-product and abundantly available material in many developing countries. FTIR and XRD were used to confirm the existence of ligno-cellulose content of SGB after experiencing various chemical treatments. SGB had 5 -40 folds higher MB removal capability than commercial activated carbon, depending on the pH of water medium and the type of SGB. SGB showed a much better performance in adsorbing MB in alkaline environment than in acidic environment. Langmuir adsorption isotherm model was able to estimate the removal capacity of non-chemical treated SGB (NSGB) and CaCl2 treated SGB (CSGB) at 84.7458 mg/g and 35.2113 mg/g respectively. An extremely higher MB removal capacity was found for BSGB due to the complexity of the surface site after chemical treatment. NaOH treated SGB (BSGB) with low lignin residue content was the most favourable adsorbent for MB adsorption.

Discharging wastewater containing heavy metals of Cu, Pb, Zn and Cd into water bodies can cause toxicity in plants and aquatic animals and some of them will be unable to survive except algae. Wastewater treatment method to remove heavy metal contaminants includes chemical precipitation, ion exchange, membrane, filtration, adsorption using activated carbon. However, these methods are either expensive or have other disadvantages such as high energy consumption and inefficiencies when existing heavy metals are at trace concentration. Biosorption using algae biomass can be an alternative method to eliminate heavy metals. The objective of the project is to investigate the capability of Marine Algae (MA) and Freshwater Algae (FA) biomass in adsorbing heavy metals of Cu, Pb, Zn and Cd from water medium using synthetic water and industrial water. MA and FA were obtained from the eastern coast of Pulau Ubin and local fish farm respectively. After being fully washed with deionised water, dried in a furnace for 105˚C, they are grinded to pass 1 mm 2 of siever. MA and FA were characterised using FTIR to determine their functional groups. An industrial water was collected from industrial discharge from metal factories in northern side of Singapore. Effect of adsorption time, adsorbent concentration, and pH were studied. The result showed that FA and MA had a higher capability in adsorbing a total metal of about 40 ppm level from an industrial water, or 4 times than synthetic water concentration, at the same adsorbent dosage of 50 mg. In conclusion, the presence of various functional groups, hydroxyl, carboxylic and amine groups, in all MA and FA samples had enabled the algae biomass to adsorb heavy metals of Cu, Pb, Cd and Zn from synthetic and industrial water. Due to their biosorptive properties and fast adsorption capability, algae could be a potential method for cleaning up surface water or post-treatment of wastewater and minimise the cost of eutrophication.

Silica aerogels are light weight, nanostructured, and highly porous materials with an open pore structure. Due to their excellent characteristics, such as extremely low thermal conductivity, low density and high porosity, the silica aerogels become promising potential adsorbents, catalysts, thermal insulation, and acoustic absorption materials for environmental purposes. This paper presents the synthesis of a highly flexible polymer modified silica aerogel with the use of a cellulose-methyltriethoxysilane (MTES) precursor in a two-step acid-base catalyzed sol-gel process. The physical properties of the resulting aerogels were characterized by thermogravimetry, scanning electron microscopy, nitrogen adsorption-desorption, contact angle, thermal conductivity measurements, compression testing and Fourier transform infrared spectroscopy. The fabricated aerogel exhibited high flexibility with a Young's modulus of compression of 0.33 MPa and the density of 0.132 g/cm 3. They were hydrophobic in nature and had low thermal conductivity. Preparation of aerogel with solid waste (fly ash/bottom ash) is also discussed. The preliminary results showed that the materials have great potential for environmental application, i.e. enhancement of solid waste recycling rate by converting waste to high value-added materials, super thermal and acoustic insulation materials in green building and removal of oil spilled into surface drainage.