The bentonite is a widely available and abundant natural mineral, and can be a low cost adsorbent for water and wastewater treatment. This study reported here was directed towards identifying a cost-effective activation protocol for enhancing the adsorption capacity of Australian bentonite for removal of toxic contaminants in wastewater. We investigated three protocols including thermal activation (TA), acid activation (AA), and combined acid and thermal activation (ATA). The results showed that these activation protocols under designed conditions can enhance the surface area and porosity of the raw bentonite. The best ATA protocol considered here brought a 70% increase in the surface area compared to 65% and 20% for the best AA and TA protocols, respectively. The optimal ATA protocol identified in the study leads to approximately 25% increase in the Congo-red adsorption capacity of the activated bentonite. This activation method could be a cost-effective approach to enhance the adsorption capacity, applicability and selectivity of natural clay materials, making them as promising and low cost adsorbents for wastewater treatment.

This work aimed to demonstrate the effect of optimised coagulation on minimise fouling for coagulation-ultrafiltration process. Coagulation as pretreatment has the potential to mitigate fouling and enhance flux. Operating parameters were tested by a matrix of experiments for various mixing conditions and coagulant doses. In coagulation experiments, varied shear forces were applied to generate different floc characteristics in order to assess the effect on membrane fouling. Floc properties were investigated with an optical monitoring technique to identify structure, size and growth of flocs. It was shown that stronger flocs are of advantage for fouling mitigation and that the coagulant dosage is crucial for the performance of filtration. The impact of water quality was assessed using general water quality parameters and organic characterisation techniques to investigate the performance of each treatment step. The treatment efficiency was further assessed based on comparing the molecular size fractions of the organic matter before and after coagulation using a size exclusion chromatography technique. The result confirmed the significance of organic character on treatment performance.

The biosorption of eight aromatic compounds with different functional groups by Penicillium oxalicum biomass were investigated. The affinity of the biomass for the eight compounds at pH 6.0 follows the following trend: 1-naphthalenamine>naphthol>benzoic acid>p-toluidine>p-cresol>p-toluic acid>phenol>p-toluenesulfonic acid. Biomass surface was characterized, and it was found that four discrete binding sites, corresponding to carboxyl (pKa=4.0), phosphoric (pKa=7.0), amine (pKa=8.8), and hydroxyl groups (pKa=10.0), were identified on the biomass surface by using the linear programming method (LPM) for the fitting of the titration data and FTIR analysis. The carboxyl and amine groups dominate the biomass surface sites, which might have played an important role in biosorption of organic compounds. Furthermore, the compounds were divided into two groups based on the calculation of ionization degree for toluene derivatives and the comparison on the number of benzene rings for barely ionized compounds. It was found that low ionization degree and high hydrophobicity favor the biosorption for the two groups, respectively. Moreover, a Radj2 of 0.724 between the log of Freundlich coefficient (logKf) and logKow indicated that the hydrophobicity plays role in the sorption of eight organic compounds. The QSAR model with one variable was developed for the first time between logKf and polar surface area (PSA) to predict the biosorption behaviors of organic compounds (Radj2=0.960) except for p-toluenesulfonic acid (with pKa<0), which also supported the electrostatic attraction and hydrophobicity mechanisms.

In this study, a microporous layer photocatalyst of titania nanocrystallites heterocoagulated with structurally modified kaolin (TiO2–K) was synthesised via a modified sol–gel method. Physical properties (particle size, morphology, stability and settleability) and photodegradation capacity of the TiO2–K catalyst subject to its synthesis, regeneration and use for water treatment were studied. The modified kaolin, as a support for the titania nanocrystallites had a delaminated sandwich silica structure that minimises chemical intercalation within the nanocomposite structure. Microscopic examination revealed that the TiO2 nanocrystallites were uniformly deposited on the kaolin external surface, resulting in a high degree of photon activation. Compared to the commercial TiO2 P25, the TiO2–K demonstrated a superior photocatalytic degradation capacity to remove an anionic Congo red dye. Its removal efficiency and photo-reaction performance were improved when the TiO2–K was regenerated by a thermal treatment. The TiO2–K particles can be easily separated from the water system for further reuse. This unique nanocomposite photocatalyst shows promising technical advantages for a continuous industrial process of water treatment.

The semiconductor photocatalysis technology has been known as a "green" approach and/or "zero" waste solution for the elimination of organic and microbial pollutants in water. Nanoscale TiO(2) has received great attention in R&D as a promising photocatalyst. Application of the photocatalysis technology for an industrial water treatment process is still being impeded by a number of technical challenges. This chapter provides an overview on the development of a novel titania impregnated kaolinite (TiO(2)/K) photocatalyst and an annular slurry photoreactor (ASP) system. We will introduce the overall results from our recent engineering science research, including synthesis and characterisation of the TiO(2)/K photocatalyst, hydrodynamic analysis of the ASP system, evaluation of photo-degradation kinetics, and application of statistical and modelling method for the optimization of the ASP-TiO(2)/K water treatment process.

In this study, two of our recently developed laboratory scale wastewater treatment systems, fluidised-bed reactor (FBR) using formulated clay mixture absorbents (clay-FBR adsorption) and an annular slurry photoreactor (ASP) using TiO2 impregnated kaolin catalysts (TiO2-K-ASP) were integrated as an adsorption–photocatalysis hybrid process to treat municipal wastewater as alternative secondary and tertiary treatment for wastewater reclamation. Primary effluent from sewage and secondary effluent from a membrane bioreactor treatment process were used to assess chemical removal capabilities of the FBR and ASP systems, and the hybrid process. The formulated clays-FBR system demonstrated the prevailing removal efficiency toward PO43−, NO3− and suspended solids. The TiO2-K-ASP showed superior degradation of dissolved organic content; while the presence of inorganic ions caused a detrimental effect on its performance. The integration of the adsorption and degradation system as a hybrid treatment process resulted in a synergetic enhancement for the chemical removal efficiency. Complete elimination of PO43− content was obtained in the adsorption stage; while 30% and 65% NO3− removal were obtained from the hybrid treatment of the primary and secondary effluents, respectively. The corresponding COD reduction during the photodegradation was further investigated by the high-performance size exclusion chromatography technique, where it revealed the shift of apparent molecular weight of the dissolved organic contaminants toward the smaller region. This present study demonstrated that this adsorption–photocatalysis hybrid technology can be used as a feasible alternative treatment process for wastewater reclamation.

This study was to determine the prospective application of a newly developed fluidised bed reactor (FBR) system using a formulated clay–lime mixture for a large-scale wastewater treatment implementation. A lab-made FBR was designed to assess the application of this formulated clay–lime mixture for the removal of several potential pollutants present in wastewater streams. The operating conditions of the FBR system was first optimised in batch mode by individual experiments prior to progressing into the continuous scheme. The results revealed that the dye elimination was enhanced significantly, by which 99% removal of 30mgL−1 dye can be achieved with 0.8gL−1 loading and aeration rate of 1Lmin−1. This process was found effective in removal of anionic dye and phosphate while less favourable towards nitrate. This can be attributed to the different dominant removal mechanisms i.e. precipitation and adsorption. The potential reaction time of the formulated clay–lime mixture was found to be pH dependent where the removal performance was superior in strong alkaline conditions. Several municipal primary effluent samples were also treated using the developed FBR system in continuous operation mode. This system contributed an average 10–15% and 20–40% reduction of the nitrate and COD, respectively, while 100% removal of phosphate was obtained over the experimental period. This study demonstrated that the developed FBR system with the formulated clay–lime mixture can be a cost-effective alternative treatment process for a large-scale application for the treatment of industrial wastewater.

We explored a feasible approach to enhance removal capacity of three natural clays for removing anionic dye from aqueous solution. Optimal mixing proportions of the clay materials and temperature range for the calcination were investigated. We found that the removal efficiency can be improved significantly when the clay materials were mixed at certain ratio with the addition of lime and the mixed clay materials were calcined 100-300 degrees C. Batch experiments were conducted to study the effects of initial concentration, material dosage, contact time and pH on dye elimination. Kinetic study showed that more than 80% dye removal took place in 5 min. A high removal capacity (>575 mg g(-1)) of the mixed clay materials can be achieved at a low adsorbent dose. The mixed clay materials can be easily recovered by thermal treatment. The recovered mixtures demonstrated an enhanced removal capability after a few cycles of removal and regeneration. The results revealed that use of these clay materials could develop a low-cost treatment process for industrial wastewater.

This study was to evaluate the adsorption capability of clay minerals of bentonite, kaolin and zeolite to remove Congo Red from aqueous solution. The experiments were carried out in a batch system to optimise operation variables: adsorbent dosage, Congo Red concentration, pH and temperature. Adsorption kinetic and equilibrium isotherm of the clay materials were studied using pseudo-first order and second order kinetic equations, and Freundlich and Langmuir models. The equilibrium data of kaolin was found to best fit to the Langmuir model, while bentonite and zeolite were best explained by the Freundlich model. The adsorption kinetic followed the pseudo-second order equation for the three adsorbents. Intra-particle diffusion studies revealed that the adsorption rates were not solely controlled by the diffusion step. Further thermodynamic investigations showed that the adsorption is an exothermic and spontaneous process. Sodium bentonite demonstrated the best adsorptive capacity followed by kaolin clay, and they can be employed as low-cost alternatives for recalcitrant dye removal from industrial wastewater.

Nano-sized titanium dioxide (TiO2) has received a great attention in the field of research and development as a promising photocatalyst to promote the degradation of organic contaminants in water. One of the key technical challenges involved in separation and recovery of the photocatalyst particles from the water treatment system makes this technology unviable as an industrial process. A novel titania impregnated kaolinite (TiO2/K) photocatalyst was synthesized by a modified two step sol–gel method: hydrolysis of titanium(IV) butoxide and heterocoagulation with pre-treated kaolinite (K) clay. The TiO2/K photocatalysts were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET specific surface area measurements (BET). The photocatalytic activity was evaluated by the degradation of Congo red in aqueous solution. The TiO2/K photocatalyst had a rigid porous layer structure and promising nano-size properties, and demonstrated an enhanced adsorption and photocatalytic ability for the removal of Congo red. The TiO2/K photocatalyst can be easily separated and recovered from the water treatment system. The TiO2/K photocatalyst is expected to deliver a true engineering solution for an industrial water/wastewater treatment process.

Our recent work reported that a mixed adsorbent with natural clay materials and lime demonstrated an enhanced capacity and efficiency to remove anionic Congo Red dye from wastewater. This study aims to investigate the removal kinetic and mechanisms of the mixed materials involved in the decolourisation of the dye to maximise their prospective applications for industrial wastewater treatment. The experimental results showed that dye removal was governed by combined physiochemical reactions of adsorption, ion-exchange, and precipitation. Ca-dye precipitation contributed over 70% total dye removal, followed by adsorption and ion-exchange. The dye removal kinetic followed the pseudo-second-order expression and was well described by the Freundlich isotherm model. This study indicated pH was a key parameter to govern the removal mechanisms, i.e. adsorption/coagulation at acidic pH and precipitation at basic condition. Yet, the overall removal efficiency was found to be independent to the operation conditions, resulting in more than 94% dye removal. This work revealed that the mixed clays and lime can be applied as alternative low-cost adsorbents for industrial wastewater treatment.

This study investigated the potential use of kaolin as alternative adsorbents for removal of congo red from wastewater. The effect of adsorbent dosage, dye concentration, pH and temperature were experimentally studied to evaluate the adsorption capacity, kinetics and equilibrium. Experimental results revealed that optimal adsorption took place at acidic pH and high dye concentration. Ceram kaolin had the highest removal efficiency among studied kaolins, followed by K15GR and Q38. The dye uptake process obeyed the pseudo-second order kinetic expression and was best described by the Langmuir isotherm. Intra-particle diffusion studies showed that the adsorption mechanism was not exclusively controlled by the diffusion step and was more likely to be governed by external mass transfer. Thermodynamic studies showed congo red adsorption on all kaolins was exothermic and spontaneous in nature. Recovered Q38 and K15GR kaolin demonstrated an enhanced adsorption capability. The results indicate that these local kaolins could be employed as low-cost alternatives for removal of anionic dyes from industrial wastewater.

1,4-dioxane is a synthetic compound found in industrial effluent and subsequently contaminates water bodies due to its high solubility and high volatility. It is of concern due to its toxic and hazardous nature and has been listed as a class 2B carcinogen. This study involved optimisation of the photocatalytic and H2O2/UVC processes for 1,4-dioxane removal. Different photocatalysts and loadings were investigated for the degradation of low concentrations of 1,4-dioxane in water including a commercial P25, a synthesised magnetic photocatalyst and an immobilised sol–gel system. A commercial catalyst (Degussa P25) was the most efficient. A lifetime study of the sol–gel reactor showed that the coating was stable over the time period studied. The optimum H2O2 concentration in the H2O2/UVC process was found to be 30ppm. The addition of H2O2 to the photocatalytic process for 1,4-dioxane removal caused a decrease in rate for the commercial P25 photocatalyst and an increase in rate for the lab-made magnetic photocatalyst.

This research involves the removal of contaminants of concern in water supplies using advanced oxidation technologies, in particular titanium dioxide photocatalysis. Photocatalysis for the removal of 1,4-dioxane and the natural (17 beta-oestradiol, oestriol) and synthetic (17 alpha-ethynyloestradiol) oestrogens in water was investigated using both UVA and solar radiation. The H2O2/UVC process, solar, UVC and UVA light alone were also investigated and the processes compared. It was found that TiO2 photocatalysis is an effective method for the degradation of the natural (17 beta-oestradiol and oestriol) and the synthetic (17 alpha-ethynyloestradiol) oestrogens in water in immobilised Degussa P25 and sol-gel spiral reactors with both UVA and solar radiation as the light source. Photocatalysis using the commercial catalyst Degussa P25 as an immobilised reactor with a UVA lamp shows the best performance. Photocatalysis was shown to completely mineralise 1,4-dioxane to CO2 in Degussa P25 suspension and sol-gel reactors using both UVA and solar radiation. The commercial catalyst Degussa P25 in suspension with UVA radiation shows the best performance. Photocatalysis is much more efficient than H2O2/UVC, UVA, UVC and solar radiation alone for all contaminants investigated.