Woollen nonwovens

Concerning the cleaning of industrial sewage, both national and international standards are high. A nonwoven of reclaimed fibres is good value and functional, and can substitute for costly synthetic fibre materials. The nonwoven can be used to adsorb heavy metal ions (Pb(+2) ions, Cu(+2) ions, Zn(+2) ions), acid dyes (C.l. acid red 27, C.l. acid red 88) and oils (basic oil SN 150, diesel, crude oil). This requires a particular kind of surface modification treatment. For example, the woollen nonwoven is treated with biopolymer chitosan and low temperature plasma to ensure that heavy metals are better adsorbed. Investigations have shown that woollen reclaimed fibres are especially well suited to adsorb Pb (+2) ions. The adsorption of copper and zinc is also clearly improved through chitosan and plasma treatment. 

Woollen nonwovens are useful in absorbing oil films on water surfaces. ... 

Although widely used in dust collection, nonwoven fabrics have found only limited use in liquid filtration because their thickness and density render them prone to blinding in many applications. One area where they have found some success, however, has been in the filtration of metal ore concentrates such as copper on horizontal vacuum belt filters. These applications tend to be very aggressive on the filter fabric, and hence a suitably designed and finished nonwoven fabric is often more cost effective than a considerably more expensive woven fabric, especially if required in lengths of around 80 m and widths up to 6 m. The solids which are captured in such applications quickly form a cake on the surface and, should some penetration occur, as with woollen spun yams, the bulky nature of the material provides scope for the particles to escape. For such arduous applications, nonwoven fabrics are generally in the area density range of 800-1000 gm- ... 

Woollen felt is probably the oldest form of textile, and for many years was the only practical nonwoven fabric, produced by the combined action of moisture and heat on carded wool fibres. The development first of a strong adhesive-bonded felt, and then of the multiplicity of forms of dry-laid synthetic fibres, has transformed the spectrum of nonwoven media, both in format and basic material. 

---